In this paper, the frontier hybrid orbitals (FBO's) of a series of octahedral ML5 fragments are used to discuss the electronic structure and the chemical bond of these fragments and the molecules built of these ML5 fragments. The bond orbitals which are chosen as the linear combination of the frontier hybrid orbitals . of fragments are calculated and explain the electronic structure and propert...

The crystal and molecular structures of three new thiosemicarbazones, 2-[1-(2-hydroxy-5-methoxyphenyl)ethylidene]-N-methyl-hydrazinecarbothioamide monohydrate (1), 2-[1-(2-hydroxy-5-methoxyphenyl)ethylidene]-N-ethyl-hydrazinecarbothioamide (2) and 2-[1-(2-hydroxy-4-methoxyphenyl)ethylidene]-N-ethyl-hydrazinecarbothioamide acetonitrile solvate (3), are reported and confirmed by single crystal X-...

Charge transport through a molecular junction comprising an oligomer of p-phenylene-vinylene between gold contacts has been investigated using density-functional theory and the nonequilibrium Green’s function method. The influence of the contact gap geometry on the transport has been studied for elongated and contracted gaps, as well as various molecular conformations. The calculated current-vo...

Dynamic behaviors of chemical concepts in density functional theory such as frontier orbitals (HOMO/LUMO), chemical potential, hardness, and electrophilicity index have been investigated in this work in the context of Bohn-Oppenheimer quantum molecular dynamics in association with molecular conformation changes. Exemplary molecular systems like CH5 , Cl (H2O)30 and Ca 2+ (H2O)15 are studied at ...

Semiempirical CNDO/2 calculations of the electronic and molecular structures have been carried out for six antitumor anthracycline antibiotics. The strong correlation between their biological activity and such molecular properties as chromophore dipole moment, energy of frontier orbitals, and steric volumes was found and the proper QSAR equations were constructed. The molecular mechanics model ...

The class of compounds (RCp)2MX2, where M is a group IV metal, Cp is cyclopentadienyl, R is an alkyl, and X is a halide, has been of continuing interest as precursors for olefin coordination polymerization catalysts. In this communication, we demonstrate that the technique of optically detected magnetic resonance (ODMR) reveals subtle differences in the composition of the frontier molecular orb...

The G-quadruplexes are four-stranded nucleic acid structures with guanine-rich sequences that play important biological roles in, for example, regulating telomerase association and activity. Recent evidence supports the hypothesis that the telomeric G-quadruplex DNA represents a target of novel anticancer drug medication. In this work, we present results of the molecular electrostatic potential...

Density functional theory investigations indicate that carbon boronyls (CBO)n (n = 3-7) are considerably more stable in thermodynamics than their boron carbonyl isomers (BCO)n and exhibit aromaticity throughout the whole series. The extra stabilities of (CBO)n originate from their frontier pi molecular orbitals delocalized over the Dnh Cn central rings which are absent in (BCO)n. It is expected...

We study the electronic structure of (n,0) zigzag carbon nanotubes by means of two complementary numerical methods. Using the semiempirical PM3 method, we carry out quantum-chemical calculations for tube fragments of different symmetry and size, which represent these tubes. Using the tight-binding method, we proceed in parallel to determine the band structure of these tubes. The effect of clust...