A DFT investigation of conformational geometries a

Authors: Vithaya Ruangpornvisuti Banchob Wanno

Publish Date: 2004/11/19

Volume: 10, Issue: 5-6, Pages: 418-426

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Abstract

The geometrical structures of phenylthiosemicarbazone HAPhTSC conformers have been obtained by geometry optimizations using density functional theory DFT calculations at the B3LYP/631Gd and B3LYP/6311Gdp levels of theory Six thioamino and 24 thioimino tautomers of HAPhTSC have been found Six tautomerization reactions between thioamino and thioimino tautomers occurring via transition states and their corresponding activation energies have been obtained Conformational pathways for tautomerizations and interconversions of HAPhTSC conformers have been presented Tautomerization between the most stable species of thioamino Atttcc and its thioimino Itttcct tautomer is an endothermic reaction ΔH0=1817 kcal mol−1 and its log K=−1374 at 29815 K Thermodynamic quantities of tautomerizations interconversions of HAPhTSC conformers and their equilibrium constants are reported The geometry of the zinc complex with HAPhTSC found as a ZnHAPhTSC2Cl2 structure has been obtained using B3LYP/631Gd calculations Binding of the ZnHAPhTSC2Cl2 complex is an exothermic and spontaneous reactionFigure Conformational notation defined as a name consisting of a letter “A” for a thioamino tautomer followed by “c” for cis or “t” for trans isomerism of five dihedral angles of χC4C3C2N3 ϕC3C2N3N2 ψC2N3N2C1 θN3N2C1N1 and ωN2C1N1H2 serially or a letter “I” for b thioimino tautomer followed by “c” for cis or “t” for trans isomerism of six dihedral angles of χC4C3C2N3 ϕC3C2N3N2 ψC2N3N2C1 θN3N2C1N1 ωN2C1N1H2 and δ N2C1SH1 serially

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