A theoretical study of CH...X (X=O, N, S, P and Pi) interactions

Abstract

High-level ab initio calculations at the CCSD(T)/aug-cc-pVTZ//MP2/aug(d,p)-6-311G(d,p) level was employed to study the cooperative CH/pi effects between the pi face of benzene and several modeled saturated hydrocarbons, our study shows that the geometries of these complexes are governed predominantly by electrostatic interaction between the interacting systems. The binding energies are two to three times larger than that of the prototypical methane-benzene complex. The study of substitution effect of heteroatom on the multiple CH/pi interactions indicates that the oxygen and nitrogen substitution have little effect on the geometry and interaction energy. On the other hand, sulfur, phosphorus and silicon substitution strengthen the multiple CH/pi complexes significantly. The study of gauche/trans conformational equilibrium of a series of XCH2CH2Y (X, Y = NMe2, PMe2, OMe and SMe) molecules shows that that intramolcular CHa??a??a??X (X= O, N, S, P) interaction stabilizes the gauche conformation significantly.