DFT Study and NBO Analysis of Conformation Properties of 2,5,5-Trimethyl-1,3,2-Dioxaphosphinane 2-Selenide and Their Dithia and Diselena Analogous

Abstract

The hybrid density functional theory (B3LYP) and ab initio molecular orbital (HF) based methods and Natural Bond Orbital (NBO) interpretation were used to analyze the conformational behaviors of 2,5,5-trimethyl-1,3,2-dioxaphosphinane 2-selenide (compound <strong>1</strong>), 2,5,5-trimethyl-1,3,2-dithiaphosphinane 2-selenide (compound <strong>2</strong>) and 2,5,5-trimethyl-1,3,2-diselena phosphinane 2-selenide (compound <strong>3</strong>). The results explained that the axial conformations had a preference of compounds <strong>1-3</strong>. The relative energies ∆<em>E₀</em>and Gibbs free energy difference values <em>(ΔG_eq-ax) </em>between the ax and eq-conformations were calculated and showed the decrease from compound <strong>1 </strong>to <strong>3</strong>. Stereo electronic effect (<em>SE</em>) for <strong>1</strong> to <strong>3</strong> has been calculated by the NBO analysis. Therefore, in this study, other factors such as stereo electronic effects, electrostatic and steric interactions of compounds <strong>1</strong> to <strong>3</strong> conformational behavior have been evaluated. One examined whether the stereo electronic effect is the only factor affecting the conformational behavior or not? The electronic properties such as the HOMO and LUMO energies were also determined to investigate the reactive sites of the compounds. Structural-relative activities of compounds are also evaluated.