China
Africa
Explore chapters and articles related to this topic
Introduction
Published in Vlad P. Shmerko, Svetlana N. Yanushkevich, Sergey Edward Lyshevski, Computer Arithmetics for Nanoelectronics, 2018
Vlad P. Shmerko, Svetlana N. Yanushkevich, Sergey Edward Lyshevski
Molecular recognition, complementarity, and aggregation are well-established and sound principles. Molecular recognition implies the specific interaction between two or more molecules by means noncovalent (hydrogen bonding, metal coordination, hydrophobic forces, van der Waals forces, pi-pi interactions, electrostatic forces, etc.), and covalent bonds. For example, molecular recognition and molecular complementarity, exhibited by DNA, amino acids, and other biomolecules, can be significantly expanded utilizing organic and inorganic molecules. Stereochemistry studies the spatial arrangement of atoms, molecules, and molecular aggregates.
Mathematical analysis of one-dimensional lead sulphide crystal structure using molecular graph theory
Published in Molecular Physics, 2022
Yogesh Singh, Sunny Kumar Sharma, Purnima Hazra
Mathematical chemistry is a field of study that focuses on new mathematical applications in chemistry. It is primarily concerned with the mathematical modelling of chemical phenomena which include molecular graphs and their topological indices. This is concerned with topologies, such as the mathematical study of isomerism and the establishment of topological indices or descriptors that are used in quantitative structure–property relationships. Secondly, there are chemical aspects of group theory, which are useful in quantum chemistry and stereochemistry. Apart, topological indices are invariants that are used to study the properties of chemical compounds, which results in understanding the structural formula of chemical compounds. In a molecular graph, the atoms of a chemical compound are represented by the vertices of a graph, while the chemical bonds are represented by the edges [6].
Synthesis and characterization of sodium, potassium, zinc and aluminium formamidinate complexes
Published in Journal of Coordination Chemistry, 2021
Mehdi Salehisaki, Nazli E. Rad, Peter C. Junk, Glen B. Deacon, Jun Wang
[Zn4(PhForm)6O]·2.5thf (Zn1) crystallized in the triclinic space group P-1 with one whole tetranuclear molecule occupying the asymmetric unit (Figure 5). It contrasts the reported Zn1·1.45hexane solvate, which crystallized in the orthorhombic Pbca space group [12]. In the cage structure, a central oxygen atom is surrounded by four zinc ions, which are four coordinate with distorted tetrahedral stereochemistry. There are six μ-1κ(N):2κ(N’) ligands, three nitrogen atoms of which bind to each zinc ion, which also binds to the central oxygen. The metrical parameters for Zn-N and Zn-O bonds correspond closely to those reported for the hexane solvate [12], other than marginally less variation, hence they require no further discussion. Presumably the oxygen arises from fortuitous oxygen or water with the stability of the cage making it a good oxygen scavenger. An homoleptic zinc formamidinate [Zn(DippForm)2] has been prepared with the bulkier DippForm ligand, but other Zn/DippForm/oxy species were also obtained [26].
3-Functional substituted 4-trifluoromethyl tetrahydrothiophenes via [3 + 2]-cycloaddition reactions
Published in Journal of Sulfur Chemistry, 2019
Yuriy M. Markitanov, Vadim M. Timoshenko, Tymofii V. Rudenko, Eduard B. Rusanov, Yuriy G. Shermolovich
Functionalization of sulfide moiety in thiolanes 4 was carried out by the oxidation and oxidative imination reactions. Tetrahydrothiophene 4d was converted to corresponding S-oxide 5, as a mixture of diastereomers (1.05:1), and S,S-dioxide 6 using meta-chloroperoxybenzoic acid as an oxidant (Scheme 1). Next we examined oxidative imination of the obtained tetrahydrothiophenes, which opened access to cyclic sulfoximines. A straightforward procedure for the preparation of NH-sulfoximines applied for 4a,d, via simultaneous transfer of O and NH group [26] involving diacetoxyiodobenzene as an oxidant and ammonium carbamate as ammonia source (Scheme 1), gave 4-(trifluoromethyl)tetrahydrothiophen-3-yl-S-imino-S-oxides 7a,b in 57%–65% isolated yields. Since an oxidative imination reaction of sulfides generates new stereogenic center, we expected the formation of two diastereomers for compounds 7a,b. Indeed, sulfoximine 7a was isolated as a mixture of diastereomers (1.25:1) with different stereochemistry of sulfur atom. In the case of sulfoximine 7b one diastereomer precipitated directly from the reaction mixture, while an isolation of another isomer from the mother liquor was complicated. The structures of both sulfoximines 7a,b were successfully confirmed by NMR spectra, mass spectroscopy data and elemental analysis.