DFT Study and NBO Analysis on Conformers of 1,3,2-Dithiaphosphane -2-Sulfide derivatives

Stereoelectronic interactions associated with Generalized anomeric effect (GAE) and electrostatic effect on the conformational behaviors of 2,5,5-trimethyl-1,3,2-dioxaphosphinane 2-sulfide (1), - dithiaphosphinane 2- sulfide (2) and -diselenaphosphinane 2- sulfide (3) were investigated using DFT (Density Functional Theory) method. These compounds have been analyzed by means of DFT method and natural bond orbital (NBO) interpretation. These compounds were fully optimized with DFT: B3LYP method using 6-311+G∗∗ and 6-31G∗∗ basis sets. Both basis sets showed that the Gibbs free energy difference values (ΔGeq-ax) between the axial and equatorial conformers decreases from compounds 1 to 3. Based on results obtained from the NBO analysis, stereoelectronic effect corresponding to the naxX→σ*P-C electron delocalization in the equatorial conformations and naxX→σ*P-S in the axial conformations have the highest level of stability energy, where X= [O, S, Se]. Stereoelectronic effect through the naxX→σ*P-S interaction is of major relation or impressive to demonstrate conformational preference in the specific X─P(S)Me─X segment. Our results show that the GAE is more considerable for the justification of the conformational preferences of compounds than the other factors [1-2].