Subjects -> CHEMISTRY (Total: 986 journals)
    - ANALYTICAL CHEMISTRY (59 journals)
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CHEMISTRY (713 journals)                  1 2 3 4 | Last

Showing 1 - 200 of 735 Journals sorted alphabetically
Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement     Hybrid Journal   (Followers: 29)
ACS Applied Polymer Materials     Hybrid Journal   (Followers: 9)
ACS Catalysis     Hybrid Journal   (Followers: 51)
ACS Chemical Neuroscience     Hybrid Journal   (Followers: 21)
ACS Combinatorial Science     Hybrid Journal   (Followers: 21)
ACS Macro Letters     Hybrid Journal   (Followers: 25)
ACS Materials Letters     Open Access   (Followers: 2)
ACS Medicinal Chemistry Letters     Hybrid Journal   (Followers: 43)
ACS Nano     Hybrid Journal   (Followers: 189)
ACS Photonics     Hybrid Journal   (Followers: 15)
ACS Symposium Series     Full-text available via subscription   (Followers: 3)
ACS Synthetic Biology     Hybrid Journal   (Followers: 28)
Acta Chemica Malaysia     Open Access  
Acta Chimica Slovaca     Open Access   (Followers: 2)
Acta Chimica Slovenica     Open Access   (Followers: 2)
Acta Chromatographica     Full-text available via subscription   (Followers: 7)
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 8)
Acta Scientifica Naturalis     Open Access   (Followers: 2)
adhäsion KLEBEN & DICHTEN     Hybrid Journal   (Followers: 7)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 9)
Advanced Electronic Materials     Hybrid Journal   (Followers: 5)
Advanced Functional Materials     Hybrid Journal   (Followers: 70)
Advanced Journal of Chemistry, Section A     Open Access   (Followers: 3)
Advanced Journal of Chemistry, Section B     Open Access   (Followers: 1)
Advanced Science Focus     Free   (Followers: 5)
Advanced Theory and Simulations     Hybrid Journal   (Followers: 2)
Advanced Therapeutics     Hybrid Journal   (Followers: 1)
Advances in Chemical Engineering and Science     Open Access   (Followers: 104)
Advances in Chemical Science     Open Access   (Followers: 50)
Advances in Chemistry     Open Access   (Followers: 34)
Advances in Chemistry     Full-text available via subscription   (Followers: 4)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 16)
Advances in Environmental Chemistry     Open Access   (Followers: 9)
Advances in Enzyme Research     Open Access   (Followers: 10)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 8)
Advances in Materials Physics and Chemistry     Open Access   (Followers: 31)
Advances in Nanoparticles     Open Access   (Followers: 17)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 18)
Advances in Polymer Science     Hybrid Journal   (Followers: 50)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 18)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 6)
Advances in Science and Technology     Full-text available via subscription   (Followers: 16)
Aerosol Science and Engineering     Hybrid Journal  
African Journal of Bacteriology Research     Open Access  
African Journal of Chemical Education     Open Access   (Followers: 5)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 6)
Aggregate     Open Access  
Agrokémia és Talajtan     Full-text available via subscription   (Followers: 2)
Al-Kimia : Jurnal Penelitian Sains Kimia     Open Access  
Alchemy : Journal of Chemistry     Open Access   (Followers: 3)
Alchemy : Jurnal Penelitian Kimia     Open Access  
Alotrop     Open Access  
AMB Express     Open Access   (Followers: 1)
Ambix     Hybrid Journal   (Followers: 3)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 43)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 19)
American Journal of Chemistry     Open Access   (Followers: 37)
American Journal of Plant Physiology     Open Access   (Followers: 7)
Analyst     Hybrid Journal   (Followers: 36)
Analytical Science Advances     Open Access   (Followers: 1)
Angewandte Chemie     Hybrid Journal   (Followers: 155)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 227)
Annales Universitatis Mariae Curie-Sklodowska, sectio AA – Chemia     Open Access   (Followers: 1)
Annals of Clinical Chemistry and Laboratory Medicine     Open Access   (Followers: 6)
Annual Reports in Computational Chemistry     Full-text available via subscription   (Followers: 4)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 12)
Annual Review of Food Science and Technology     Full-text available via subscription   (Followers: 14)
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 7)
Applied Surface Science     Hybrid Journal   (Followers: 30)
Arabian Journal of Chemistry     Open Access   (Followers: 4)
ARKIVOC     Open Access   (Followers: 1)
Asian Journal of Applied Chemistry Research     Open Access   (Followers: 1)
Asian Journal of Biochemistry     Open Access   (Followers: 2)
Asian Journal of Chemical Sciences     Open Access   (Followers: 1)
Asian Journal of Chemistry and Pharmaceutical Sciences     Open Access  
Asian Journal of Physical and Chemical Sciences     Open Access   (Followers: 2)
Atomization and Sprays     Full-text available via subscription   (Followers: 7)
Australian Journal of Chemistry     Hybrid Journal   (Followers: 7)
Autophagy     Hybrid Journal   (Followers: 7)
Avances en Quimica     Open Access  
Biochemical Pharmacology     Hybrid Journal   (Followers: 11)
Biochemistry     Hybrid Journal   (Followers: 203)
Biochemistry Research International     Open Access   (Followers: 5)
BioChip Journal     Hybrid Journal  
Bioinorganic Chemistry and Applications     Open Access   (Followers: 5)
Biointerface Research in Applied Chemistry     Open Access  
Biointerphases     Open Access   (Followers: 1)
Biology, Medicine, & Natural Product Chemistry     Open Access   (Followers: 2)
Biomacromolecules     Hybrid Journal   (Followers: 22)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 10)
Biomedical Chromatography     Hybrid Journal   (Followers: 6)
Biomolecular NMR Assignments     Hybrid Journal   (Followers: 3)
BioNanoScience     Partially Free   (Followers: 3)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 93)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 66)
Bioorganic Chemistry     Hybrid Journal   (Followers: 9)
Biopolymers     Hybrid Journal   (Followers: 15)
Biosensors     Open Access   (Followers: 3)
Biotechnic and Histochemistry     Hybrid Journal   (Followers: 1)
Bitácora Digital     Open Access  
Boletin de la Sociedad Chilena de Quimica     Open Access  
Bulletin of Institute of Chemistry and Chemical Technology, Mongolian Academy of Sciences     Open Access  
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 1)
Bulletin of the Chemical Society of Japan     Full-text available via subscription   (Followers: 24)
Bulletin of the Korean Chemical Society     Hybrid Journal   (Followers: 1)
C - Journal of Carbon Research     Open Access   (Followers: 5)
Cakra Kimia (Indonesian E-Journal of Applied Chemistry)     Open Access  
Canadian Journal of Chemistry     Hybrid Journal   (Followers: 12)
Canadian Mineralogist     Full-text available via subscription   (Followers: 5)
Carbohydrate Polymer Technologies and Applications     Open Access  
Carbohydrate Polymers     Hybrid Journal   (Followers: 8)
Carbohydrate Research     Hybrid Journal   (Followers: 24)
Carbon     Hybrid Journal   (Followers: 65)
Carbon Capture Science & Technology     Open Access   (Followers: 5)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 9)
Catalysis Science and Technology     Hybrid Journal   (Followers: 9)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 4)
Catalysts     Open Access   (Followers: 11)
Cell Reports Physical Science     Open Access  
Cellulose     Hybrid Journal   (Followers: 8)
Cereal Chemistry     Full-text available via subscription   (Followers: 4)
Chem     Hybrid Journal   (Followers: 9)
Chem Catalysis     Hybrid Journal   (Followers: 6)
ChemBioEng Reviews     Full-text available via subscription   (Followers: 3)
ChemCatChem     Hybrid Journal   (Followers: 8)
Chemical and Engineering News     Free   (Followers: 21)
Chemical Bulletin of Kazakh National University     Open Access  
Chemical Communications     Hybrid Journal   (Followers: 81)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 25)
Chemical Physics Impact     Full-text available via subscription   (Followers: 5)
Chemical Research in Chinese Universities     Hybrid Journal   (Followers: 4)
Chemical Research in Toxicology     Hybrid Journal   (Followers: 22)
Chemical Reviews     Hybrid Journal   (Followers: 176)
Chemical Science     Open Access   (Followers: 39)
Chemical Science International Journal     Open Access  
Chemical Technology     Open Access   (Followers: 74)
Chemical Thermodynamics and Thermal Analysis     Open Access   (Followers: 7)
Chemical Vapor Deposition     Hybrid Journal   (Followers: 4)
Chemie in Unserer Zeit     Hybrid Journal   (Followers: 54)
Chemie-Ingenieur-Technik (Cit)     Hybrid Journal   (Followers: 21)
ChemInform     Hybrid Journal   (Followers: 5)
Chemistry & Biodiversity     Hybrid Journal   (Followers: 7)
Chemistry & Industry     Full-text available via subscription   (Followers: 6)
Chemistry - A European Journal     Hybrid Journal   (Followers: 125)
Chemistry - An Asian Journal     Hybrid Journal   (Followers: 19)
Chemistry Africa : A Journal of the Tunisian Chemical Society     Hybrid Journal  
Chemistry and Materials Research     Open Access   (Followers: 17)
Chemistry Central Journal     Open Access   (Followers: 4)
Chemistry Education Research and Practice     Free   (Followers: 6)
Chemistry Education Review     Open Access   (Followers: 1)
Chemistry in Education     Open Access   (Followers: 3)
Chemistry Letters     Full-text available via subscription   (Followers: 44)
Chemistry of Heterocyclic Compounds     Hybrid Journal   (Followers: 5)
Chemistry of Materials     Hybrid Journal   (Followers: 160)
Chemistry of Natural Compounds     Hybrid Journal   (Followers: 10)
Chemistry World     Hybrid Journal   (Followers: 20)
Chemistry-Didactics-Ecology-Metrology     Open Access  
ChemistryOpen     Open Access   (Followers: 1)
ChemistrySelect     Hybrid Journal   (Followers: 1)
Chemistry–Methods     Open Access   (Followers: 1)
Chemkon - Chemie Konkret, Forum Fuer Unterricht Und Didaktik     Hybrid Journal  
ChemNanoMat     Hybrid Journal   (Followers: 1)
Chemoecology     Hybrid Journal   (Followers: 2)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 13)
ChemPhotoChem     Hybrid Journal  
ChemPhysChem     Hybrid Journal   (Followers: 12)
ChemPhysMater     Full-text available via subscription   (Followers: 8)
ChemPlusChem     Hybrid Journal   (Followers: 2)
Chempublish Journal     Open Access  
ChemSystemsChem     Hybrid Journal   (Followers: 1)
ChemTexts     Hybrid Journal   (Followers: 1)
CHIMIA International Journal for Chemistry     Open Access   (Followers: 2)
Chinese Journal of Chemistry     Hybrid Journal   (Followers: 6)
Chinese Journal of Polymer Science     Hybrid Journal   (Followers: 9)
Chromatographia     Hybrid Journal   (Followers: 22)
Chromatography     Open Access   (Followers: 2)
Chromatography Research International     Open Access   (Followers: 4)
Ciencia     Open Access  
Clay Minerals     Hybrid Journal   (Followers: 7)
Cogent Chemistry     Open Access   (Followers: 3)
Colloid and Interface Science Communications     Open Access  
Colloid and Polymer Science     Hybrid Journal   (Followers: 6)
Colloids and Surfaces B: Biointerfaces     Hybrid Journal   (Followers: 8)
Combinatorial Chemistry & High Throughput Screening     Hybrid Journal   (Followers: 2)
Combustion Science and Technology     Hybrid Journal   (Followers: 26)
Comments on Inorganic Chemistry: A Journal of Critical Discussion of the Current Literature     Hybrid Journal   (Followers: 1)
Communications Chemistry     Open Access   (Followers: 2)
Communications Materials     Open Access  
Composite Interfaces     Hybrid Journal   (Followers: 6)
Comptes Rendus : Chimie     Open Access  
Comptes Rendus : Physique     Open Access   (Followers: 2)
Computational and Theoretical Chemistry     Hybrid Journal   (Followers: 11)
Computational Biology and Chemistry     Hybrid Journal   (Followers: 13)
Computational Chemistry     Open Access   (Followers: 4)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 11)
Coordination Chemistry Reviews     Full-text available via subscription   (Followers: 6)
Corrosion Communications     Open Access   (Followers: 5)
Critical Reviews in Biochemistry and Molecular Biology     Hybrid Journal   (Followers: 17)
Croatica Chemica Acta     Open Access  
CrystEngComm     Hybrid Journal   (Followers: 10)

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  • Chemistry, Vol. 3, Pages 1101-1112: Analysis of Local and Global
           Aromaticity in Si3C5 and Si4C8 Clusters. Aromatic Species Containing
           Planar Tetracoordinate Carbon

    • Authors: Juan J. Torres-Vega, Diego R. Alcoba, Ofelia B. Oña, Alejandro Vásquez-Espinal, Rodrigo Báez-Grez, Luis Lain, Alicia Torre, Víctor García, William Tiznado
      First page: 1101
      Abstract: The minimum energy structures of the Si3C5 and Si4C8 clusters are planar and contain planar tetracoordinate carbons (ptCs). These species have been classified, qualitatively, as global (π) and local (σ) aromatics according to the adaptive natural density partitioning (AdNDP) method, which is an orbital localization method. This work evaluates these species’ aromaticity, focusing on confirming and quantifying their global and local aromatic character. For this purpose, we use an orbital localization method based on the partitioning of the molecular space according to the topology of the electronic localization function (LOC-ELF). In addition, the magnetically induced current density is analyzed. The LOC-ELF-based analysis coincides with the AdNDP study (double aromaticity, global, and local). Moreover, the current density analysis detects global and local ring currents. The strength of the global and local current circuit is significant, involving 4n + 2 π- and σ-electrons, respectively. The latter implicates the Si-ptC-Si fragment, which would be related to the 3c-2e σ-bond detected by the orbital localization methods in this fragment.
      Citation: Chemistry
      PubDate: 2021-09-25
      DOI: 10.3390/chemistry3040080
      Issue No: Vol. 3, No. 4 (2021)
  • Chemistry, Vol. 3, Pages 1113-1125: Study on Adsorption Performance of
           Benzoic Acid in Cyclocarya paliurus Extract by Ethyl Cellulose

    • Authors: Yamin Zhao, Lujun Zhang, Xiaoxue Zhai, Qian Liu, Lebing Sun, Mengshi Liu, Lili An, Liang Xian, Ping Zhang, Lihua Chen
      First page: 1113
      Abstract: Polymer microspheres with inter-connecting pores are widely used as microsphere materials. In the study, the ethyl cellulose microspheres (ECM) were prepared by using the solvent-evaporation method. Based on that, a method for the separation and purification of benzoic acid from crude extract of Cyclocarya paliurus was established by the ECM and high performance liquid chromatography (HPLC). The ECM after the sorption equilibrium was desorbed by using 40% methanol as the analytical solvent. The content of benzoic acid in eluent is up to 0.0216 mg/mL, and the benzoic acid can be obtained with a high purity of 82.22%. Furthermore, the adsorption-desorption behavior of benzoic acid onto ECM was investigated. The results of adsorption kinetics of benzoic acid showed that the adsorption followed the pseudo-first-order kinetic model. The ECM was characterized by using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscope (SEM), and X-ray diffraction (XRD). The results showed that the ECM has a high adsorption property due to its more porous structure, phenolic hydroxyl group, and other oxygen-containing functional groups. This method and the ECM can be used stably, continuously, and efficiently to purify the benzoic acid from the methanol extract of C. paliurus on a large scale.
      Citation: Chemistry
      PubDate: 2021-10-01
      DOI: 10.3390/chemistry3040081
      Issue No: Vol. 3, No. 4 (2021)
  • Chemistry, Vol. 3, Pages 1126-1137: Q-Tube®-Assisted Alkylation and
           Arylation of Xanthines and Other N-H-Containing Heterocycles in Water

    • Authors: Cecilia Scimmi, Margherita Cardinali, Laura Abenante, Marina Amatista, Francesca Giulia Nacca, Eder J. Lenardao, Luca Sancineto, Claudio Santi
      First page: 1126
      Abstract: In this paper, a simple and clean process for the alkylation and arylation of nitrogen-containing heterocycles is reported. The reactions were conducted using the Q-tube® as a non-conventional technology, in water as a green solvent, at overboiling temperature. The developed strategy was used to improve two steps in the total synthesis of caffeine, as reported by Narayan, and then extended to the preparation of N-decorated xanthines. Finally, piperidine, methyl piperazine, and isatine were proven to be suitable substrates for the protocol proposed herein.
      Citation: Chemistry
      PubDate: 2021-10-01
      DOI: 10.3390/chemistry3040082
      Issue No: Vol. 3, No. 4 (2021)
  • Chemistry, Vol. 3, Pages 1138-1156: Partitioning Hückel–London Currents
           into Cycle Contributions

    • Authors: Wendy Myrvold, Patrick W. Fowler, Joseph Clarke
      First page: 1138
      Abstract: Ring-current maps give a direct pictorial representation of molecular aromaticity. They can be computed at levels ranging from empirical to full ab initio and DFT. For benzenoid hydrocarbons, Hückel–London (HL) theory gives a remarkably good qualitative picture of overall current patterns, and a useful basis for their interpretation. This paper describes an implemention of Aihara’s algorithm for computing HL currents for a benzenoid (for example) by partitioning total current into its constituent cycle currents. The Aihara approach can be used as an alternative way of calculating Hückel–London current maps, but more significantly as a tool for analysing other empirical models of induced current based on conjugated circuits. We outline an application where examination of cycle contributions to HL total current led to a simple graph-theoretical approach for cycle currents, which gives a better approximation to the HL currents for Kekulean benzenoids than any of the existing conjugated-circuit models, and unlike these models it also gives predictions of the HL currents in non-Kekulean benzenoids that are of similar quality.
      Citation: Chemistry
      PubDate: 2021-10-08
      DOI: 10.3390/chemistry3040083
      Issue No: Vol. 3, No. 4 (2021)
  • Chemistry, Vol. 3, Pages 1157-1165: Exploiting In-Situ Characterization
           for a Sabatier Reaction to Reveal Catalytic Details

    • Authors: Simon Yunes, Urim Pearl Kim, Hoang Nguyen, Jeffrey Kenvin
      First page: 1157
      Abstract: In situ characterization of catalysts provides important information on the catalyst and the understanding of its activity and selectivity for a specific reaction. TPX techniques for catalyst characterization reveal the role of the support on the stabilization and dispersion of the active sites. However, these can be altered at high temperature since sintering of active species can occur as well as possible carbon deposition through the Bosch reaction, which hinders the active species and deactivates the catalyst. In situ characterization of the spent catalyst, however, may expose the causes for catalyst deactivation. For example, a simple TPO analysis on the spent catalyst may produce CO and CO2 via a reaction with O2 at high temperature and this is a strong indication that deactivation may be due to the deposition of carbon during the Sabatier reaction. Other TPX techniques such as TPR and pulse chemisorption are also valuable techniques when they are applied in situ to the fresh catalyst and then to the catalyst upon deactivation.
      Citation: Chemistry
      PubDate: 2021-10-08
      DOI: 10.3390/chemistry3040084
      Issue No: Vol. 3, No. 4 (2021)
  • Chemistry, Vol. 3, Pages 1166-1177: Novel Approaches for Biocorrosion
           Mitigation in Sewer Systems

    • Authors: Georgios Fytianos, Dimitra Banti, Esmeralda Dushku, Efthimios Papastergiadis, Minas Yiangou, Petros Samaras
      First page: 1166
      Abstract: Concrete sewer pipes can be corroded by the biogenic sulfuric acid (H2SO4) generated from microbiological activities in a process called biocorrosion or microbiologically induced corrosion (MIC). In this study, inhibitors that can reduce Acidithiobacillus thiooxidans growth and thus may reduce the accumulation of biofilm components responsible for the biodegradation of concrete were used. D-tyrosine, tetrakis hydroxymethyl phosphonium sulfate (THPS) and TiO2 nanoparticles were investigated as potential inhibitors of sulfur-oxidizing bacteria (SOB) growth. Results showed that most of the chemicals used can inhibit SOB growth at a concentration lower than 100 mg/L. TiO2 nanoparticles exhibited the highest biocide effect and potential biocorrosion mitigation activity, followed by D-tyrosine and THPS.
      Citation: Chemistry
      PubDate: 2021-10-09
      DOI: 10.3390/chemistry3040085
      Issue No: Vol. 3, No. 4 (2021)
  • Chemistry, Vol. 3, Pages 1178-1188: Evaluation of the Anticancer and
           DNA-Binding Characteristics of Dichloro(diimine)zinc(II) Complexes

    • Authors: Bandar A. Babgi, Doaa Domyati, Magda H. Abdellattif, Mostafa A. Hussien
      First page: 1178
      Abstract: Several metal diimine complexes have been reported to possess anticancer properties. To evaluate the anticancer properties of tetrahedral zinc(II) diimine complexes, six complexes were synthesized with the general formula M(N^N)Cl2 {where M = Zn, Pt and N^N = 2,2’-biquinoline (1), 2,2’-dipyridylketone (2) and 4-((pyridine-2-ylmethylene)amino)phenol (3)}. In general, the intrinsic DNA-binding constants for the different compounds exhibited values within close proximity; the changes in the viscosity of the CT-DNA upon binding to the compounds suggest intercalation-binding mode. Molecular docking study predicted that complexes containing the highly planar ligand 2,2’-biquinoline are capable to establish π–π interactions with nucleobases of the DNA; the other four complexes engaged in donor–acceptor interactions with DNA nucleobases. The six complexes and two reference drugs (cisplatin and sunitinib) were tested against two cancer cell lines (COLO 205 and RCC-PR) and one normal cell line (LLC-MK2), highlighting the better performance of the zinc(II) complexes compared to their platinum(II) analogues. Moreover, zinc(II) complexes have higher selectivity index values than the reference drugs, with promising anticancer properties.
      Citation: Chemistry
      PubDate: 2021-10-11
      DOI: 10.3390/chemistry3040086
      Issue No: Vol. 3, No. 4 (2021)
  • Chemistry, Vol. 3, Pages 1189-1202: Dehydration of Fructose to
           5-Hydroxymethylfurfural: Effects of Acidity and Porosity of Different
           Catalysts in the Conversion, Selectivity, and Yield

    • Authors: João Pedro Vieira Lima, Pablo Teles Aragão Campos, Mateus Freitas Paiva, José J. Linares, Sílvia C. L. Dias, José A. Dias
      First page: 1189
      Abstract: There is a demand for renewable resources, such as biomass, to produce compounds considered as platform molecules. This study deals with dehydration of fructose for the formation of 5-hydroxymethylfurfural (HMF), a feedstock molecule. Different catalysts (aluminosilicates, niobic acid, 12-tungstophosphoric acid—HPW, and supported HPW/Niobia) were studied for this reaction in an aqueous medium. The catalysts were characterized by XRD, FT-IR, N2 sorption at −196 °C and pyridine adsorption. It was evident that the nature of the sites (Brønsted and Lewis), strength, quantity and accessibility to the acidic sites are critical to the conversion and yield results. A synergic effect of acidity and mesoporous area are key factors affecting the activity and selectivity of the solid acids. Niobic acid (Nb2O5·nH2O) revealed the best efficiency (highest TON, yield, selectivity and conversion). It was determined that the optimum acidity strength of catalysts should be between 80 to 100 kJ mol−1, with about 0.20 to 0.30 mmol g−1 of acid sites, density about 1 site nm−2 and mesoporous area about 100 m2 g−1. These values fit well within the general order of the observed selectivity (i.e., Nb2O5 > HZSM-5 > 20%HPW/Nb2O5 > SiO2-Al2O3 > HY > HBEA).
      Citation: Chemistry
      PubDate: 2021-10-12
      DOI: 10.3390/chemistry3040087
      Issue No: Vol. 3, No. 4 (2021)
  • Chemistry, Vol. 3, Pages 1203-1214: A Family of Externally-Functionalised
           Coordination Cages

    • Authors: Garrett D. Jackson, Max B. Tipping, Christopher G. P. Taylor, Jerico R. Piper, Callum Pritchard, Cristina Mozaceanu, Michael D. Ward
      First page: 1203
      Abstract: New synthetic routes are presented to derivatives of a (known) M8L12 cubic coordination cage in which a range of different substituents are attached at the C4 position of the pyridyl rings at either end of the bis(pyrazolyl-pyridine) bridging ligands. The substituents are (i) –CN groups (new ligand LCN), (ii) –CH2OCH2–CCH (containing a terminal alkyne) groups (new ligand LCC); and (iii) –(CH2OCH2)3CH2OMe (tri-ethyleneglycol monomethyl ether) groups (new ligand LPEG). The resulting functionalised ligands combine with M2+ ions (particularly Co2+, Ni2+, Cd2+) to give isostructural [M8L12]16+ cage cores bearing 24 external functional groups; the cages based on LCN (with M2+ = Cd2+) and LCC (with M2+ = Ni2+) have been crystallographically characterised. The value of these is twofold: (i) exterior nitrile or alkene substituents can provide a basis for further synthetic opportunities via ‘Click’ reactions allowing in principle a diverse range of functionalisation of the cage exterior surface; (ii) the exterior –(CH2OCH2)3CH2OMe groups substantially increase cage solubility in both water and in organic solvents, allowing binding constants of cavity-binding guests to be measured under an increased range of conditions.
      Citation: Chemistry
      PubDate: 2021-10-14
      DOI: 10.3390/chemistry3040088
      Issue No: Vol. 3, No. 4 (2021)
  • Chemistry, Vol. 3, Pages 1215-1246: A Comprehensive Review of
           Graphene-Based Anode Materials for Lithium-ion Capacitors

    • Authors: Dong Sui, Linqi Si, Changle Li, Yanliang Yang, Yongsheng Zhang, Weibo Yan
      First page: 1215
      Abstract: Lithium-ion capacitors (LICs) are considered to be one of the most promising energy storage devices which have the potential of integrating high energy of lithium-ion batteries and high power and long cycling life of supercapacitors into one system. However, the current LICs could only provide high power density at the cost of low energy density due to the sluggish Li+ diffusion and/or low electrical conductivity of the anode materials. Moreover, the serious capacity and kinetics imbalances between anode and cathode result in not only inferior rate performance but also unsatisfactory cycling stability. Therefore, designing high-power and structure stable anode materials is of great significance for practical LICs. Under this circumstance, graphene-based materials have been intensively explored as anodes in LICs due to their unique structure and outstanding electrochemical properties and attractive achievements have been made. In this review, the recent progresses of graphene-based anode materials for LICs are systematically summarized. Their synthesis procedure, structure and electrochemical performance are discussed with a special focus on the role of graphene. Finally, the outlook and remaining challenges are presented with some constructive guidelines for future research.
      Citation: Chemistry
      PubDate: 2021-10-14
      DOI: 10.3390/chemistry3040089
      Issue No: Vol. 3, No. 4 (2021)
  • Chemistry, Vol. 3, Pages 1247-1257: A Practical Laboratory-Scale Synthesis
           of All Eight Stereoisomeric Forms of Terpene Linalool Oxide

    • Authors: Stefano Serra, Davide De Simeis, Sara Papili
      First page: 1247
      Abstract: In this work, we describe a user-friendly procedure for the preparation of all the isomeric forms of the terpene linalool oxide. The presented method is based on the transformation of the linalool enantiomers into the corresponding diastereoisomeric mixtures of the two furanoid oxides and two pyranoid oxides. Taking advantage of the different steric hindrance of the hydroxyl functional groups, the pyranoid forms were separated as a diastereoisomeric mixtures of their benzoate esters. Conversely, the cis- and trans-furanoid isomers were transformed in the corresponding acetates, which were directly separated by chromatography. The hydrolysis of the latter esters afforded cis- and trans-furanoid linalool oxides whereas the same reaction performed on the benzoates mixture afforded a separable mixture of cis- and trans-pyranoid linalool oxide. Overall, the method features, as a unique mandatory requirement, the availability of both linalool enantiomers, and can be conveniently performed from a milligram to a multigram scale.
      Citation: Chemistry
      PubDate: 2021-10-16
      DOI: 10.3390/chemistry3040090
      Issue No: Vol. 3, No. 4 (2021)
  • Chemistry, Vol. 3, Pages 1258-1270: Effect of Fiber Content and Silane
           Treatment on the Mechanical Properties of Recycled
           Acrylonitrile-Butadiene-Styrene Fiber Composites

    • Authors: Vardaan Chauhan, Timo Kärki, Juha Varis
      First page: 1258
      Abstract: The aim of the present study was to investigate the effects of fiber content and then silane treatment on the mechanical performance of the natural fiber composites of recycled acrylonitrile–butadiene–styrene (ABS) provided by the automotive sector. Wood and palmyra fibers were used as fillers in 10% and 20% fiber content composites. The fibers were treated with N-(2-Aminoethyl)-3-aminopropyltrimethoxysilane to improve the interfacial adhesion between fibers and polymer matrices. The mechanical properties of the composites were determined by tensile and impact tests. Morphological analysis was later performed using a scanning electron microscope (SEM). According to the experiment results, the tensile and impact strength of both wood and palmyra fibers increase after silane treatment. However, for the low-wood-fiber-content composite, the tensile and impact strength decrease after silane treatment due to the presence of an excess amount of silane relative to fiber content. The addition of wood and palmyra fibers significantly improved the tensile modulus of composite material and further increases slightly after silane treatment. Finally, SEM analysis shows a homogenous mix of fibers and polymer matrices with fewer voids after silane treatment, thereby improving interfacial adhesion.
      Citation: Chemistry
      PubDate: 2021-11-01
      DOI: 10.3390/chemistry3040091
      Issue No: Vol. 3, No. 4 (2021)
  • Chemistry, Vol. 3, Pages 1271-1285: Biogenic Silver Nanoparticles
           Conjugated with Nisin: Improving the Antimicrobial and Antibiofilm
           Properties of Nanomaterials

    • Authors: Patricia Zimet, Ruby Valadez, Sofía Raffaelli, María Belén Estevez, Helena Pardo, Silvana Alborés
      First page: 1271
      Abstract: Microbial technology offers a green alternative for the synthesis of value-added nanomaterials. In particular, fungal compounds can improve silver nanoparticle production, stabilizing colloidal nanoparticles. Based on a previous study by our group, silver nanoparticles obtained using the extracellular cell-free extracts of Phanerochaete chrysosporium (PchNPs) have shown antimicrobial and antibiofilm activity against Gram-negative bacteria. Moreover, nisin—a bacteriocin widely used as a natural food preservative—has recently gained much attention due its antimicrobial action against Gram-positive bacteria in biomedical applications. Therefore, the aim of this work was to conjugate biogenic silver nanoparticles (PchNPs) with nisin to obtain nanoconjugates (PchNPs@nis) with enhanced antimicrobial properties. Characterization assays were conducted to determine physicochemical properties of PchNPs@nis, and also their antibacterial and antibiofilm activities were studied. The formation of PchNPs@nis was confirmed by UV-Vis, TEM, and Raman spectroscopy analysis. Different PchNPs@nis nanobioconjugates showed diameter values in the range of 60–130 nm by DLS and surface charge values between −20 and −13 mV. Nisin showed an excellent affinity to PchNPs, with binding efficiencies higher than 75%. Stable synthesized PchNPs@nis nanobioconjugates were not only able to inhibit biofilm formation by S. aureus, but also showed inhibition of the planktonic cell growth of Staphyloccocus aureus and Escherichia coli, broadening the spectrum of action of the unconjugated antimicrobials against Gram-positive and Gram-negative bacteria. In conclusion, these results show the promising application of PchNPs@nis, prepared via green technology, as potential antimicrobial nanomaterials.
      Citation: Chemistry
      PubDate: 2021-11-04
      DOI: 10.3390/chemistry3040092
      Issue No: Vol. 3, No. 4 (2021)
  • Chemistry, Vol. 3, Pages 1286-1301: Is Aromatic Nitration Spin Density

    • Authors: Amedeo Capobianco, Alessandro Landi, Andrea Peluso
      First page: 1286
      Abstract: The mechanism of aromatic nitration is critically reviewed with particular emphasis on the paradox of the high positional selectivity of substitution in spite of low substrate selectivity. Early quantum chemical computations in the gas phase have suggested that the retention of positional selectivity at encounter-limited rates could be ascribed to the formation of a radical pair via an electron transfer step occurring before the formation of the Wheland intermediate, but calculations which account for the effects of solvent polarization and the presence of counterion do not support that point of view. Here we report a brief survey of the available experimental and theoretical data, adding a few more computations for better clarifying the role of electron transfer for regioselectivity.
      Citation: Chemistry
      PubDate: 2021-11-04
      DOI: 10.3390/chemistry3040093
      Issue No: Vol. 3, No. 4 (2021)
  • Chemistry, Vol. 3, Pages 1302-1313: Are Metallacyclopentadienes Always

    • Authors: Ricardo Casiano-González, José Enrique Barquera-Lozada
      First page: 1302
      Abstract: Even though metallacyclopentadienes (MCPs) are among the most common metallacycles, their electron delocalization (aromaticity) has received far less attention than other metallacycles, such as metallabenzenes. We systematically studied the aromaticity of MCPs with energetic (isomerization stabilization energy), density (delocalization index) and magnetic (current density) aromaticity indices. The indices agree that metallacyclopentadienes are, in general, weakly aromatic at most. The 18e− complexes showed the expected weak aromaticity, and only the d8 molecules are somewhat anti-aromatic. However, the theoretical account of the aromaticity of the 16e− MCPs is more convoluted. We find that the aromatic criteria for a 16e−d4 ruthenacyclopentadiene disagree. The lack of agreement shows that significant electron delocalization is not always related to great stability or to strong diatropic currents.
      Citation: Chemistry
      PubDate: 2021-11-04
      DOI: 10.3390/chemistry3040094
      Issue No: Vol. 3, No. 4 (2021)
  • Chemistry, Vol. 3, Pages 1314-1343: Recent Advances on 2D Materials
           towards 3D Printing

    • Authors: I. Jénnifer Gómez, Nuria Alegret, Antonio Dominguez-Alfaro, Manuel Vázquez Sulleiro
      First page: 1314
      Abstract: In recent years, 2D materials have been implemented in several applications due to their unique and unprecedented properties. Several examples can be named, from the very first, graphene, to transition-metal dichalcogenides (TMDs, e.g., MoS2), two-dimensional inorganic compounds (MXenes), hexagonal boron nitride (h-BN), or black phosphorus (BP). On the other hand, the accessible and low-cost 3D printers and design software converted the 3D printing methods into affordable fabrication tools worldwide. The implementation of this technique for the preparation of new composites based on 2D materials provides an excellent platform for next-generation technologies. This review focuses on the recent advances of 3D printing of the 2D materials family and its applications; the newly created printed materials demonstrated significant advances in sensors, biomedical, and electrical applications.
      Citation: Chemistry
      PubDate: 2021-11-06
      DOI: 10.3390/chemistry3040095
      Issue No: Vol. 3, No. 4 (2021)
  • Chemistry, Vol. 3, Pages 1344-1362: Preparation and Characterization of
           Polyethylene Biocomposites Reinforced by Rice Husk: Application as
           Potential Packaging Material

    • Authors: Emi Govorcin Bajsic, Ana Persic, Tomislav Jemric, Josip Buhin, Dajana Kucic Grgic, Emilija Zdraveva, Krunoslav Zizek, Tamara Holjevac Grguric
      First page: 1344
      Abstract: The development of biodegradable materials as food packaging material is important not only due to the reduction in environmental pollution but also because of an improvement in the functionality. Rice husk-reinforced biopolymers have offered a possible solution to waste-disposal problems associated with traditional petroleum-derived plastics. Rice husk-reinforced low density polyethylene (LDPE)-based biocomposites have been of great interest for their use as food packaging material. In this work, the LDPE/RH biocomposites with different rice husk (RH) content (10, 20, 30, 40 and 50 wt.%) were prepared by the melt mixing process in a laboratory Brabender mixer. The effect of RH content on the physical, thermal and mechanical properties of LDPE was investigated. More importantly, this work aimed to research the biodegradation of the LDPE/RH biocomposites as well as their effect on ‘Granny Smith’ apples’ respiration. The results showed that the incorporation of RH into the LDPE decreased the thermal stability of LDPE, increased water vapour permeability and water absorption, and increased the degree of crystallinity. The incorporation of RH increased the biodegradability of LDPE as well as the postharvest quality of ‘Granny Smith’ apples. The addition of RH in LDPE film significantly decreased fruit respiration and increased firmness as compared to LDPE film. The composting results showed that after the LDPE/RH biocomposite films were biodegraded for 21 days, the biocomposite films with the highest content of rice husks were the most degraded.
      Citation: Chemistry
      PubDate: 2021-11-10
      DOI: 10.3390/chemistry3040096
      Issue No: Vol. 3, No. 4 (2021)
  • Chemistry, Vol. 3, Pages 1363-1370: On the Aromaticity and 13C-NMR Pattern
           of Pentagonal-Pyramidal Hexamethylbenzene Dication [C6(CH3)6]2+: A
           {C5(CH3)5}−–{CCH3}3+ Aggregate

    • Authors: Desmond MacLeod-Carey, Alvaro Muñoz-Castro
      First page: 1363
      Abstract: The experimentally characterized hexamethylbenzene dication C6(CH3)62+ shows a pentagonal-pyramidal structure involving a carbon-capped five-membered ring. The structural characterization of this hypercoordination (or hypervalency) gives rise if the aromatic behavior remains in the resulting pentagon ring. Here, we investigated the induced magnetic field of C6(CH3)62+ to gain a deeper understanding of the resulting non-classical structural situation in a representative pentagonal-pyramidal structure. Our results support the view of a C5(CH3)5−/CCH33+ structure, depicting a π-aromatic pentamethylcyclopentadienyl anion with a 6π-electron kernel, with a capped carbon which does not decrease the characteristic shielding cone property of the aromatic ring. Hence, carbon-capped rings are suggested to retain the aromatic behavior from the former aromatic ring. We expect that the analysis of both the overall magnetic response and NMR chemical shifts may be informative to unravel the characteristic patterns in the formation of hypervalent carbon atoms involving non-classical chemical environments.
      Citation: Chemistry
      PubDate: 2021-11-11
      DOI: 10.3390/chemistry3040097
      Issue No: Vol. 3, No. 4 (2021)
  • Chemistry, Vol. 3, Pages 1371-1380: Investigation of SiO2 Nanoparticle
           Retention in Flow Channels, Its Remediation Using Surfactants and
           Relevance of Artificial Intelligence in the Future

    • Authors: Sushant Bajpai, Nehil Shreyash, Muskan Sonker, Saurabh Kr Tiwary, Susham Biswas
      First page: 1371
      Abstract: In this study, the effect of these variables on commercial silica NP retention was presented in a fabricated flow model considering only the physical adsorption aspects of silica NP retention. From our observations, it was established that while silica NP concentration, flow rate and salt are key variables in influencing silica NP agglomeration and retention, the effect of temperature was highly subdued. The effect of salt-induced agglomeration was particularly severe at moderate salinity (≈4 wt% NaCl). To mitigate the effect of salt-induced agglomeration, a commonly used anionic surfactant, sodium dodecyl sulfate (SDS) was added to the solution and the silica NP retention was tabulated. An amount of 0.3 wt% SDS was found to negate salt-induced agglomeration significantly, paving the way for use of silica NP solutions, even in the presence of saline conditions. A section on the prospective use of artificial intelligence for this purpose has been included. This study is useful for understanding NP retention behaviour, especially in the presence of salinity and its mitigation using surfactants, in flow applications.
      Citation: Chemistry
      PubDate: 2021-11-12
      DOI: 10.3390/chemistry3040098
      Issue No: Vol. 3, No. 4 (2021)
  • Chemistry, Vol. 3, Pages 1381-1391: The Magnetic Response of Starphenes

    • Authors: Mesías Orozco-Ic, Gabriel Merino
      First page: 1381
      Abstract: The aromaticity of [n]starphenes (n = 1, 4, 7, 10, 13, 16), as well as starphene-based [19]dendriphene, is addressed by calculating the magnetically induced current density and the induced magnetic field, using the pseudo-π model. When an external magnetic field is applied, these systems create diatropic currents that split into a global peripheral current surrounding the starphene skeleton and several local currents in the acene-based arms, resulting in large shielding cones above the arms. In particular, the arm currents are smaller than their linear analogs, and in general, the strengths of the ring currents tend to weaken as the starphene get larger.
      Citation: Chemistry
      PubDate: 2021-11-20
      DOI: 10.3390/chemistry3040099
      Issue No: Vol. 3, No. 4 (2021)
  • Chemistry, Vol. 3, Pages 1392-1400: Degradation of Polypropylene and Jute
           Fiber-Reinforced Composites Exposed to Natural and Accelerated Aging:
           Mechanical Properties and Wettability

    • Authors: Paula Bertolino Sanvezzo, Fernanda Pereira de Castro Negreiros, Marcia Cristina Branciforti
      First page: 1392
      Abstract: Population growth and the way resources are being exploited are directly affecting the environment. The natural fiber market, for example, is worth billions of dollars and a huge amount of the fibers becomes waste. This considerable amount of waste motivates the study of the fibers as a reinforcement in polymeric matrix, which benefits both the environmental sustainability and technical-commercial development of new materials with good properties and reduced cost. In this study, jute fiber-reinforced composites previously manufactured from an industrial waste (W), polypropylene, compatibilizer, and nano-calcium carbonate (N), were exposed to natural and accelerated aging. The composites were tested by infrared spectroscopy, contact angle (CA) measurement, and tensile test. Infrared analysis showed greater oxidative degradation after accelerated aging. All CA values continued above 90° after natural aging. Among all compositions, the ones with the presence of N had the highest CA values, showing that N acted as a waterproofing agent. After accelerated aging, a significant decrease in all CA values was observed. The composites did not show significant variation in the elastic modulus after either aging. Deformation at break decreased significantly for compositions with no jute fiber in both aging programs. No remarkable reduction was observed in the compositions with jute fibers.
      Citation: Chemistry
      PubDate: 2021-11-23
      DOI: 10.3390/chemistry3040100
      Issue No: Vol. 3, No. 4 (2021)
  • Chemistry, Vol. 3, Pages 1401-1410: On-Surface Synthesis of Boroxine-Based

    • Authors: Elia Turco, Matus Stredansky, Roberto Costantini, Javier A. Martinez, Martina Dell’Angela, Elena Zerbato, Daniele Toffoli, Giovanna Fronzoni, Alberto Morgante, Luca Floreano, Albano Cossaro
      First page: 1401
      Abstract: The on-surface synthesis of boroxine-containing molecules can be a convenient method of introducing specific functionalities. Here, we show the validity of a previously described synthesis protocol on the Au (111) surface by applying it to a different molecular precursor. We study in detail the assembly of the precursor, highlighting possible intermediate stages of the condensation process. We combine scanning tunneling microscopy and X-ray spectroscopies to fully characterize both the morphology and the electronic properties of the system. DFT calculations are presented to assign the main electronic transitions originating the B K-edge absorption spectrum. The study paves the way to a facile strategy for functionalizing a surface with molecules of tailored sizes and compositions.
      Citation: Chemistry
      PubDate: 2021-11-30
      DOI: 10.3390/chemistry3040101
      Issue No: Vol. 3, No. 4 (2021)
  • Chemistry, Vol. 3, Pages 1411-1436: Aromaticity of Heterocirculenes

    • Authors: Nataliya N. Karaush-Karmazin, Glib V. Baryshnikov, Boris F. Minaev
      First page: 1411
      Abstract: This review summarizes the results on the aromaticity of a series of synthesized and hypothetical neutral heterocirculene molecules and their double charged ions. The aromaticity of heterocirculenes is a direct reflection of their electronic structure responsible for the specific optoelectronic and photophysical properties. We show how the presence of a heteroatom in the outer macrocycle affects the aromaticity of hetero[8]circulenes. In addition, we also describe the change in aromaticity and strain energy for a series of the “lower” (n < 8) and “higher” (n > 8) hetero[n]circulenes. It was demonstrated that the loss of planarity with increased strain leads to an increased antiaromaticity of the lower hetero[n]circulenes, whereas higher hetero[n]circulenes demonstrate a more pronounced aromatic nature because of the small departure from planarity of each heteroarene ring in hetero[n]circulene molecule. Finally, we discuss the aromatic nature of the first examples of π-extended hetero[8]circulenes.
      Citation: Chemistry
      PubDate: 2021-12-03
      DOI: 10.3390/chemistry3040102
      Issue No: Vol. 3, No. 4 (2021)
  • Chemistry, Vol. 3, Pages 1437-1463: Occurrence of Marine Ingredients in
           Fragrance: Update on the State of Knowledge

    • Authors: Nacera Riad, Mohamed Reda Zahi, Naima Bouzidi, Yasmina Daghbouche, Ouassila Touafek, Mohamed El Hattab
      First page: 1437
      Abstract: The fragrance field of perfumes has attracted considerable scientific, industrial, cultural, and civilizational interest. The marine odor is characterized by the specific smell of sea breeze, seashore, algae, and oyster, among others. Marine odor is a more recent fragrance and is considered as one of the green and modern fragrances. The smells reproducing the marine environment are described due to their content of Calone 1951 (7-methyl-2H-1,5-benzodioxepin-3(4H)-one), which is a synthetic compound. In addition to the synthetic group of benzodioxepanes, such as Calone 51 and its derivatives, three other groups of chemical compounds seem to represent the marine smell. The first group includes the polyunsaturated cyclic ((+)-Dictyopterene A) and acyclic (giffordene) hydrocarbons, acting as pheromones. The second group corresponds to polyunsaturated aldehydes, such as the (Z,Z)-3,6-nonadienal, (E,Z)-2,6-nonadienal, which are most likely derived from the degradation of polyunsaturated fatty acids. The third group is represented by small molecules such as sulfur compounds and halogenated phenols which are regarded as the main flavor compounds of many types of seafood. This review exposes, most notably, the knowledge state on the occurrence of marine ingredients in fragrance. We also provide a detailed discussion on several aspects of essential oils, which are the most natural ingredients from various marine sources used in fragrance and cosmetics, including synthetic and natural marine ingredients.
      Citation: Chemistry
      PubDate: 2021-12-04
      DOI: 10.3390/chemistry3040103
      Issue No: Vol. 3, No. 4 (2021)
  • Chemistry, Vol. 3, Pages 1464-1480: Fully Biobased Reactive Extrusion of
           Biocomposites Based on PLA Blends and Hazelnut Shell Powders (HSP)

    • Authors: Luca Panariello, Maria-Beatrice Coltelli, Alessandro Vannozzi, Daniele Bonacchi, Laura Aliotta, Andrea Lazzeri
      First page: 1464
      Abstract: The production of biocomposites based on natural fiber waste and biopolymers is constantly increasing because of their renewability, biodegradability, and the accordance with the circular economy principles. The aim of this work is to contrast the disadvantages in the production of biocomposites, such as reduction of molecular weight through the use of biobased chain extenders. For this purpose, epoxidized soybean oil (ESO) and dicarboxylic acids (DCAs) were used to contrast the slight chain scission observed in a poly(lactic acid) (PLA)/poly(butylene succinate-co-adipate) (PBSA) binary blend caused by the melt mixing with hazelnut shell powder (HSP). Two different dimensions of HSPs were considered in this study as well as different concentrations of the ESO/DCA system, comparing succinic acid and malic acid as dicarboxylic acids. Melt viscosity parameters, such as torque and melt volume rate (MVR), were measured to investigate the chain extender effect during the extrusion. In addition, the reactivity of the ESO/DCA system was investigated through infrared spectroscopy. The effect of chain extenders on thermal properties, in particular on the crystallinity of PLA, and on mechanical properties of final biocomposites was investigated to understand their potentialities in industrial application. Results of this study evidenced a modest increase in melt viscosity due to ESO/malic acid chain extension system, but only for the HSP with the lower dimension (so the higher surface area) and adding 0.5 wt.% of ESO/malic acid. Thus, the slight chain scission of polyesters, not significantly affecting the final properties of these biocomposites, is the most relevant effect that was revealed in this complex reactive system.
      Citation: Chemistry
      PubDate: 2021-12-05
      DOI: 10.3390/chemistry3040104
      Issue No: Vol. 3, No. 4 (2021)
  • Chemistry, Vol. 3, Pages 687-703: Investigation into the Re-Arrangement of
           Copper Foams Pre- and Post-CO2 Electrocatalysis

    • Authors: Jennifer A. Rudd, Sandra Hernandez-Aldave, Ewa Kazimierska, Louise B. Hamdy, Odin J. E. Bain, Andrew R. Barron, Enrico Andreoli
      First page: 687
      Abstract: The utilization of carbon dioxide is a major incentive for the growing field of carbon capture. Carbon dioxide could be an abundant building block to generate higher-value chemical products. Herein, we fabricated a porous copper electrode capable of catalyzing the reduction of carbon dioxide into higher-value products, such as ethylene, ethanol and propanol. We investigated the formation of the foams under different conditions, not only analyzing their morphological and crystal structure, but also documenting their performance as a catalyst. In particular, we studied the response of the foams to CO2 electrolysis, including the effect of urea as a potential additive to enhance CO2 catalysis. Before electrolysis, the pristine and urea-modified foam copper electrodes consisted of a mixture of cuboctahedra and dendrites. After 35 min of electrolysis, the cuboctahedra and dendrites underwent structural rearrangement affecting catalysis performance. We found that alterations in the morphology, crystallinity and surface composition of the catalyst were conducive to the deactivation of the copper foams.
      Citation: Chemistry
      PubDate: 2021-06-28
      DOI: 10.3390/chemistry3030048
      Issue No: Vol. 3, No. 3 (2021)
  • Chemistry, Vol. 3, Pages 704-713: Experimental and Computational Studies
           on N-alkylation Reaction of N-Benzoyl 5-(Aminomethyl)Tetrazole

    • Authors: Younas Aouine, Aaziz Jmiai, Anouar Alami, Abdallah El Asri, Souad El Issami, Idriss Bakas
      First page: 704
      Abstract: The N-alkylation reaction of N-benzoyl 5-(aminomethyl)tetrazole (5-AMT) with benzyl bromide was carried out in the presence of K2CO3 as a base. Two separable regioisomers were obtained, thus their purification led to determine the proportion of each of them, and their structures were attributed essentially based on 1H and 13C NMR spectroscopy in addition to the elemental analysis and MS data. In order to confirm the results obtained at the synthesis level, a computational study was carried out by application of density functional theory (DFT) using the Becke three-parameter hybrid exchange functional and the Lee-Yang-Parr correlation functional (B3LYP).
      Citation: Chemistry
      PubDate: 2021-07-05
      DOI: 10.3390/chemistry3030049
      Issue No: Vol. 3, No. 3 (2021)
  • Chemistry, Vol. 3, Pages 714-727: Microwave-Assisted Synthesis, Optical
           and Theoretical Characterization of Novel
           2-(imidazo[1,5-a]pyridine-1-yl)pyridinium Salts

    • Authors: Luca M. Cavinato, Giorgio Volpi, Elisa Fresta, Claudio Garino, Andrea Fin, Claudia Barolo
      First page: 714
      Abstract: In the last few years, imidazo[1,5-a]pyridine scaffolds and derivatives have attracted growing attention due to their unique chemical structure and optical behaviors. In this work, a series of pyridylimidazo[1,5-a]pyridine derivatives and their corresponding pyridinium salts were synthesized and their optical properties investigated to evaluate the effect of the quaternization on the optical features both in solution and polymeric matrix. A critical analysis based on the spectroscopic data, chemical structures along with density functional theory calculation is reported to address the best strategies to prevent aggregation and optimize the photophysical properties. The obtained results describe the relationship between chemical structure and optical behaviors, highlighting the role of pendant pyridine. Finally, the presence of a positive charge is fundamental to avoid any possible aggregation process in polymeric films.
      Citation: Chemistry
      PubDate: 2021-07-06
      DOI: 10.3390/chemistry3030050
      Issue No: Vol. 3, No. 3 (2021)
  • Chemistry, Vol. 3, Pages 728-733: Electrochemical Switching of
           First-Generation Donor-Acceptor Stenhouse Adducts (DASAs): An Alternative
           Stimulus for Triene Cyclisation

    • Authors: Nicholas D. Shepherd, Harrison S. Moore, Jonathon E. Beves, Deanna M. D’Alessandro
      First page: 728
      Abstract: Donor-acceptor Stenhouse adducts (DASAs) are a photo-switch class that undergoes triene cyclisation in response to visible light. Herein, electrochemical oxidation is demonstrated as an effective alternative stimulus for the triene cyclisation commonly associated with photo-switching.
      Citation: Chemistry
      PubDate: 2021-07-07
      DOI: 10.3390/chemistry3030051
      Issue No: Vol. 3, No. 3 (2021)
  • Chemistry, Vol. 3, Pages 734-743: Novel Ansa-Chain Conformation of a
           Semi-Synthetic Rifamycin Prepared Employing the Alder-Ene Reaction:
           Crystal Structure and Absolute Stereochemistry

    • Authors: Christopher S. Frampton, James H. Gall, David D. MacNicol
      First page: 734
      Abstract: Rifamycins are an extremely important class of antibacterial agents whose action results from the inhibition of DNA-dependent RNA synthesis. A special arrangement of unsubstituted hydroxy groups at C21 and C23, with oxygen atoms at C1 and C8 is essential for activity. Moreover, it is known that the antibacterial action of rifamycin is lost if either of the two former hydroxy groups undergo substitution and are no longer free to act in enzyme inhibition. In the present work, we describe the successful use of an Alder-Ene reaction between Rifamycin O, 1 and diethyl azodicarboxylate, yielding 2, which was a targeted introduction of a relatively bulky group close to C21 to protect its hydroxy group. Many related azo diesters were found to react analogously, giving one predominant product in each case. To determine unambiguously the stereochemistry of the Alder-Ene addition process, a crystalline zwitterionic derivative 3 of the diethyl azodicarboxylate adduct 2 was prepared by reductive amination at its spirocyclic centre C4. The adduct, as a mono chloroform solvate, crystallized in the non-centrosymmetric Sohnke orthorhombic space group, P212121. The unique conformation and absolute stereochemistry of 3 revealed through X-ray crystal structure analysis is described.
      Citation: Chemistry
      PubDate: 2021-07-11
      DOI: 10.3390/chemistry3030052
      Issue No: Vol. 3, No. 3 (2021)
  • Chemistry, Vol. 3, Pages 744-752: Light-Induced Charge Accumulation in
           PTCDI/Pentacene/Ag(111) Heterojunctions

    • Authors: Roberto Costantini, Albano Cossaro, Alberto Morgante, Martina Dell’Angela
      First page: 744
      Abstract: The incorporation of singlet fission (SF) chromophores in solar cells is expected to bring significant increases in the power conversion efficiency thanks to multiexciton generation. However, efficient charge generation in the device is determined by the energy level alignment (ELA) between the active materials, which should favor exciton transport and separation under illumination. By combining ultraviolet photoemission spectroscopy and optical differential reflectance measurements, we determine the ELA in a prototypical SF heterojunction between pentacene (Pc) and perylene-tetracarboxylic-diimide (PTCDI) grown on Ag(111). Time-resolved X-ray photoelectron spectroscopy on such a system reveals light-induced modifications of the ELA; by measuring the transient shift of the core level photoemission lines we observe an accumulation of long-lived holes in the PTCDI within the first hundred picoseconds after the optical pump.
      Citation: Chemistry
      PubDate: 2021-07-13
      DOI: 10.3390/chemistry3030053
      Issue No: Vol. 3, No. 3 (2021)
  • Chemistry, Vol. 3, Pages 753-764: Substrate–Solvent Crosstalk—Effects
           on Reaction Kinetics and Product Selectivity in Olefin Oxidation Catalysis

    • Authors: Rita N. Sales, Samantha K. Callear, Pedro D. Vaz, Carla D. Nunes
      First page: 753
      Abstract: In this work, we explored how solvents can affect olefin oxidation reactions catalyzed by MCM-bpy-Mo catalysts and whether their control can be made with those players. The results of this study demonstrated that polar and apolar aprotic solvents modulated the reactions in different ways. Experimental data showed that acetonitrile (aprotic polar) could largely hinder the reaction rate, whereas toluene (aprotic apolar) did not. In both cases, product selectivity at isoconversion was not affected. Further insights were obtained by means of neutron diffraction experiments, which confirmed the kinetic data and allowed for the proposal of a model based on substrate–solvent crosstalk by means of hydrogen bonding. In addition, the model was also validated in the ring-opening reaction (overoxidation) of styrene oxide to benzaldehyde, which progressed when toluene was the solvent (reaching 31% styrene oxide conversion) but was strongly hindered when acetonitrile was used instead (reaching only 7% conversion) due to the establishment of H-bonds in the latter. Although this model was confirmed and validated for olefin oxidation reactions, it can be envisaged that it may also be applied to other catalytic reaction systems where reaction control is critical, thereby widening its use.
      Citation: Chemistry
      PubDate: 2021-07-19
      DOI: 10.3390/chemistry3030054
      Issue No: Vol. 3, No. 3 (2021)
  • Chemistry, Vol. 3, Pages 765-782: Singlet/Triplet State Anti/Aromaticity
           of CyclopentadienylCation: Sensitivity to Substituent Effect

    • Authors: Milovan Stojanović, Jovana Aleksić, Marija Baranac-Stojanović
      First page: 765
      Abstract: It is well known that singlet state aromaticity is quite insensitive to substituent effects, in the case of monosubstitution. In this work, we use density functional theory (DFT) calculations to examine the sensitivity of triplet state aromaticity to substituent effects. For this purpose, we chose the singlet state antiaromatic cyclopentadienyl cation, antiaromaticity of which reverses to triplet state aromaticity, conforming to Baird’s rule. The extent of (anti)aromaticity was evaluated by using structural (HOMA), magnetic (NICS), energetic (ISE), and electronic (EDDBp) criteria. We find that the extent of triplet state aromaticity of monosubstituted cyclopentadienyl cations is weaker than the singlet state aromaticity of benzene and is, thus, slightly more sensitive to substituent effects. As an addition to the existing literature data, we also discuss substituent effects on singlet state antiaromaticity of cyclopentadienyl cation.
      Citation: Chemistry
      PubDate: 2021-07-21
      DOI: 10.3390/chemistry3030055
      Issue No: Vol. 3, No. 3 (2021)
  • Chemistry, Vol. 3, Pages 783-799: A New Supported Manganese-Based
           Coordination Complex as a Nano-Catalyst for the Synthesis of
           Indazolophthalazinetriones and Investigation of Its Antibacterial Activity

    • Authors: Maryam Ariannezhad, Davood Habibi, Somayyeh Heydari, Vahideh Khorramabadi
      First page: 783
      Abstract: A new magnetic supported manganese-based coordination complex (Fe3O4@SiO2@CPTMS@MBOL@ Mn) was prepared in consecutive stages and characterized via various techniques (VSM, SEM, TEM, XRD, FT-IR, EDX, TG-DTA, and ICP). To evaluate its application, it was used for synthesis of divers Indazolophthalazinetriones in a simple procedure via the one-pot three-component condensation reaction of aldehydes, dimedone, and phthalhydrazide in ethanol under reflux conditions. The Mn catalyst can be recycled without any noticeable loss in catalytic activity. Additionally, the antibacterial properties of the nano-catalyst were studied against some bacterial strains.
      Citation: Chemistry
      PubDate: 2021-07-22
      DOI: 10.3390/chemistry3030056
      Issue No: Vol. 3, No. 3 (2021)
  • Chemistry, Vol. 3, Pages 800-817: Carbon Monoxide Therapy Using Hybrid
           Carbon Monoxide-Releasing/Nrf2-Inducing Molecules through a
           Neuroprotective Lens

    • Authors: Flavia Cavicchioli, Izzy M. Cesarotti, Madison Fangman, Josh Lua, Raymond Hautamaki, Sylvain Doré
      First page: 800
      Abstract: Carbon monoxide (CO) has long been known for its toxicity. However, in recent decades, new applications for CO as a therapeutic compound have been proposed, and multiple forms of CO therapy have since been developed and studied. Previous research has found that CO has a role as a gasotransmitter and promotes anti-inflammatory and antioxidant effects, making it an avenue of interest for medicine. Such effects are possible because of the Nrf2/HO1 pathway, which has become a target for therapy development because its activation also leads to CO release. Currently, different forms of treatment involving CO include inhaled CO (iCO), carbon monoxide-releasing molecules (CORMs), and hybrid carbon monoxide-releasing molecules (HYCOs). In this article, we review the progression of CO studies to develop possible therapies, the possible mechanisms involved in the effects of CO, and the current forms of therapy using CO.
      Citation: Chemistry
      PubDate: 2021-07-23
      DOI: 10.3390/chemistry3030057
      Issue No: Vol. 3, No. 3 (2021)
  • Chemistry, Vol. 3, Pages 818-820: Memorial Issue Dedicated to Dr. Howard
           D. Flack: The Man behind the Flack Parameter

    • Authors: Catherine E. Housecroft, Katharina M. Fromm
      First page: 818
      Abstract: This Special Issue of Chemistry is dedicated to Dr. Howard D. Flack (1943–2017), a renowned crystallographer who transformed the way in which, by using single crystal X-ray diffraction, we are able to determine the absolute structure of a crystalline material, and thereby determine the absolute configuration of molecular species within the material [...]
      Citation: Chemistry
      PubDate: 2021-07-27
      DOI: 10.3390/chemistry3030058
      Issue No: Vol. 3, No. 3 (2021)
  • Chemistry, Vol. 3, Pages 821-830: Oxidation of Terpenoids to Achieve
           High-Value Flavor and Fragrances—Questioning Microalgae Oxidative
           Capabilities in the Biotransformation of the Sesquiterpene Valencene and
           of Selected Natural Apocarotenoids

    • Authors: Davide De Simeis, Stefano Serra, Alessandro Di Fonzo, Francesco Secundo
      First page: 821
      Abstract: Natural flavor and fragrance market size is expected to grow steadily due to the rising consumer demand of natural ingredients. This market request is guided by the general opinion that the production of natural compounds leads to a reduction of pollution, with inherent advantages for the environment and people’s health. The biotransformation reactions have gained high relevance in the production of natural products. In this context, few pieces of research have described the role of microalgae in the oxidation of terpenoids. In this present study, we questioned the role of microalgal based oxidation in the synthesis of high-value flavors and fragrances. This study investigated the role of three different microalgae strains, Chlorella sp. (211.8b and 211.8p) and Chlorococcum sp. (JB3), in the oxidation of different terpenoid substrates: α-ionone, β-ionone, theaspirane and valencene. Unfortunately, the experimental data showed that the microalgal strains used are not responsible for the substrate oxidation. In fact, our experiments demonstrate that the transformation of the four starting compounds is a photochemical reaction that involves the oxygen as oxidant. Even though these findings cast a shadow on the use of these microorganisms for an industrial purpose, they open a new possible strategy to easily obtain nootkatone in a natural way by just using an aqueous medium, oxygen and light.
      Citation: Chemistry
      PubDate: 2021-07-28
      DOI: 10.3390/chemistry3030059
      Issue No: Vol. 3, No. 3 (2021)
  • Chemistry, Vol. 3, Pages 831-833: Coordination Polymers and Metal-Organic
           Frameworks: Structures and Applications—A Themed Issue in Honor of
           Professor Christoph Janiak on the Occasion of His 60th Birthday

    • Authors: Catherine E. Housecroft
      First page: 831
      Abstract: This themed issue of Chemistry is in honor of Professor Christoph Janiak on the occasion of his 60th birthday, and celebrates his innovative contributions to the fields of supramolecular chemistry, coordination polymers, networks and metal-organic frameworks, inorganic/organic hybrid materials and inorganic materials from ionic liquids [...]
      Citation: Chemistry
      PubDate: 2021-07-28
      DOI: 10.3390/chemistry3030060
      Issue No: Vol. 3, No. 3 (2021)
  • Chemistry, Vol. 3, Pages 834-853: Unveiling the Intramolecular Ionic
           Diels–Alder Reactions within Molecular Electron Density Theory

    • Authors: Luis R. Domingo, Mar Ríos-Gutiérrez, María José Aurell
      First page: 834
      Abstract: The intramolecular ionic Diels–Alder (IIDA) reactions of two dieniminiums were studied within the Molecular Electron Density Theory (MEDT) at the ωB97XD/6-311G(d,p) computational level. Topological analysis of the electron localization function (ELF) of dieniminiums showed that their electronic structures can been seen as the sum of those of butadiene and ethaniminium. The superelectrophilic character of dieniminiums accounts for the high intramolecular global electron density transfer taking place from the diene framework to the iminium one at the transition state structures (TSs) of these IIDA reactions, which are classified as the forward electro density flux. The activation enthalpy associated with the IIDA reaction of the experimental dieniminium, 8.7 kcal·mol−1, was closer to that of the ionic Diels–Alder (I-DA) reaction between butadiene and ethaniminium, 9.3 kcal·mol−1. However, the activation Gibbs free energy of the IIDA reaction was 12.7 kcal·mol−1 lower than that of the intermolecular I-DA reaction. The strong exergonic character of the IIDA reaction, higher than 20.5 kcal·mol−1, makes the reaction irreversible. These IIDA reactions present a total re/exo and si/endo diastereoselectivity, which is controlled by the most favorable chair conformation of the tetramethylene chain. ELF topological analysis of the single bond formation indicated that these IIDA reactions take place through a non-concerted two-stage one-step mechanism. Finally, ELF and atoms-in-molecules (AIM) topological analyses of the TS associated with the inter and intramolecular processes showed the great similarity between them.
      Citation: Chemistry
      PubDate: 2021-08-03
      DOI: 10.3390/chemistry3030061
      Issue No: Vol. 3, No. 3 (2021)
  • Chemistry, Vol. 3, Pages 854-860: Isolation and Antimalarial Activity of a
           New Flavonol from Tithonia diversifolia Leaf Extract

    • Authors: Talkmore Ngarivhume, Anwar Noreljaleel, Susanna L. Bonnet, Anke Wilhelm
      First page: 854
      Abstract: An antiplasmodial activity-guided isolation was carried out on the dichloromethane extract of Tithonia diversifolia dried leaves. A total of five germacranolide type sesquiterpene lactones and a new flavonol, 3,6-dihydroxy-2-(4′-hydroxyphenyl)-7-methoxy-4H-chromen-4-one, were isolated. The flavonol reported an IC50 above 6.00 µM against the chloroquine sensitive strain, NF54. The antimalarial activity of the Tithonia diversifolia dichloromethane leaf extract was attributed to orizabin and tagitinin C.
      Citation: Chemistry
      PubDate: 2021-08-12
      DOI: 10.3390/chemistry3030062
      Issue No: Vol. 3, No. 3 (2021)
  • Chemistry, Vol. 3, Pages 861-872: Magnetic Shielding Study of Bonding and
           Aromaticity in Corannulene and Coronene

    • Authors: Peter B. Karadakov
      First page: 861
      Abstract: Bonding and aromaticity in the bowl-shaped C5v and planar D5h geometries of corannulene and the planar D6h geometry of coronene are investigated using 3D isosurfaces and 2D contour plots of the isotropic magnetic shielding σiso(r) and, for planar geometries, of the out-of-plane component of the shielding tensor σzz(r). Corannulene and coronene both feature conjoined shielded “doughnuts” around a peripheral six-membered carbon ring, suggesting strong bonding interactions and aromatic stability; a deshielded region inside the hub ring of corannulene indicates that this ring is antiaromatic, more so in planar corannulene. The switch from the planar to the bowl-shaped geometry of corannulene is shown to enhance both bonding and the local aromaticities of the five- and six-membered rings; these factors, in addition to ring strain reduction, favour the bowl-shaped geometry. The most and least shielded bonds in both corannulene and coronene turn out to be the spoke and hub bonds, respectively. The higher π electron activity over spoke bonds in planar corannulene and coronene is supported by σzz(r) contour plots in planes 1 Å above the respective molecular planes; these findings about spoke bonds are somewhat unexpected, given that ring current studies indicate next to no currents over spoke bonds.
      Citation: Chemistry
      PubDate: 2021-08-12
      DOI: 10.3390/chemistry3030063
      Issue No: Vol. 3, No. 3 (2021)
  • Chemistry, Vol. 3, Pages 873-888: Chemical Functionalization of Graphene
           Nanoplatelets with Hydroxyl, Amino, and Carboxylic Terminal Groups

    • Authors: Cheng Peng, Xiaoyan Zhang
      First page: 873
      Abstract: As the most studied two-dimensional material, graphene is still attracting a lot of attention from both academia and industry due to its fantastic properties such as lightness, excellent mechanical strength, and high conductivity of heat and electricity. As an important branch of graphene materials, graphene nanoplatelets show numerous applications such as in coating, fillers of polymer composites, energy conversion and storage devices, sensing, etc. Chemical functionalization can introduce different functional groups to graphene nanoplatelets and can potentially endow them with different properties and functions to meet the increasing demand in the fields mentioned above. In this minireview, we present an overview of the research progress of functionalized graphene nanoplatelets bearing hydroxyl, amino, and carboxylic terminal groups, including both covalent and noncovalent approaches. These terminal groups allow subsequent functionalization reactions to attach additional moieties. Relevant characterization techniques, different applications, challenges, and future directions of functionalized graphene nanoplatelets are also critically summarized.
      Citation: Chemistry
      PubDate: 2021-08-23
      DOI: 10.3390/chemistry3030064
      Issue No: Vol. 3, No. 3 (2021)
  • Chemistry, Vol. 3, Pages 889-895: Ultrasonic Dyeing of Polyester Fabric
           with Azo Disperse Dyes Clubbed with Pyridonones and Its UV Protection

    • Authors: Alya M. Al-Etaibi, Morsy Ahmed El-Apasery
      First page: 889
      Abstract: The textile sector is closely linked to environmental pollution as a result of the use of toxic chemicals and their disposal in liquid waste, which negatively affects for the environment. Moreover, textile industries, especially wet processing, consume a large amount of energy, water, and chemical auxiliaries. Therefore, there is an urgent need to find a solution that takes the problem of environmental pollution into account. Considering ultrasound as an environmentally safe alternative for dyeing polyester fabrics with the disperse dyes that we have prepared before, the comparison between the ultrasonic dyeing method and conventional dyeing at low temperatures was investigated. Dye exhaustion on polyester fabrics and fastness properties such as the washing, rubbing, light, and perspiration of all of the dyed fabrics were performed by two dyeing methods. Additionally, the ultraviolet protection factors (UPF) for dyed polyester fabrics were evaluated.
      Citation: Chemistry
      PubDate: 2021-08-24
      DOI: 10.3390/chemistry3030065
      Issue No: Vol. 3, No. 3 (2021)
  • Chemistry, Vol. 3, Pages 896-915: Dispersion of Micro Fibrillated
           Cellulose (MFC) in Poly(lactic acid) (PLA) from Lab-Scale to

    • Authors: Giovanna Molinari, Vito Gigante, Stefano Fiori, Laura Aliotta, Andrea Lazzeri
      First page: 896
      Abstract: In the present study, two commercial typologies of microfibrillated cellulose (MFC) (Exilva and Celish) with 2% wt % were firstly melt-compounded at the laboratory scale into polylactic acid (PLA) by a microcompounder. To reach an MFC proper dispersion and avoid the well-known aglomeration problems, the use of two kinds of biobased plasticisers (poly(ethylene glycol) (PEG) and lactic acid oligomer (OLA)) were investigated. The plasticizers had the dual effect of dispersing the MFC, and at the same time, they counterbalanced the excessive stiffness caused by the addition of MFC to the PLA matrix. Several preliminaries dilution tests, with different aqueous cellulose suspension/plasticizer weight ratios were carried out. These tests were accompanied by SEM observations and IR and mechanical tests on compression-molded films in order to select the best plasticizer content. The best formulation was then scaled up in a semi-industrial twin-screw extruder, feeding the solution by a peristaltic pump, to optimize the industrial-scale production of commercial MFC-based composites with a solvent-free method. From this study, it can be seen that the use of plasticisers as dispersing aids is a biobased and green solution that can be easily used in conventional extrusion techniques.
      Citation: Chemistry
      PubDate: 2021-08-25
      DOI: 10.3390/chemistry3030066
      Issue No: Vol. 3, No. 3 (2021)
  • Chemistry, Vol. 3, Pages 916-934: Topological Analysis of Magnetically
           Induced Current Densities in Strong Magnetic Fields Using Stagnation

    • Authors: Tom J. P. Irons, Adam Garner, Andrew M. Teale
      First page: 916
      Abstract: Stagnation graphs provide a useful tool to analyze the main topological features of the often complicated vector field associated with magnetically induced currents. Previously, these graphs have been constructed using response quantities appropriate for modest applied magnetic fields. We present an implementation capable of producing these graphs in arbitrarily strong magnetic fields, using current-density-functional theory. This enables us to study how the topology of the current vector field changes with the strength and orientation of the applied magnetic field. Applications to CH4, C2H2 and C2H4 are presented. In each case, we consider molecular geometries optimized in the presence of the magnetic field. The stagnation graphs reveal subtle changes to this vector field where the symmetry of the molecule remains constant. However, when the electronic state and symmetry of the corresponding equilibrium geometry changes with increasing field strength, the changes to the stagnation graph are extensive. We expect that the approach presented here will be helpful in interpreting changes in molecular structure and bonding in the strong-field regime.
      Citation: Chemistry
      PubDate: 2021-08-26
      DOI: 10.3390/chemistry3030067
      Issue No: Vol. 3, No. 3 (2021)
  • Chemistry, Vol. 3, Pages 935-958: Synthesis and Self-Assembling Properties
           of Peracetylated β-1-Triazolyl Alkyl D-Glucosides and D-Galactosides

    • Authors: Pooja Sharma, Anji Chen, Dan Wang, Guijun Wang
      First page: 935
      Abstract: Carbohydrate-based low-molecular-weight gelators (LMWGs) are useful classes of compounds due to their numerous applications. Among sugar-based LMWGs, certain peracetylated sugar beta-triazole derivatives were found to be effective organogelators and showed interesting self-assembling properties. To further understand the structural influence towards molecular assemblies and obtain new functional materials with interesting properties, we designed and synthesized a library of tetraacetyl beta-1-triazolyl alkyl-D-glucosides and D-galactosides, in which a two or three carbon spacer is inserted between the anomeric position and the triazole moiety. A series of 16 glucose derivatives and 14 galactose derivatives were synthesized and analyzed. The self-assembling properties of these new triazole containing glycoconjugates in different solvents were analyzed. Several glucose derivatives were found to be effective LMWGs, with compound 7a forming gels in a variety of organic solvents as well as in the presence of metal ions in aqueous solutions. The organogels formed by several compounds were characterized using optical microscopy, atomic force microscopy (AFM) and UV-vis spectroscopy, etc. The co-gels formed by compound 7a with the Fmoc derivative 7i showed interesting fluorescence enhancement upon gelation. Several gelators were also characterized using powder X-ray diffraction and FT-IR spectroscopy. The potential applications of these sugar-based gelators for drug delivery and dye removal were also studied.
      Citation: Chemistry
      PubDate: 2021-08-28
      DOI: 10.3390/chemistry3030068
      Issue No: Vol. 3, No. 3 (2021)
  • Chemistry, Vol. 3, Pages 959-978: Questions in the Chemical Enzymology of

    • Authors: Rona R. Ramsay, Alen Albreht
      First page: 959
      Abstract: We have structure, a wealth of kinetic data, thousands of chemical ligands and clinical information for the effects of a range of drugs on monoamine oxidase activity in vivo. We have comparative information from various species and mutations on kinetics and effects of inhibition. Nevertheless, there are what seem like simple questions still to be answered. This article presents a brief summary of existing experimental evidence the background and poses questions that remain intriguing for chemists and biochemists researching the chemical enzymology of and drug design for monoamine oxidases (FAD-containing EC
      Citation: Chemistry
      PubDate: 2021-08-31
      DOI: 10.3390/chemistry3030069
      Issue No: Vol. 3, No. 3 (2021)
  • Chemistry, Vol. 3, Pages 979-990: Phytochemicals from Rhizophora mucronata
           Propagules, Its In Vitro Anti-Cancer and In Silico Drug-Likeness Potential

    • Authors: Nurhanan Murni Yunos, Sui Kiong Ling, Asiah Osman, Zunoliza Abdullah, Nor Jannah Sallehudin
      First page: 979
      Abstract: This is the first report to identify the presence of 3-O-caffeoyl quinic acid (1), 4-O-caffeoyl quinic acid (2), 5-O-caffeoyl quinic acid (3), epi-catechin (4), and procyanidin B2 (5) in the young propagules of Rhizophora mucronata. Compounds 2–5 were purified and then treated against breast, colorectal, and ovarian cancer cell lines for 72 h and the results of the Sulphorhodomine-B (SRB) assay were evaluated for percent cell viability and IC50 values. Epi-catechin, 4-O-caffeoyl quinic acid, 5-O-caffeoyl quinic acid and procyanidin B2 showed strong to moderate inhibitory effects when treated on breast (T47D), colorectal (HT29), and ovarian (A2780, SKOV3) cancer cell lines with IC50 values ranging from 16.77 ± 0.58 to 28.28 ± 0.89 μg/mL. In silico evaluation was performed to evaluate the drug-likeness and toxicological effects of these compounds using Molinspiration calculation and OSIRIS program. It was found that compounds 2, 3, and 4 have the potential to be orally active and have a low risk in exerting the mutagenic, tumorigenic, irritant, and reproductive effects.
      Citation: Chemistry
      PubDate: 2021-09-02
      DOI: 10.3390/chemistry3030070
      Issue No: Vol. 3, No. 3 (2021)
  • Chemistry, Vol. 3, Pages 991-1004: Magnetic Aromaticity of Cycloporphyrin

    • Authors: Alessandro Landi, Francesco Ferdinando Summa, Guglielmo Monaco
      First page: 991
      Abstract: The ascertainment of magnetic aromaticity is not necessarily straightforward, especially for large and bent systems, such as the cycloporphyrin nanorings recently synthesized by the group of Anderson. Six of these cycloporphyrin nanorings were studied here computationally. Indirect methods, based on nuclear shielding and magnetizabilities, and direct methods, based on standard quantum mechanics, were both used effectively to determine their magnetically induced current strength, which mostly confirmed Anderson’s classification. However, in the case of hexanions, and in particular for cyclohexaporphyrin hexacations, a significant cancellation of delocalized diatropic and paratropic flow occurred, showing that the resultant faint aromatic character was a result of competing aromatic and antiaromatic contributions, as also evidenced by the ipsocentric method. A warning is renewed on the use of isotropic shielding to determine the tropicity of the magnetically induced current.
      Citation: Chemistry
      PubDate: 2021-09-02
      DOI: 10.3390/chemistry3030071
      Issue No: Vol. 3, No. 3 (2021)
  • Chemistry, Vol. 3, Pages 1005-1021: Spatial Contributions to 1H NMR
           Chemical Shifts of Free-Base Porphyrinoids

    • Authors: Heike Fliegl, Maria Dimitrova, Raphael J. F. Berger, Dage Sundholm
      First page: 1005
      Abstract: A recently developed methodology for calculating, analyzing, and visualizing nuclear magnetic shielding densities is used for studying spatial contributions including ring-current contributions to 1H nuclear magnetic resonance (NMR) chemical shifts of aromatic and anti-aromatic free-base porphyrinoids. Our approach allows a visual inspection of the spatial origin of the positive (shielding) and negative (deshielding) contributions to the nuclear magnetic shielding constants. Diatropic and paratropic current-density fluxes yield both shielding and deshielding contributions implying that not merely the tropicity of the current density determines whether the contribution has a shielding or deshielding character. Instead the shielding or deshielding contribution is determined by the direction of the current-density flux with respect to the studied nucleus.
      Citation: Chemistry
      PubDate: 2021-09-05
      DOI: 10.3390/chemistry3030072
      Issue No: Vol. 3, No. 3 (2021)
  • Chemistry, Vol. 3, Pages 1022-1036: Electronic Currents and Anapolar
           Response Induced in Molecules by Monochromatic Light

    • Authors: Francesco Ferdinando Summa, Paolo Lazzeretti
      First page: 1022
      Abstract: It is shown that the electric dipole- and electric quadrupole–anapole polarizabilities, denoted respectively by fαβ′ and gα,βγ′, and the anapole magnetizability aαβ, are intrinsic properties of the electron cloud of molecules responding to optical fields. fαβ′ is a nonvanishing property of chiral and achiral compounds, whereas aαβ is suitable for enantiomer discrimination of chiral species. They can conveniently be evaluated by numerical integration, employing a formulation complementary to that provided by perturbation theory and relying on the preliminary computation of electronic current density tensors all over the molecular domain. The origin dependence of the dynamic anapolar response is rationalized via related computational techniques employing numerical integration, as well as definitions of molecular property tensors, for example, electric dipole and electric quadrupole polarizabilties and magnetizability. A preliminary application of the theory is reported for the Ra enantiomer of the hydrogen peroxide molecule, evaluating tensor components of electric dipole-anapole polarizability and anapole magnetizability as functions of the dihedral angle ϕ≡∠ H-O-O-H in the range 0∘≤ϕ≤180∘.
      Citation: Chemistry
      PubDate: 2021-09-05
      DOI: 10.3390/chemistry3030073
      Issue No: Vol. 3, No. 3 (2021)
  • Chemistry, Vol. 3, Pages 1037-1046: Yb to Tb Cooperative Upconversion in
           Supramolecularly Assembled Complexes in a Solution

    • Authors: Lohona K. Soro, Cyrille Charpentier, Frédéric Przybilla, Yves Mély, Aline M. Nonat, Loïc J. Charbonnière
      First page: 1037
      Abstract: The podand-type ligand L, based on a tertiary amine substituted by three pyridyl-6-phosphonic acid functions, forms hydrated complexes with Ln3+ cations. The luminescence properties of the YbL complex were studied in D2O as a function of the pD and temperature. In basic conditions, increases in the luminescence quantum yield and the excited state lifetime of the Yb centered emission associated with the 2F5/2 → 2F7/2 transition were observed and attributed to a change in the hydration number from two water molecules in the first coordination sphere of Yb at acidic pH to a single one in basic conditions. Upon the addition of TbCl3 salts to a solution containing the YbL complex in D2O, heteropolynuclear Yb/Tb species formed, and excitation of the Yb at 980 nm resulted in the observation of the typical visible emission of Tb as a result of a cooperative upconversion (UC) photosensitization process. The UC was further evidenced by the quadratic dependence of the UC emission as a function of the laser power density.
      Citation: Chemistry
      PubDate: 2021-09-06
      DOI: 10.3390/chemistry3030074
      Issue No: Vol. 3, No. 3 (2021)
  • Chemistry, Vol. 3, Pages 1047-1056: The Non-Anhydrous, Minimally Basic
           Synthesis of the Dopamine D2 Agonist [18F]MCL-524

    • Authors: James A. H. Inkster, Anna W. Sromek, Vamsidhar Akurathi, John L. Neumeyer, Alan B. Packard
      First page: 1047
      Abstract: The dopamine D2 agonist MCL-524 is selective for the D2 receptor in the high-affinity state (D2high), and, therefore, the PET analogue, [18F]MCL-524, may facilitate the elucidation of the role of D2high in disorders such as schizophrenia. However, the previously reported synthesis of [18F]MCL-524 proved difficult to replicate and was lacking experimental details. We therefore developed a new synthesis of [18F]MCL-524 using a “non-anhydrous, minimally basic” (NAMB) approach. In this method, [18F]F− is eluted from a small (10–12 mg) trap-and-release column with tetraethylammonium tosylate (2.37 mg) in 7:3 MeCN:H2O (0.1 mL), rather than the basic carbonate or bicarbonate solution that is most often used for [18F]F− recovery. The tosylated precursor (1 mg) in 0.9 mL anhydrous acetonitrile was added directly to the eluate, without azeotropic drying, and the solution was heated (150 °C/15 min). The catechol was then deprotected with the Lewis acid In(OTf)3 (10 equiv.; 150 °C/20 min). In contrast to deprotection with protic acids, Lewis-acid-based deprotection facilitated the efficient removal of byproducts by HPLC and eliminated the need for SPE extraction prior to HPLC purification. Using the NAMB approach, [18F]MCL-524 was obtained in 5–9% RCY (decay-corrected, n = 3), confirming the utility of this improved method for the multistep synthesis of [18F]MCL-524 and suggesting that it may applicable to the synthesis of other 18F-labeled radiotracers.
      Citation: Chemistry
      PubDate: 2021-09-09
      DOI: 10.3390/chemistry3030075
      Issue No: Vol. 3, No. 3 (2021)
  • Chemistry, Vol. 3, Pages 1057-1062: Spectroscopic Evidence of New
           Low-Dimensional Planar Carbon Allotropes Based on Biphenylene via
           On-Surface Ullmann Coupling

    • Authors: Teng Zhang, Cesare Grazioli, Huixia Yang, Kaiyue Jiang, Iulia Emilia Brumboiu, Liangguang Jia, Liwei Liu, Carla Puglia, Xiaodong Zhuang, Yeliang Wang
      First page: 1057
      Abstract: The bottom-up synthesis and preliminary characterizations of a new biphenylene-based 2D framework are presented. This new low-dimensional carbon allotrope potentially completes the many hypothesized carbon networks based on biphenylene.
      Citation: Chemistry
      PubDate: 2021-09-13
      DOI: 10.3390/chemistry3030076
      Issue No: Vol. 3, No. 3 (2021)
  • Chemistry, Vol. 3, Pages 1063-1073: The B2 Structural Motif as a Tool for
           Modulating Ring Currents in Monocyclic Li Clusters

    • Authors: Slađana Đorđević, Slavko Radenković
      First page: 1063
      Abstract: Magnetically induced current densities, calculated at the M06-2X/def2-TZVP level using the diamagnetic-zero version of the continuous transformation of origin of current density (CTOCD-DZ) method, were employed to study the aromaticity in Li3B2− and Li4B2. It was found that the Li3/Li4 rings in Li3B2− and Li4B2 remarkably resemble the monocyclic Li3+ and Li42+ clusters. Unlike the parent Li3+ and Li42+ systems that sustain negligibly weak global current density circulation, the Li3B2− and Li4B2 clusters exhibit a strong diatropic current density. The present work demonstrates how structural modifications introduced by the B2 unit can be used for modulating the current density in cyclic Li-based clusters.
      Citation: Chemistry
      PubDate: 2021-09-14
      DOI: 10.3390/chemistry3030077
      Issue No: Vol. 3, No. 3 (2021)
  • Chemistry, Vol. 3, Pages 1074-1088: Absorption and Isomerization of
           Azobenzene Guest Molecules in Polymeric Nanoporous Crystalline Phases

    • Authors: Nicola Coscia, Antonietta Cozzolino, Manohar Golla, Paola Rizzo
      First page: 1074
      Abstract: PPO co-crystalline (CC) films including azobenzene guest molecules have been prepared and characterized by WAXD, FTIR and UV-Visible measurements. Isomerization reactions of azobenzene (photo-induced trans to cis and spontaneous cis to trans) included in α and β nanoporous-crystalline (NC) phases leading to CC phases, or simply absorbed in amorphous phase have been studied on thick and thin films. Spectroscopic analysis shows that photo-isomerization of azobenzene occurs without expulsion of azobenzene guest molecules from crystalline phases. Sorption studies of α and β NC films immersed into photo-isomerized azobenzene solution reveal a higher selectivity of the β NC phase toward cis azobenzene isomer than the α NC phase, inducing us to propose the β NC phase as particularly suitable for absorbing spherically bulky guest molecules.
      Citation: Chemistry
      PubDate: 2021-09-16
      DOI: 10.3390/chemistry3030078
      Issue No: Vol. 3, No. 3 (2021)
  • Chemistry, Vol. 3, Pages 1089-1100: Chirality Transfer in a
           Calixarene-Based Directional Pseudorotaxane Complex

    • Authors: Gerardo Concilio, Carmine Gaeta, Paolo Della Sala, Veronica Iuliano, Carmen Talotta, Guglielmo Monaco, Stefano Superchi, Sandra Belviso, Placido Neri
      First page: 1089
      Abstract: Hexamethoxycalix[6]arene 3 forms a directional pseudorotaxane complex with the chiral axle (S)-(α-methyl-benzyl)benzylammonium 2+. Between the two (endo-chiral)-2+@3 and (exo-chiral)-2+@3 pseudorotaxane stereoisomers, the former is preferentially formed. This result confirms the validity of the “endo-α-methyl-benzyl rule”, previously reported by us. DFT calculations suggest that C-H … π interactions between the methyl group of 2+ and the calixarene aromatic rings, determine the stereoselectivity of the threading process toward the “endo-α-methyl-benzyl preference”. An amplification of optical rotation is observed upon formation of the pseudorotaxane complex (endo-chiral)-2+@3 with respect to free axle 2+. Thus, the specifical rotation of the 1:1 mixture of chiral 2+·B(ArF)4− salt and achiral 3 was augmented upon formation of the pseudorotaxane and DFT calculations were used to rationalize this result.
      Citation: Chemistry
      PubDate: 2021-09-18
      DOI: 10.3390/chemistry3030079
      Issue No: Vol. 3, No. 3 (2021)
  • Chemistry, Vol. 3, Pages 444-453: Chloropentaphenyldisiloxane—Model
           Study on Intermolecular Interactions in the Crystal Structure of a
           Monofunctionalized Disiloxane

    • Authors: Jonathan O. Bauer, Tobias Götz
      First page: 444
      Abstract: Small functional siloxane units have gained great interest as molecular model systems for mimicking more complex silicate structures both in nature and in materials chemistry. The crystal structure of chloropentaphenyldisiloxane, which was synthesized for the first time, was elucidated by single-crystal X-ray diffraction analysis. The molecular crystal packing was studied in detail using state-of-the-art Hirshfeld surface analysis together with a two-dimensional fingerprint mapping of the intermolecular interactions. It was found that the phenyl C–H bonds act as donors for both weak C–H···π and C–H···Cl hydrogen bond interactions. The influence of intramolecular Si–O–Si bond parameters on the acceptor capability of functional groups in intermolecular hydrogen bond interactions is discussed.
      Citation: Chemistry
      PubDate: 2021-03-29
      DOI: 10.3390/chemistry3020033
      Issue No: Vol. 3, No. 2 (2021)
  • Chemistry, Vol. 3, Pages 454-508: Polyprotic Acids and Beyond—An
           Algebraic Approach

    • Authors: Harald Kalka
      First page: 454
      Abstract: For an N-protic acid–base system, the set of nonlinear equations (i.e., mass action and balance laws) provides a simple analytical solution/formula for any integer N ≥ 1. The approach is applicable for the general case of zwitterionic acids HNA+Z (e.g., amino acids, NTA, and EDTA), which includes (i) the “ordinary acids” as a special case (Z = 0) and (ii) surface complexation. Examples are presented for N = 1 to 6. The high-N perspective allows classification of equivalence points (including isoionic and isoelectric points). Principally, there are two main approaches to N-protic acids: one from hydrochemistry and one “outside inorganic hydrochemistry”. They differ in many ways: the choice of the reference state (either HNA or A−N), the reaction type (dissociation or association), the type/nature of the acidity constants, and the structure of the formulas. Once the (nonlinear) conversion between the two approaches is established, we obtain a systematics of acidity constants (macroscopic, microscopic, cumulative, and Simms). Finally, from the viewpoint of statistical mechanics (canonical isothermal–isobaric ensemble), buffer capacities, buffer intensities, and higher pH derivatives are actually fluctuations in the form of variance, skewness, and kurtosis.
      Citation: Chemistry
      PubDate: 2021-04-07
      DOI: 10.3390/chemistry3020034
      Issue No: Vol. 3, No. 2 (2021)
  • Chemistry, Vol. 3, Pages 509-510: Supramolecular Chemistry in the 3rd

    • Authors: Catherine E. Housecroft
      First page: 509
      Abstract: The description of supramolecular chemistry as “chemistry beyond the molecule” (Jean-Marie Lehn, 1987 Nobel Lecture and Gautam R [...]
      Citation: Chemistry
      PubDate: 2021-04-08
      DOI: 10.3390/chemistry3020035
      Issue No: Vol. 3, No. 2 (2021)
  • Chemistry, Vol. 3, Pages 511-524: Molecular Docking and Molecular Dynamics
           Simulation Studies of Quinoline-3-Carboxamide Derivatives with DDR
           Kinases–Selectivity Studies towards ATM Kinase

    • Authors: Srimadhavi Ravi, Bhanu Priya, Pankaj Dubey, Vijay Thiruvenkatam, Sivapriya Kirubakaran
      First page: 511
      Abstract: Quinoline-3-carboxamides are an essential class of drug-like small molecules that are known to inhibit the phosphatidylinositol 3-kinase-related kinases (PIKK) family kinases. The quinoline nitrogen is shown to bind to the hinge region of the kinases, making them competitive inhibitors of adenosine triphosphate (ATP). We have previously designed and synthesized quinoline-3-carboxamides as potential ataxia telangiectasia mutated (ATM) kinase inhibitors to function as an adjuvant treatment with DNA damaging agents. This article discusses the molecular docking studies performed with these derivatives with the DNA damage and response (DDR) kinases-ATM, ataxia telangiectasia and rad3 related (ATR), and DNA dependent protein kinase catalytic subunit (DNA-PKcs) and highlights their selectivity towards ATM kinase. Docking studies were also performed with mTOR and PI3Kγ, which are close homologs of the DDR kinases. Molecular dynamics simulations were performed for one of the inhibitors against all the enzymes to establish the stability of the interactions involved. Finally, the absorption, distribution, metabolism, and excretion (ADME) properties of the inhibitors were predicted using the QikProp manual in Maestro. In conclusion, the molecules synthesized showed high selectivity towards the ATM kinase in comparison with the other kinases, though the sequence similarity between them was relatively high.
      Citation: Chemistry
      PubDate: 2021-04-11
      DOI: 10.3390/chemistry3020036
      Issue No: Vol. 3, No. 2 (2021)
  • Chemistry, Vol. 3, Pages 525-531: The Impact of Structural Defects on
           Iodine Adsorption in UiO-66

    • Authors: John Maddock, Xinchen Kang, Lifei Liu, Buxing Han, Sihai Yang, Martin Schröder
      First page: 525
      Abstract: Radioactive I2 (iodine) produced as a by-product of nuclear fission poses a risk to public health if released into the environment, and it is thus vital to develop materials that can capture I2 vapour. Materials designed for the capture and storage of I2 must have a high uptake capacity and be stable for long-term storage due the long half-life of 129I. UiO-66 is a highly stable and readily tuneable metal-organic framework (MOF) into which defect sites can be introduced. Here, a defective form of UiO-66 (UiO-66-FA) was synthesised and the presence of missing cluster moieties confirmed using confocal fluorescence microscopy and gas sorption measurements. The uptake of I2 vapour in UiO-66-FA was measured using thermal gravimetric analysis coupled mass spectrometry (TGA-MS) to be 2.25 g g−1, almost twice that (1.17 g g−1) of the pristine UiO-66. This study will inspire the design of new efficient I2 stores based upon MOFs incorporating structural defects.
      Citation: Chemistry
      PubDate: 2021-04-12
      DOI: 10.3390/chemistry3020037
      Issue No: Vol. 3, No. 2 (2021)
  • Chemistry, Vol. 3, Pages 532-549: Exploitation of Baird Aromaticity and
           Clar’s Rule for Tuning the Triplet Energies of Polycyclic Aromatic

    • Authors: Felix Plasser
      First page: 532
      Abstract: Polycyclic aromatic hydrocarbons (PAH) are a prominent substance class with a variety of applications in molecular materials science. Their electronic properties crucially depend on the bond topology in ways that are often highly non-intuitive. Here, we study, using density functional theory, the triplet states of four biphenylene-derived PAHs finding dramatically different triplet excitation energies for closely related isomeric structures. These differences are rationalised using a qualitative description of Clar sextets and Baird quartets, quantified in terms of nucleus independent chemical shifts, and represented graphically through a recently developed method for visualising chemical shielding tensors (VIST). The results are further interpreted in terms of a 2D rigid rotor model of aromaticity and through an analysis of the natural transition orbitals involved in the triplet excited states showing good consistency between the different viewpoints. We believe that this work constitutes an important step in consolidating these varying viewpoints of electronically excited states.
      Citation: Chemistry
      PubDate: 2021-04-14
      DOI: 10.3390/chemistry3020038
      Issue No: Vol. 3, No. 2 (2021)
  • Chemistry, Vol. 3, Pages 550-577: Carbohydrate-Based Azacrown Ethers in
           Asymmetric Syntheses

    • Authors: István Orbán, Péter Bakó, Zsolt Rapi
      First page: 550
      Abstract: Carbohydrate-based crown ethers represent a special group of chiral phase transfer catalysts. Several derivatives of these macrocycles have been synthesized in our research group. Among these compounds, monoaza-15-crown-5 lariat ethers proved to be effective phase transfer and enantioselective catalysts in certain reactions. Those chiral azacrown ethers incorporating various carbohydrate moieties in the macrocyclic structure are reviewed, which generated asymmetric induction in reactions, such as Michael addition, epoxidation of enones, Darzens condensation and Michael-initiated ring-closure (MIRC) reaction. Effects on the catalytic activity of the structural changes are the focus.
      Citation: Chemistry
      PubDate: 2021-04-15
      DOI: 10.3390/chemistry3020039
      Issue No: Vol. 3, No. 2 (2021)
  • Chemistry, Vol. 3, Pages 578-584: Absolute Configuration of In Situ
           Crystallized (+)-γ-Decalactone

    • Authors: Michael Patzer, Nils Nöthling, Richard Goddard, Christian W. Lehmann
      First page: 578
      Abstract: Knowledge about the absolute configuration of small bioactive organic molecules is essential in pharmaceutical research because enantiomers can exhibit considerably different effects on living organisms. X-ray crystallography enables chemists to determine the absolute configuration of an enantiopure compound due to anomalous dispersion. Here, we present the determination of the absolute configuration of the flavoring agent (+)-γ-decalactone, which is liquid under ambient conditions. Single crystals were grown from the liquid in a glass capillary by in situ cryo-crystallization. Diffraction data collection was performed using Cu-Kα radiation. The absolute configuration was confirmed. The molecule consists of a linear aliphatic non-polar backbone and a polar lactone head. In the solid state, layers of polar and non-polar sections of the molecule alternating along the c-axis of the unit cell are observed. In favorable cases, this method of absolute configuration determination of pure liquid (bioactive) agents or liquid products from asymmetric catalysis is a convenient alternative to conventional methods of absolute structure determination, such as optical rotatory dispersion, vibrational circular dichroism, ultraviolet-visible spectroscopy, use of chiral shift reagents in proton NMR and Coulomb explosion imaging.
      Citation: Chemistry
      PubDate: 2021-04-21
      DOI: 10.3390/chemistry3020040
      Issue No: Vol. 3, No. 2 (2021)
  • Chemistry, Vol. 3, Pages 585-597: Solid Phase Nitrosylation of
           Enantiomeric Cobalt(II) Complexes

    • Authors: Mads Sondrup Møller, Morten Czochara Liljedahl, Vickie McKee, Christine J. McKenzie
      First page: 585
      Abstract: Accompanied by a change in color from red to black, the enantiomorphic phases of the cobalt complexes of a chiral salen ligand (L2−, Co(L)·CS2, and Co(L) (L = LS,S or LR,R)) chemisorb NO (g) at atmospheric pressure and rt over hours for the CS2 solvated phase, and within seconds for the desolvated phase. NO is installed as an axial nitrosyl ligand. Aligned but unconnected voids in the CS2 desorbed Co(LR,R)·CS2 structure indicate conduits for the directional desorption of CS2 and reversible sorption of NO, which occur without loss of crystallinity. Vibrational circular dichroism (VCD) spectra have been recorded for both hands of LH2, Zn(L), Co(L)·CS2, Co(L), Co(NO)(L), and Co(NO)(L)·CS2, revealing significant differences between the solution-state and solid-state spectra. Chiral induction enables the detection of the νNO band in both condensed states, and surprisingly also the achiral lattice solvent (CS2 (νCS at 1514 cm−1)) in the solid-state VCD. Solution-state spectra of the paramagnetic Co(II) complex shows a nearly 10-fold enhancement and more extensive inversion of polarity of the vibrations of dominant VCD bands compared to the spectra of the diamagnetic compounds. This enhancement is less pronounced when there are fewer polarity inversions in the solid state VCD spectra.
      Citation: Chemistry
      PubDate: 2021-04-28
      DOI: 10.3390/chemistry3020041
      Issue No: Vol. 3, No. 2 (2021)
  • Chemistry, Vol. 3, Pages 598-611: Erdmann’s Anion—An Inexpensive and
           Useful Species for the Crystallization of Illicit Drugs after Street

    • Authors: Matthew R. Wood, Sandra Mikhael, Ivan Bernal, Roger A. Lalancette
      First page: 598
      Abstract: Erdmann’s anion [1,6-diammino tetranitrocobaltate(III)] is useful in the isolation and crystallization of recently confiscated street drugs needing to be identified and catalogued. The protonated form of such drugs forms excellent crystals with that anion; moreover, Erdmann’s salts are considerably less expensive than the classically used AuCl4− anion to isolate them, while preparation of high-quality crystals is equally easy in both cases. We describe the preparation and structures of the K+CoH6N6O8− and NH4+CoH6N7O8−, salts of Erdmann’s. In addition, herein are described the preparations of this anion’s salts with cocaine (C17H28CoN7O12), with methamphetamine (C10H22CoN7O8), and with methylone (C22H34CoN8O14), whose preparation and stereochemistry had been characterized by the old AuCl4− salts methodology. For all species in this report, the space groups and cell constants were determined at 296 and 100 K, looking for possible thermally induced polymorphism—none was found. Since the structures were essentially identical at the two temperatures studied, we discuss only the 100 K results. Complete spheres of data accessible to a Bruker ApexII diffractometer with Cu–Kα radiation, λ = 1.54178 Å, were recorded and used in the refinements. Using the refined single crystal structural data for the street drugs, we computed their X-ray powder diffraction patterns, which are beneficial as quick identification standards in law enforcement work.
      Citation: Chemistry
      PubDate: 2021-04-30
      DOI: 10.3390/chemistry3020042
      Issue No: Vol. 3, No. 2 (2021)
  • Chemistry, Vol. 3, Pages 612-629: Assessment of Computational Tools for
           Predicting Supramolecular Synthons

    • Authors: Bhupinder Sandhu, Ann McLean, Abhijeet S. Sinha, John Desper, Christer B. Aakerӧy
      First page: 612
      Abstract: The ability to predict the most likely supramolecular synthons in a crystalline solid is a valuable starting point for subsequently predicting the full crystal structure of a molecule with multiple competing molecular recognition sites. Energy and informatics-based prediction models based on molecular electrostatic potentials (MEPs), hydrogen-bond energies (HBE), hydrogen-bond propensity (HBP), and hydrogen-bond coordination (HBC) were applied to the crystal structures of twelve pyrazole-based molecules. HBE, the most successful method, correctly predicted 100% of the experimentally observed primary intermolecular-interactions, followed by HBP (87.5%), and HBC = MEPs (62.5%). A further HBC analysis suggested a risk of synthon crossover and synthon polymorphism in molecules with multiple binding sites. These easy-to-use models (based on just 2-D chemical structure) can offer a valuable risk assessment of potential formulation challenges.
      Citation: Chemistry
      PubDate: 2021-05-03
      DOI: 10.3390/chemistry3020043
      Issue No: Vol. 3, No. 2 (2021)
  • Chemistry, Vol. 3, Pages 630-646: Catalytic Converters for Vehicle
           Exhaust: Fundamental Aspects and Technology Overview for Newcomers to the

    • Authors: Emmy Kritsanaviparkporn, Francisco M. Baena-Moreno, T. R. Reina
      First page: 630
      Abstract: This works aims to provide an understanding on basic chemical kinetics pertaining to three-way catalytic (TWC) converters from an educational perspective, aimed at those novel readers in this field. Rate of reactions and its factors are explained, showcasing that the chosen catalyst is the main factor affecting the overall rate of reaction. Furthermore, this overview revisit insights of the catalytic converter structure and the environmental issues that come along with it. Lastly, the chemical and physical properties of the reactants and products-pollutant and less-toxic gases—are discussed, in order to gather a better understanding of the reactants and products that enters a catalytic converter.
      Citation: Chemistry
      PubDate: 2021-05-20
      DOI: 10.3390/chemistry3020044
      Issue No: Vol. 3, No. 2 (2021)
  • Chemistry, Vol. 3, Pages 647-657: Two Types of PPARγ Ligands Identified
           in the Extract of Artemisia campestris

    • Authors: Tokio Hasegawa, Mayo Osaka, Yusaku Miyamae, Katsutoshi Nishino, Hiroko Isoda, Kiyokazu Kawada, Mohamed Neffati, Kazuhiro Irie, Masaya Nagao
      First page: 647
      Abstract: The 70% ethanol extract of Artemisia campestris was screened to find PPARγ ligands using the PPARγ ligand-responsive chimera luciferase reporter system. Capillartemisin B was identified as a PPARγ ligand that stimulated lipid accumulation in 3T3-L1 cells. By further purification of PPARγ ligands from a large-scale preparation of the methanol extract of Artemisia campestris, we isolated and identified eupatilin and santaflavone as PPARγ ligands. Weak PPARγ ligand activity of eupatilin or santaflavone in reporter assay was enhanced by a PPARγ antagonist, GW9662, suggesting that santaflavone or eupatilin and GW9662 bound simultaneously to the multiple sub-pockets of the PPARγ ligand-binding domain (LBD) and cooperatively activated PPARγ. Docking simulation suggested that eupatilin binds to the Ω-pocket but not to the AF-2 pocket of Y-shaped PPARγ LBD where artepillin C that differs from capillartemisin B at the C-5′ position without hydroxy group binds. Eupatilin or santaflavone with or without GW9662 did not stimulate lipid accumulation in differentiated 3T3-L1 cells, suggesting that binding of each compound alone or with GW9662 to the Ω-pocket which stimulated the PPARγ-responsive reporter expression was not enough to stimulate lipid accumulation. The PPARγ ligands found in this study have a potential to design the fragment-based drug design of a novel PPARγ ligand that cover the Y-shaped PPARγ LBD.
      Citation: Chemistry
      PubDate: 2021-05-23
      DOI: 10.3390/chemistry3020045
      Issue No: Vol. 3, No. 2 (2021)
  • Chemistry, Vol. 3, Pages 658-671: Study of the Performance of Particles
           Based on Modified Starches Containing Potassium Sorbate and Incorporated
           into Biodegradable Films: Physicochemical Characterization and
           Antimicrobial Action

    • Authors: Paola Alzate, Lía Gerschenson, Silvia Flores
      First page: 658
      Abstract: Ultrasound technique was used to produce native and acetylated cassava starch particles containing potassium sorbate (KS). In order to obtain an active packaging, films with addition of native starch particles containing KS (NKSPF) or added with acetylated starch particles containing KS (AKSPF) were formulated. As control systems, films without KS (CF) or added with KS that was not retained in particles (KSF), were produced. The NKSPF and AKSPF microstructure was consistent with composite materials. Tensile test revealed that CF and KSF were ductile and extensible (stress at break (σb) 2.8–2.5 MPa and strain at break (εb) 284–206%), while NKSPF and AKSPF were more resistant films with higher Young’s Modulus (148–477 MPa) and σb (3.6–17 MPa) but lower εb (40–11%). Moreover, NKSPF and AKSPF developed lower Yellowness Index (6.6–6.5) but higher opacity (19–23%) and solubility in water (31–35%) than KSF (9, 10.8% and 9%, respectively). It was observed that KSF and NKSPF moderately reduced the Zygosaccharomyces bailii growth while AKSPF showed the highest yeast inhibition, three Log-cycles, compared to CF. Additionally, FTIR spectroscopy revealed intensified interactions between KS and modified starch. It was concluded that starch sonication and acetylation were useful modifications to produce particles carrier of KS that improved the physical and antimicrobial performance of active films.
      Citation: Chemistry
      PubDate: 2021-05-27
      DOI: 10.3390/chemistry3020046
      Issue No: Vol. 3, No. 2 (2021)
  • Chemistry, Vol. 3, Pages 672-686: Preparation and Antimicrobial Properties
           of Alginate and Serum Albumin/Glutaraldehyde Hydrogels Impregnated with
           Silver(I) Ions

    • Authors: Louise Gallagher, Alanna Smith, Kevin Kavanagh, Michael Devereux, John Colleran, Carmel Breslin, Karl Richards, Malachy McCann, A. Rooney
      First page: 672
      Abstract: Calcium alginate (CaALG) hydrogel beads and two sets of composite beads, formed from a combination of calcium alginate/propylene glycol alginate/human serum albumin (CaALG/PGA/HSA) and from calcium alginate with the quaternary ammonium salt, (3-(trimethoxysilyl)propyl)-octadecyldimethylammonium chloride (QA), (CaALG/QA), were prepared. Bovine serum albumin (BSA) was condensed with glutaraldehyde (GLA) to form a BSA/GLA hydrogel. The corresponding Ag+-containing gels of all of the above hydrogels were also formed, and slow leaching of the biocidal transition metal ion from the gels bestowed broad spectrum antimicrobial activity. In the absence of added Ag+, CaALG/QA was the only material to deliver marginal to moderate antibacterial and antifungal effects. The Ag+ impregnated hydrogel systems have the potential to maintain the antimicrobial properties of silver, minimising the risk of toxicity, and act as reservoirs to afford ongoing sterility.
      Citation: Chemistry
      PubDate: 2021-06-14
      DOI: 10.3390/chemistry3020047
      Issue No: Vol. 3, No. 2 (2021)
  • Chemistry, Vol. 3, Pages 45-73: Monofluorophosphates—New Examples and a
           Survey of the PO3F2− Anion

    • Authors: Matthias Weil
      First page: 45
      Abstract: During a systematic study of monofluorophosphates, i.e., compounds comprising the tetrahedral anion PO3F2−, twelve, for the most part new, compounds were obtained from aqueous solutions. Crystal structure refinements based on single crystal X-ray diffraction data revealed the previously unknown crystal structures of CdPO3F(H2O)2, Cr2(PO3F)3(H2O)18.8, Pb2(PO3F)Cl2(H2O), (NH4)2M(PO3F)2(H2O)2 (M = Mg, Mn, Co), NH4Cr(PO3F)2(H2O)6, NH4Cu2(H3O2)(PO3F)2, (NH4)2Zn(PO3F)2(H2O)0.2, and (NH4)2Zn3(PO3F)4(H2O), as well as redeterminations of ZnPO3F(H2O)2.5 and (NH4)2Ni(PO3F)2(H2O)6. From the previously unknown crystal structures, CdPO3F(H2O)2 (space group P1¯), Cr2(PO3F)3(H2O)18.8 (P1¯), Pb2(PO3F)Cl2(H2O) (Pnma), NH4Cr(PO3F)2(H2O)6 (R3¯m), (NH4)2Zn(PO3F)2(H2O)0.2 (C2/c), and (NH4)2Zn3(PO3F)4(H2O) (I4¯3d) each crystallizes in an unique crystal structure, whereas compounds (NH4)2M(PO3F)2(H2O)2 (M = Mg, Co) crystallize in the (NH4)2Cu(PO3F)2(H2O)2 type of structure (C2/m) and (NH4)2Mn(PO3F)2(H2O)2 in a subgroup thereof (P21/n, with a klassengleiche relationship of index 2), and NH4Cu2(H3O2)(PO3F)2 (C2/m) crystallizes isotypically with natrochalcite-type KCu2(H3O2)(SO4)2. A survey on the PO3F2− anion, including database entries of all inorganic compounds comprising this group, revealed mean bond lengths of P–O = 1.506(13) Å, P–F = 1.578(20) Å, and angles of O–P–O = 113.7(1.7)° and O–P–F = 104.8(1.7)°, using a dataset of 88 independent PO3F2− anions or entities. For those crystal structures of monofluorophosphates where hydrogen bonding is present, in the vast majority of cases, hydrogen bonds of the type D–H···F–P (D = O, N) are not developed.
      Citation: Chemistry
      PubDate: 2021-01-07
      DOI: 10.3390/chemistry3010005
      Issue No: Vol. 3, No. 1 (2021)
  • Chemistry, Vol. 3, Pages 74-93: Unveiling the Unexpected Reactivity of
           Electrophilic Diazoalkanes in [3+2] Cycloaddition Reactions within
           Molecular Electron Density Theory

    • Authors: Luis R. Domingo, Mar Ríos-Gutiérrez, Nivedita Acharjee
      First page: 74
      Abstract: The [3+2] cycloaddition (32CA) reactions of strongly nucleophilic norbornadiene (NBD), with simplest diazoalkane (DAA) and three DAAs of increased electrophilicity, have been studied within the Molecular Electron Density Theory (MEDT) at the MPWB1K/6-311G (d,p) computational level. These pmr-type 32CA reactions follow an asynchronous one-step mechanism with activation enthalpies ranging from 17.7 to 27.9 kcal·mol−1 in acetonitrile. The high exergonic character of these reactions makes them irreversible. The presence of electron-withdrawing (EW) substituents in the DAA increases the activation enthalpies, in complete agreement with the experimental slowing-down of the reactions, but contrary to the Conceptual DFT prediction. Despite the nucleophilic and electrophilic character of the reagents, the global electron density transfer at the TSs indicates rather non-polar 32CA reactions. The present MEDT study establishes the depopulation of the N–N–C core in this series of DAAs with the increase of the EW character of the substituents present at the carbon center is responsible for the experimentally found deceleration.
      Citation: Chemistry
      PubDate: 2021-01-10
      DOI: 10.3390/chemistry3010006
      Issue No: Vol. 3, No. 1 (2021)
  • Chemistry, Vol. 3, Pages 94-103: Lattice Dynamics of KAgF3 Perovskite,
           Unique 1D Antiferromagnet

    • Authors: Kacper Koteras, Jakub Gawraczyński, Mariana Derzsi, Zoran Mazej, Wojciech Grochala
      First page: 94
      Abstract: Theoretical DFT calculations using GGA+U and HSE06 frameworks enabled vibrational mode assignment and partial (atomic) phonon DOS determination in KAgF3 perovskite, a low-dimensional magnetic fluoroargentate(II). Twelve bands in the spectra of KAgF3 were assigned to either IR active or Raman active modes, reaching excellent correlation with experimental values (R2 > 0.997). Low-temperature Raman measurements indicate that the intriguing spin-Peierls-like phase transition at 230 K is an order–disorder transition and it does not strongly impact the vibrational structure of the material.
      Citation: Chemistry
      PubDate: 2021-01-19
      DOI: 10.3390/chemistry3010007
      Issue No: Vol. 3, No. 1 (2021)
  • Chemistry, Vol. 3, Pages 104-115: Synthesis and Photostability of
           Cyclooctatetraene-Substituted Free Base Porphyrins

    • Authors: Joanna Buczyńska, Agnieszka Gajewska, Aleksander Gorski, Barbara Golec, Krzysztof Nawara, Renata Rybakiewicz, Jacek Waluk
      First page: 104
      Abstract: A series of free base meso-tetraarylporphyrins functionalized with substituents containing one, two, and four cyclooctatetraene (COT) moieties have been obtained and characterized by spectral and photophysical studies. Three COT-free porphyrins served as reference compounds. COT is a triplet quencher, well-known to enhance the photostability of several, but not all, fluorophores. In the case of porphyrins, substitution with COT improves photostability in zinc derivatives, but for free bases, the effect is the opposite. We show that placing the COT moiety further from the free base porphyrin core enhances the photostability when the COT group lies in the direct vicinity of the macrocycle. The quantum yields of photobleaching inversely correlate with porphyrin oxidation potentials. An improvement in photostability in both COT-containing and COT-free porphyrins can be achieved by screening the porphyrin core from oxygen by switching from tolyl to mesityl substituents. This leads to a decrease in the photobleaching quantum yield, even though triplet lifetimes are longer. The results confirm the involvement of oxygen in the photodegradation of porphyrins.
      Citation: Chemistry
      PubDate: 2021-01-21
      DOI: 10.3390/chemistry3010008
      Issue No: Vol. 3, No. 1 (2021)
  • Chemistry, Vol. 3, Pages 116-125: Exchange Speed of Four-Component
           Nanorotors Correlates with Hammett Substituent Constants

    • Authors: Yi-Fan Li, Amit Ghosh, Pronay Kumar Biswas, Suchismita Saha, Michael Schmittel
      First page: 116
      Abstract: Three distinct four-component supramolecular nanorotors were prepared, using, for the first time, bipyridine instead of phenanthroline stations in the stator. Following our established self-sorting protocol to multicomponent nanodevices, the nanorotors were self-assembled by mixing the stator, rotators with various pyridine head groups, copper(I) ions and 1,4-diazabicyclo[2.2.2]octane (DABCO). Whereas the exchange of a phenanthroline vs. a bipyridine station did not entail significant changes in the rotational exchange frequency, the para-substituents at the pyridine head group of the rotator had drastic consequences on the speed: 4-OMe (k298 = 35 kHz), 4-H (k298 = 77 kHz) and 4-NO2 (k298 = 843 kHz). The exchange frequency (log k) showed an excellent linear correlation with both the Hammett substituent constants and log K of the copper(I)–ligand interaction, proving that rotator–copper(I) bond cleavage is the key determining factor in the rate-determining step.
      Citation: Chemistry
      PubDate: 2021-01-22
      DOI: 10.3390/chemistry3010009
      Issue No: Vol. 3, No. 1 (2021)
  • Chemistry, Vol. 3, Pages 126-137: Understanding Conformational
           Polymorphism in Ganciclovir: A Holistic Approach

    • Authors: Lorella Spiteri, Ulrich Baisch, Liana Vella-Zarb
      First page: 126
      Abstract: We present a holistic crystallographic study of the antiviral ganciclovir, including insights into its solid-state behavior, which could prove useful during drug development, making the process more sustainable. A newly developed methodology was used incorporating a combination of statistical and thermodynamic approaches, which can be applied to various crystalline materials. We demonstrate how the chemical environment and orientation of a functional group can affect its accessibility for participation in hydrogen bonding. The difference in the nature and strength of intermolecular contacts between the two anhydrous forms, exposed through full interaction maps and Hirshfeld surfaces, leads to the manifestation of conformational polymorphism. Variations in the intramolecular geometry and intermolecular interactions of both forms of ganciclovir were identified as possible predictors for their relative thermodynamic stability. It was shown through energy frameworks how the extensive supramolecular network of contacts in form I causes a higher level of compactness and lower enthalpy relative to form II. The likelihood of the material to exhibit polymorphism was assessed through a hydrogen bond propensity model, which predicted a high probability associated with the formation of other relatively stable forms. However, this model failed to classify the stability of form I appropriately, suggesting that it might not have fully captured the collective impacts which govern polymorphic stability.
      Citation: Chemistry
      PubDate: 2021-01-26
      DOI: 10.3390/chemistry3010010
      Issue No: Vol. 3, No. 1 (2021)
  • Chemistry, Vol. 3, Pages 138-145: A Versatile Tripodal Ligand for
           Sensitizing Lanthanide (LnIII) Ions and Color Tuning

    • Authors: Rodney A. Tigaa, Raul E. Ortega, Xinsong Lin, Geoffrey F. Strouse
      First page: 138
      Abstract: Lanthanide (LnIII) ions were successfully chelated and sensitized with a tripodal ligand. The absolute LnIII-centered emission efficiencies were ~3% for both the europium(III) (EuIII) and terbium (TbIII) complexes and up to 54% for the cerium(III) (CeIII) complex. The differences in emission quantum yields for the early lanthanides (CeIII) and the mid lanthanides (EuIII and TbIII) were attributed to their d–f and f–f nature, respectively. Despite the low quantum yield of the EuIII complex, the combination of the residual ligand fluorescence and the red EuIII emission resulted in a bluish-white material with the Commission Internationale de l’Eclairage (CIE) coordinates (0.258, 0.242). Thus, metal complexes of the ligand could be used in the generation of single-component white-light-emitting materials.
      Citation: Chemistry
      PubDate: 2021-01-26
      DOI: 10.3390/chemistry3010011
      Issue No: Vol. 3, No. 1 (2021)
  • Chemistry, Vol. 3, Pages 146-148: Acknowledgment to Reviewers of Chemistry
           in 2020

    • Authors: Chemistry Editorial Office Chemistry Editorial Office
      First page: 146
      Abstract: Peer review is the driving force of journal development, and reviewers are gatekeepers who ensure that Chemistry maintains its standards for the high quality of its published papers [...]
      Citation: Chemistry
      PubDate: 2021-01-26
      DOI: 10.3390/chemistry3010012
      Issue No: Vol. 3, No. 1 (2021)
  • Chemistry, Vol. 3, Pages 149-163: Exploring the Structural Chemistry of
           Pyrophosphoramides: N,N′,N″,N‴-Tetraisopropylpyrophosphoramide

    • Authors: Duncan Micallef, Liana Vella-Zarb, Ulrich Baisch
      First page: 149
      Abstract: N,N′,N″,N‴-Tetraisopropylpyrophosphoramide 1 is a pyrophosphoramide with documented butyrylcholinesterase inhibition, a property shared with the more widely studied octamethylphosphoramide (Schradan). Unlike Schradan, 1 is a solid at room temperature making it one of a few known pyrophosphoramide solids. The crystal structure of 1 was determined by single-crystal X-ray diffraction and compared with that of other previously described solid pyrophosphoramides. The pyrophosphoramide discussed in this study was synthesised by reacting iso-propyl amine with pyrophosphoryl tetrachloride under anhydrous conditions. A unique supramolecular motif was observed when compared with previously published pyrophosphoramide structures having two different intermolecular hydrogen bonding synthons. Furthermore, the potential of a wider variety of supramolecular structures in which similar pyrophosphoramides can crystallise was recognised. Proton (1H) and Phosphorus 31 (31P) Nuclear Magnetic Resonance (NMR) spectroscopy, infrared (IR) spectroscopy, mass spectrometry (MS) were carried out to complete the analysis of the compound.
      Citation: Chemistry
      PubDate: 2021-01-28
      DOI: 10.3390/chemistry3010013
      Issue No: Vol. 3, No. 1 (2021)
  • Chemistry, Vol. 3, Pages 164-181: Polymeric Bioinks for 3D Hepatic

    • Authors: Joyita Sarkar, Swapnil C. Kamble, Nilambari C. Kashikar
      First page: 164
      Abstract: Three-dimensional (3D) printing techniques have revolutionized the field of tissue engineering. This is especially favorable to construct intricate tissues such as liver, as 3D printing allows for the precise delivery of biomaterials, cells and bioactive molecules in complex geometries. Bioinks made of polymers, of both natural and synthetic origin, have been very beneficial to printing soft tissues such as liver. Using polymeric bioinks, 3D hepatic structures are printed with or without cells and biomolecules, and have been used for different tissue engineering applications. In this review, with the introduction to basic 3D printing techniques, we discuss different natural and synthetic polymers including decellularized matrices that have been employed for the 3D bioprinting of hepatic structures. Finally, we focus on recent advances in polymeric bioinks for 3D hepatic printing and their applications. The studies indicate that much work has been devoted to improvising the design, stability and longevity of the printed structures. Others focus on the printing of tissue engineered hepatic structures for applications in drug screening, regenerative medicine and disease models. More attention must now be diverted to developing personalized structures and stem cell differentiation to hepatic lineage.
      Citation: Chemistry
      PubDate: 2021-02-01
      DOI: 10.3390/chemistry3010014
      Issue No: Vol. 3, No. 1 (2021)
  • Chemistry, Vol. 3, Pages 182-198: Manipulating the Conformation of
           3,2′:6′,3″-Terpyridine in [Cu2(μ-OAc)4(3,2′:6′,3″-tpy)]n

    • Authors: Dalila Rocco, Samantha Novak, Alessandro Prescimone, Edwin C. Constable, Catherine E. Housecroft
      First page: 182
      Abstract: We report the preparation and characterization of 4′-([1,1′-biphenyl]-4-yl)-3,2′:6′,3″-terpyridine (1), 4′-(4′-fluoro-[1,1′-biphenyl]-4-yl)-3,2′:6′,3″-terpyridine (2), 4′-(4′-chloro-[1,1′-biphenyl]-4-yl)-3,2′:6′,3″-terpyridine (3), 4′-(4′-bromo-[1,1′-biphenyl]-4-yl)-3,2′:6′,3″-terpyridine (4), and 4′-(4′-methyl-[1,1′-biphenyl]-4-yl)-3,2′:6′,3″-terpyridine (5), and their reactions with copper(II) acetate. Single-crystal structures of the [Cu2(μ-OAc)4L]n 1D-coordination polymers with L = 1–5 have been determined, and powder X-ray diffraction confirms that the single crystal structures are representative of the bulk samples. [Cu2(μ-OAc)4(1)]n and [Cu2(μ-OAc)4(2)]n are isostructural, and zigzag polymer chains are present which engage in π-stacking interactions between [1,1′-biphenyl]pyridine units. 1D-chains nest into one another to give 2D-sheets; replacing the peripheral H in 1 by an F substituent in 2 has no effect on the solid-state structure, indicating that bifurcated contacts (H...H for 1 or H...F for 2) are only secondary packing interactions. Upon going from [Cu2(μ-OAc)4(1)]n and [Cu2(μ-OAc)4(2)]n to [Cu2(μ-OAc)4(3)]n, [Cu2(μ-OAc)4(4)]n, and [Cu2(μ-OAc)4(5)]n·nMeOH, the increased steric demands of the Cl, Br, or Me substituent induces a switch in the conformation of the 3,2′:6′,3″-tpy metal-binding domain, and a concomitant change in dominant packing interactions to py–py and py–biphenyl face-to-face π-stacking. The study underlines how the 3,2′:6′,3″-tpy domain can adapt to different steric demands of substituents through its conformational flexibility.
      Citation: Chemistry
      PubDate: 2021-02-02
      DOI: 10.3390/chemistry3010015
      Issue No: Vol. 3, No. 1 (2021)
  • Chemistry, Vol. 3, Pages 199-227: Functionalised Terpyridines and Their
           Metal Complexes—Solid-State Interactions

    • Authors: Young Hoon Lee, Jee Young Kim, Sotaro Kusumoto, Hitomi Ohmagari, Miki Hasegawa, Pierre Thuéry, Jack Harrowfield, Shinya Hayami, Yang Kim
      First page: 199
      Abstract: Analysis of the weak interactions within the crystal structures of 33 complexes of various 4′-aromatic derivatives of 2,2′:6′,2″-terpyridine (tpy) shows that interactions that exceed dispersion are dominated, as expected, by cation⋯anion contacts but are associated with both ligand–ligand and ligand–solvent contacts, sometimes multicentred, in generally complicated arrays, probably largely determined by dispersion interactions between stacked aromatic units. With V(V) as the coordinating cation, there is evidence that the polarisation of the ligand results in an interaction exceeding dispersion at a carbon bound to nitrogen with oxygen or fluorine, an interaction unseen in the structures of M(II) (M = Fe, Co, Ni, Cu, Zn, Ru and Cd) complexes, except when 1,2,3-trimethoxyphenyl substituents are present in the 4′-tpy.
      Citation: Chemistry
      PubDate: 2021-02-05
      DOI: 10.3390/chemistry3010016
      Issue No: Vol. 3, No. 1 (2021)
  • Chemistry, Vol. 3, Pages 228-237: Stereosopecificity in

    • Authors: Peter Osvath, Allen Oliver, A. Graham Lappin
      First page: 228
      Abstract: The X-ray structure of racemic [Co(sep)][Co(edta)]Cl2·2H2O is reported and reveals hetero-chiral stereospecificity in the interactions of [Co(sep)]3+ with [Co(edta)]−. Hydrogen-bonding along the molecular C2-axes of both complexes accounts for the stereospecificity. The structure of Λ-[Co(en)3]∆-[Co(edta)]2Cl·10H2O has been re-determined. Previous structural data for this compound were collected at room temperature and the model did not sufficiently describe the disorder in the structure. The cryogenic temperature used in the present study allows the disorder to be conformationally locked and modeled more reliably. A clearer inspection of other, structurally interesting, interactions is possible. Again, hydrogen-bonding along the molecular C2-axis of [Co(en)3]3+ and the equatorial carboxylates of [Co(edta)]− is the important interaction. The unique nature of the equatorial carboxylates and molecular C2-axis in [Co(edta)]−, straddled by two pseudo-C3-faces where the arrangement of the carboxylate groups conveys the same helicity, is highlighted. Implications of these structures in understanding stereoselectivity in ion-pairing and electron transfer reactions are discussed.
      Citation: Chemistry
      PubDate: 2021-02-06
      DOI: 10.3390/chemistry3010017
      Issue No: Vol. 3, No. 1 (2021)
  • Chemistry, Vol. 3, Pages 238-255: Effects of Substituents on Photophysical
           and CO-Photoreleasing Properties of 2,6-Substituted meso-Carboxy BODIPY

    • Authors: Esther M. Sánchez-Carnerero, Marina Russo, Andreas Jakob, Lucie Muchová, Libor Vítek, Petr Klán
      First page: 238
      Abstract: Carbon monoxide (CO) is an endogenously produced signaling molecule involved in the control of a vast array of physiological processes. One of the strategies to administer therapeutic amounts of CO is the precise spatial and temporal control over its release from photoactivatable CO-releasing molecules (photoCORMs). Here we present the synthesis and photophysical and photochemical properties of a small library of meso-carboxy BODIPY derivatives bearing different substituents at positions 2 and 6. We show that the nature of substituents has a major impact on both their photophysics and the efficiency of CO photorelease. CO was found to be efficiently released from π-extended 2,6-arylethynyl BODIPY derivatives possessing absorption spectra shifted to a more biologically desirable wavelength range. Selected photoCORMs were subjected to in vitro experiments that did not reveal any serious toxic effects, suggesting their potential for further biological research.
      Citation: Chemistry
      PubDate: 2021-02-09
      DOI: 10.3390/chemistry3010018
      Issue No: Vol. 3, No. 1 (2021)
  • Chemistry, Vol. 3, Pages 256-268: Neutral and Cationic Chelidonate
           Coordination Polymers with N,N′-Bridging Ligands

    • Authors: Rosa Carballo, Ana Belén Lago, Arantxa Pino-Cuevas, Olaya Gómez-Paz, Nuria Fernández-Hermida, Ezequiel M. Vázquez-López
      First page: 256
      Abstract: The biomolecule chelidonic acid (H2chel, 4-oxo-4H-pyran-2,6-dicarboxylic acid) has been used to build new coordination polymers with the bridging N,N′-ligands 4,4′-bipyridine (4,4-bipy) and 1,2-bis(4-pyridyl)ethane (bpe). Four compounds have been obtained as single crystals: 1D cationic coordination polymers [M(4,4-bipy)(OH2)4]2+ with chelidonate anions and water molecules in the second coordination sphere in 1∞[Zn(4,4-bipy)(H2O)4]chel·3H2O (2) and in the two pseudopolymorphic 1∞[Cu(4,4-bipy)(H2O)4]chel·nH2O (n = 3, 4a; n = 6, 4b), and the 2D neutral coordination polymers 2∞[Zn(chel)(4,4-bipy)(H2O)]·2H2O (1) and 2∞[Zn(chel)(bpe)(H2O)]·H2O (3) where the chelidonate anion acts as a bridging ligand. The effects of the hydrogen bonds on the crystal packing were analyzed. The role of the water molecules hosted within the crystals lattices was also studied.
      Citation: Chemistry
      PubDate: 2021-02-11
      DOI: 10.3390/chemistry3010019
      Issue No: Vol. 3, No. 1 (2021)
  • Chemistry, Vol. 3, Pages 269-287: Dimensionality Control in Crystalline
           Zinc(II) and Silver(I) Complexes with Ditopic Benzothiadiazole-Dipyridine

    • Authors: Teodora Mocanu, Nataliya Plyuta, Thomas Cauchy, Marius Andruh, Narcis Avarvari
      First page: 269
      Abstract: Three 2,1,3-benzothiadiazole-based ligands decorated with two pyridyl groups, 4,7-di(2-pyridyl)-2,1,3-benzothiadiazol (2-PyBTD), 4,7-di(3-pyridyl)-2,1,3-benzothiadiazol (3-PyBTD) and 4,7-di(4-pyridyl)-2,1,3 benzothiadiazol (4-PyBTD), generate ZnII and AgI complexes with a rich structural variety: [Zn(hfac)2(2-PyBTD)] 1, [Zn2(hfac)4(2-PyBTD)] 2, [Ag(CF3SO3)(2-PyBTD)]23, [Ag(2-PyBTD)]2(SbF6)24, [Ag2(NO3)2(2-PyBTD)(CH3CN)] 5, [Zn(hfac)2(3-PyBTD)] 6, [Zn(hfac)2(4-PyBTD)] 7, [ZnCl2(4-PyBTD)2] 8 and [ZnCl2(4-PyBTD)] 9 (hfac = hexafluoroacetylacetonato). The nature of the resulting complexes (discrete species or coordination polymers) is influenced by the relative position of the pyridyl nitrogen atoms, the nature of the starting metal precursors, as well as by the synthetic conditions. Compounds 1 and 8 are mononuclear and 2, 3 and 4 are binuclear species. Compounds 6, 7 and 9 are 1D coordination polymers, while compound 5 is a 2D coordination polymer, the metal ions being bridged by 2-PyBTD and nitrato ligands. The solid-state architectures are sustained by intermolecular π–π stacking interactions established between the pyridyl group and the benzene ring from the benzothiadiazol moiety. Compounds 1, 2, 7–9 show luminescence in the visible range. Density Functional Theory (DFT) and Time Dependent Density Functional Theory (TD-DFT) calculations have been performed on the ZnII complexes 1 and 2 in order to disclose the nature of the electronic transitions and to have an insight on the modulation of the photophysical properties upon complexation.
      Citation: Chemistry
      PubDate: 2021-02-12
      DOI: 10.3390/chemistry3010020
      Issue No: Vol. 3, No. 1 (2021)
  • Chemistry, Vol. 3, Pages 288-295: Tetra Schiff Bases as Polyvinyl Chloride
           Thermal Stabilizers

    • Authors: Dina S. Ahmed, Mohammed Kadhom, Angham G. Hadi, Muna Bufaroosha, Nadia Salih, Wedad H. Al-Dahhan, Emad Yousif
      First page: 288
      Abstract: Tetra Schiff bases were used as thermal stabilizers to enhance the properties of polyvinyl chloride (PVC) when operated at high temperatures. The thermal stability of PVC films doped with Schiff bases was tested by the weight-loss method, Fourier transform infrared (FTIR) spectroscopy, thermal aging test, optical microscope, and atomic force microscope (AFM). Results showed that embedding these additives increased the stability time of the polymer, which decreased the degradation reaction tendency. Furthermore, the primary color of PVC was improved by adding the Schiff bases using oven-aging. In addition, these Schiff bases resulted in a significant reduction in PVC’s conjugated double bonds and, hence, the weight loss.
      Citation: Chemistry
      PubDate: 2021-02-17
      DOI: 10.3390/chemistry3010021
      Issue No: Vol. 3, No. 1 (2021)
  • Chemistry, Vol. 3, Pages 296-313: Electronically Excited States of

    • Authors: Taylor J. Santaloci, Ryan C. Fortenberry
      First page: 296
      Abstract: Few anions exhibit electronically excited states, and, if they do, the one or two possible excitations typically transpire beyond the visible spectrum into the near-infrared. These few, red-shifted electronic absorption features make anions tantalizing candidates as carriers of the diffuse interstellar bands (DIBs), a series of mostly unknown, astronomically ubiquitous absorption features documented for over a century. The recent interstellar detection of benzonitrile implies that cyano-functionalized polycyclic aromatic hydrocarbon (PAH) anions may be present in space. The presently reported quantum chemical work explores the electronic properties of deprotonated benzene, naphthalene, and anthracene anions functionalized with a single cyano group. Both the absorption and emission properties of the electronically excited states are explored. The findings show that the larger anions absorption and emission energies possess both valence and dipole bound excitations in the 450–900 nm range with oscillator strengths for both types of >1×10−4. The valence and dipole bound excited state transitions will produce slightly altered substructure from one another making them appear to originate with different molecules. The known interstellar presence of related molecules, the two differing natures of the excited states for each, and the wavelength range of peaks for these cyano-functionalized PAH anions are coincident with DIB properties. Finally, the methods utilized appear to be able to predict the presence of dipole-bound excited states to within a 1.0 meV window relative to the electron binding energy.
      Citation: Chemistry
      PubDate: 2021-02-23
      DOI: 10.3390/chemistry3010022
      Issue No: Vol. 3, No. 1 (2021)
  • Chemistry, Vol. 3, Pages 314-326: Cluster-Based Coordination Polymers of
           Mn/Fe-Oxo Pivalates and Isobutyrates

    • Authors: Svetlana Baca, Paul Kögerler
      First page: 314
      Abstract: Polynuclear coordination clusters can be readily arranged in cluster-based coordination polymers (CCPs) by appropriate bridging linkers. This review provides an overview of our recent developments in exploring structurally well-defined Mn/Fe-oxo pivalate and isobutyrate building blocks in the formation of CCPs assemblies with an emphasis on synthetic strategies and magnetic properties.
      Citation: Chemistry
      PubDate: 2021-02-24
      DOI: 10.3390/chemistry3010023
      Issue No: Vol. 3, No. 1 (2021)
  • Chemistry, Vol. 3, Pages 327-337: Fluorescent Detection of Carbon
           Disulfide by a Highly Emissive and Robust Isoreticular Series of Zr-Based
           Luminescent Metal Organic Frameworks (LMOFs)

    • Authors: Ever Velasco, Yuki Osumi, Simon J. Teat, Stephanie Jensen, Kui Tan, Timo Thonhauser, Jing Li
      First page: 327
      Abstract: Carbon disulfide (CS2) is a highly volatile neurotoxic species. It is known to cause atherosclerosis and coronary artery disease and contributes significantly to sulfur-based pollutants. Therefore, effective detection and capture of carbon disulfide represents an important aspect of research efforts for the protection of human and environmental health. In this study, we report the synthesis and characterization of two strongly luminescent and robust isoreticular metal organic frameworks (MOFs) Zr6(µ3-O)4(OH)8(tcbpe)2(H2O)4 (here termed 1) and Zr6(µ3-O)4(OH)8(tcbpe-f)2(H2O)4 (here termed 2) and their use as fluorescent sensors for the detection of carbon disulfide. Both MOFs demonstrate a calorimetric bathochromic shift in the optical bandgap and strong luminescence quenching upon exposure to carbon disulfide. The interactions between carbon disulfide and the frameworks are analyzed by in-situ infrared spectroscopy and computational modelling by density functional theory. These results reveal that both the Zr metal node and organic ligand act as the preferential binding sites and interact strongly with carbon disulfide.
      Citation: Chemistry
      PubDate: 2021-03-01
      DOI: 10.3390/chemistry3010024
      Issue No: Vol. 3, No. 1 (2021)
  • Chemistry, Vol. 3, Pages 338-359: Towards High Efficacy of Pd-Au/C
           Catalyst for Tetrachloromethane Hydrodechlorination

    • Authors: Magdalena Bonarowska, Zbigniew Kaszkur, Krzysztof Matus, Alicja Drelinkiewicz, Tomasz Szumełda, Adam Kubas
      First page: 338
      Abstract: We present an efficient strategy for synthesising the PdAu catalysts with a homogeneous PdAu alloy phase for environmentally important hydrodechlorination of tetrachloromethane in the gas phase. The synthesis of carbon-supported catalysts involved two major steps: (i) incorporation of palladium and gold nanoparticles into carbon support and (ii) activation of the catalysts. The critical part of this work was to find the optimal conditions for both steps. Thus, the incorporation of the nanoparticles was carried out in two ways, by impregnation and direct redox reaction method using acetone solutions of metal precursor salts. The activation was performed either by a conventional thermal reduction in hydrogen or flash irradiation in a microwave oven. The homogeneity and structure of the PdAu alloy were found to depend on the catalyst activation method critically. In all cases, we observed better homogeneity for catalysts that were subject to microwave irradiation. Moreover, the flash microwave irradiation of prepared catalysts provided catalysts of better stability and selectivity towards the desired products (hydrocarbons) in the hydrodechlorination of tetrachloromethane as compared to the catalyst obtained by conventional thermal activation in hydrogen.
      Citation: Chemistry
      PubDate: 2021-03-01
      DOI: 10.3390/chemistry3010025
      Issue No: Vol. 3, No. 1 (2021)
  • Chemistry, Vol. 3, Pages 360-372: Spin-Crossover 2-D Hofmann Frameworks
           Incorporating an Amide-Functionalized Ligand: N-(pyridin-4-yl)benzamide

    • Authors: Xandria Ong, Manan Ahmed, Luonan Xu, Ashley T. Brennan, Carol Hua, Katrina A. Zenere, Zixi Xie, Cameron J. Kepert, Benjamin J. Powell, Suzanne M. Neville
      First page: 360
      Abstract: Two analogous 2-D Hofmann-type frameworks, which incorporate the novel ligand N-(pyridin-4-yl)benzamide (benpy) [FeII(benpy)2M(CN)4]·2H2O (M = Pd (Pd(benpy)) and Pt (Pt(benpy))) are reported. The benpy ligand was explored to facilitate spin-crossover (SCO) cooperativity via amide group hydrogen bonding. Structural analyses of the 2-D Hofmann frameworks revealed benpy-guest hydrogen bonding and benpy-benpy aromatic contacts. Both analogues exhibited single-step hysteretic spin-crossover (SCO) transitions, with the metal-cyanide linker (M = Pd or Pt) impacting the SCO spin-state transition temperature and hysteresis loop width (Pd(benpy): T½↓↑: 201, 218 K, ∆T: 17 K and Pt(benpy): T½↓↑: 206, 226 K, ∆T: 20 K). The parallel structural and SCO changes over the high-spin to low-spin transition were investigated using variable-temperature, single-crystal, and powder X-ray diffraction, Raman spectroscopy, and differential scanning calorimetry. These studies indicated that the ligand–guest interactions facilitated by the amide group acted to support the cooperative spin-state transitions displayed by these two Hofmann-type frameworks, providing further insight into cooperativity and structure–property relationships.
      Citation: Chemistry
      PubDate: 2021-03-01
      DOI: 10.3390/chemistry3010026
      Issue No: Vol. 3, No. 1 (2021)
  • Chemistry, Vol. 3, Pages 373-381: Discovery of Novel 1,2,4-Oxadiazole
           Derivatives as Potent Caspase-3 Activator for Cancer Treatment

    • Authors: Ankur Vaidya
      First page: 373
      Abstract: In the present study, a quantitative structure–activity relationship (QSAR) and docking studies were accomplished on a series of 1,2,4-oxadiazoles. The results of QSARs are reliable and have high predictive ability for both the internal (q2 = 0.610) and external (pred_r2 = 0.553) datasets with least standard error (SE; i.e., 0.130) and four principal components, which signifies the reliability of the generated model. Molecular docking was also reported by the GOLD docking program, which showed that the hydrogen bonding may be responsible for the activity, and may be further increased upon adding high electronegative substitutions.
      Citation: Chemistry
      PubDate: 2021-03-08
      DOI: 10.3390/chemistry3010027
      Issue No: Vol. 3, No. 1 (2021)
  • Chemistry, Vol. 3, Pages 382-390: Adsorption of Polymer-Grafted
           Nanoparticles on Curved Surfaces

    • Authors: Aye Ozmaian, Rob D. Coalson, Masoumeh Ozmaian
      First page: 382
      Abstract: Nanometer-curved surfaces are abundant in biological systems as well as in nano-sized technologies. Properly functionalized polymer-grafted nanoparticles (PGNs) adhere to surfaces with different geometries and curvatures. This work explores some of the energetic and mechanical characteristics of the adhesion of PGNs to surfaces with positive, negative and zero curvatures using Coarse-Grained Molecular Dynamics (CGMD) simulations. Our calculated free energies of binding of the PGN to the curved and flat surfaces as a function of separation distance show that curvature of the surface critically impacts the adhesion strength. We find that the flat surface is the most adhesive, and the concave surface is the least adhesive surface. This somewhat counterintuitive finding suggests that while a bare nanoparticle is more likely to adhere to a positively curved surface than a flat surface, grafting polymer chains to the nanoparticle surface inverts this behavior. Moreover, we studied the rheological behavior of PGN upon separation from the flat and curved surfaces under external pulling force. The results presented herein can be exploited in drug delivery and self-assembly applications.
      Citation: Chemistry
      PubDate: 2021-03-08
      DOI: 10.3390/chemistry3010028
      Issue No: Vol. 3, No. 1 (2021)
  • Chemistry, Vol. 3, Pages 391-401: QSAR Modelling of Peptidomimetic
           Derivatives towards HKU4-CoV 3CLpro Inhibitors against MERS-CoV

    • Authors: Imad Hammoudan, Soumaya Matchi, Mohamed Bakhouch, Salah Belaidi, Samir Chtita
      First page: 391
      Abstract: In this paper, we report the relationship between the anti-MERS-CoV activities of the HKU4 derived peptides for some peptidomimetic compounds and various descriptors using the quantitative structure activity relationships (QSAR) methods. The used descriptors were computed using ChemSketch, Marvin Sketch and ChemOffice software. The principal components analysis (PCA) and the multiple linear regression (MLR) methods were used to propose a model with reliable predictive capacity. The original data set of 41 peptidomimetic derivatives was randomly divided into training and test sets of 34 and 7 compounds, respectively. The predictive ability of the best MLR model was assessed by determination coefficient R2 = 0.691, cross-validation parameter Q2cv = 0.528 and the external validation parameter R2test = 0.794.
      Citation: Chemistry
      PubDate: 2021-03-09
      DOI: 10.3390/chemistry3010029
      Issue No: Vol. 3, No. 1 (2021)
  • Chemistry, Vol. 3, Pages 402-410: Synthesis and Structure-Chirality
           Relationship Analysis of Steroidal Quinoxalines to Design and Develop New
           Chiral Drugs

    • Authors: Rashid Mehmood, Naghmana Rashid, Shakir Ullah, Maria John Newton Amaldoss, Charles Christopher Sorrell
      First page: 402
      Abstract: Of the utmost importance of chirality in organic compounds and drugs, the present work reports structure-chirality relationship of three steroidal quinoxalines, which were synthesised by condensing diaminobenzenes with cholestenone. All the compounds were purified and characterised by varying analytical tools prior to their chiroptical analysis by circular dichroism (CD) technique. The substituent groups on quinoxalines contributed to determining the chiroptical properties of the compounds. The positive Cotton effects have been observed in the CD spectra of unsubstituted and methyl-substituted quinoxalines, which indicated their P helicity. Importantly, chloro-substituent on quinoxalines produced different CD behaviour, which can be attributed to the presence of three lone pairs of electrons on Cl atom. The present work provides guidelines for determining the chiral properties of steroidal quinoxalines, which can be useful to design and develop potential molecules of biological importance.
      Citation: Chemistry
      PubDate: 2021-03-15
      DOI: 10.3390/chemistry3010030
      Issue No: Vol. 3, No. 1 (2021)
  • Chemistry, Vol. 3, Pages 411-439: New Syntheses, Analytic Spin
           Hamiltonians, Structural and Computational Characterization for a Series
           of Tri-, Hexa- and Hepta-Nuclear Copper (II) Complexes with Prototypic

    • Authors: Ana Maria Toader, Maria Cristina Buta, Fanica Cimpoesu, Andrei-Iulian Toma, Christina Marie Zalaru, Ludmila Otilia Cinteza, Marilena Ferbinteanu
      First page: 411
      Abstract: We present a series of pyrazolato-bridged copper complexes with interesting structures that can be considered prototypic patterns for tri-, hexa- and hepta- nuclear systems. The trinuclear shows an almost regular triangle with a μ3-OH central group. The hexanuclear has identical monomer units, the Cu6 system forming a regular hexagon. The heptanuclear can be described as two trinuclear moieties sandwiching a central copper ion via carboxylate bridges. In the heptanuclear system, the pyrazolate bridges are consolidating the triangular faces, which are sketching an elongated trigonal antiprism. The magnetic properties of these systems, dominated by the strong antiferromagnetism along the pyrazolate bridges, were described transparently, outlining the energy levels formulas in terms of Heisenberg exchange parameters J, within the specific topologies. We succeeded in finding a simple Kambe-type resolution of the Heisenberg spin Hamiltonian for the rather complex case of the heptanuclear. In a similar manner, the weak intermolecular coupling of two trimer units (aside from the strong exchange inside triangles) was resolved by closed energy formulas. The hexanuclear can be legitimately proposed as a case of coordination-based aromaticity, since the phenomenology of the six-spins problem resembles the bonding in benzene. The Broken-Symmetry Density Functional Theory (BS-DFT) calculations are non-trivial results, being intrinsically difficult at high nuclearities.
      Citation: Chemistry
      PubDate: 2021-03-15
      DOI: 10.3390/chemistry3010031
      Issue No: Vol. 3, No. 1 (2021)
  • Chemistry, Vol. 3, Pages 440-443: Tribute to Josef Michl

    • Authors: Igor Alabugin, Petr Klán
      First page: 440
      Abstract: It is our great pleasure to introduce the Festschrift of Chemistry to honor professor Josef Michl (Figure 1) on the occasion of his 80th birthday and to recognize his exceptional contributions to the fields of organic photochemistry, quantum chemistry, biradicals and biradicaloids, electronic and vibrational spectroscopy, magnetic circular dichroism, silicon and boron chemistry, supramolecular chemistry, singlet fission, and molecular machines [...]
      Citation: Chemistry
      PubDate: 2021-03-22
      DOI: 10.3390/chemistry3010032
      Issue No: Vol. 3, No. 1 (2021)
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