Vibrational analysis, frontier orbitals, optical and structural properties of 1, 2-dithiete and di-thiolene derivatives: A quantum mechanical study

Abstract

The organic chemistry of sulfur-containing compounds has attracted much research due to its importance in biology, biochemistry, and various industries. 1, 2-Dithiete is a cyclic and unsaturated organo-sulfuric compound. This compound can be converted to di-thiolene (its valence isomer). The structure, electronic properties, and energy of two valence isomers, i.e. di-thiolene and 1,2-dithiete (III) were studied using density functional theory (DFT). Results showed that di-thiolene has two conformers (s-trans (I), s-cis (II)) and the s-trans is more stable. The electron donor and acceptor substituents on the carbon atoms increase the polarity difference between these two valence isomers. The dipole moment and polarizability of di-thiolenes were also greater than those of 1, 2-dithietes. Conversion of 1,2-dithiete to di-thiolene, structural properties, polarity, and polarizability of some derivatives of these two valence isomers were examined by quantum mechanical method at the level of B3LYP theory and 6-311++g (d, p) bases sets using Gaussian09 computational program. This conversion occurs through the s-cis conformation pathway and is an exothermic reaction. In the cases of ten derivatives of C2S2R2 (R = CH3, CF3, CN, OCH3, CH2CH3, t-Bu, Ph, Cyclopropyl, Cyclobutyl, and Cyclopentyl) the s-cis conformers are so unstable that they are not obtained as local structures. In general, s-trans di-thiolenes are more stable than their cyclic valence isomers (1,2-dithietes). Of course, the degree of stability depends on substituent identity.