Theoretical study of conformational effect on electronic structure and charge transfer in silabiphenyl system

Conformational effect on electronic structure and charge transfer of silabiphenyl system has been investigated at several different levels of theory. The rotational potential energy curves as a function of torsion angle show that conjugation effect makes the system favor planar structure whereas steric effect facilitates it to prefer perpendicular one. The competition between these two effects results in a gauche and a trans conformer. Full geometric optimization, frequency analysis, and disassociation energy calculation indicate that the characteristic buckling distortion occurs and the trans conformer is more stable than the gauche. Moreover, conjugation and steric effects on geometric parameters, HOMO and LUMO energies, and electron populations of Si atoms have been evaluated and the results provide more aspects to understand these two effects. Furthermore, the linear dependence of charge transfer on the square of the cosine of torsion angle has been observed on the basis of natural charge population analysis and interpreted by effective π-orbitals coupling model. The present study shows possible manipulation on charge transport by changing the conformations in silabiphenyl system.