•Conjugation and steric effects are evaluated as torsion angle changes.•The dominance of conjugation over steric effect makes trans conformer more stable.•The buckling distortions show the competition of sp2 and sp3 hybridization in Si.•The HOMO–LUMO gap is a probe to characterize π-electrons delocalization.•The linear dependence of charge transfer on cos2 φ0 is explained by π-orbitals coupling.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.

The reaction mechanism of Be(3P) with CH4 has been investigated theoretically at the QCISD(T)/6-311++G(d,p)//UB3LYP/6-311G(d) levels. It is shown that the excited Be atom can readily insert into C–H bond of methane without a barrier and the reaction proceeds through the insertion intermediate H–Be–CH3(3A′) followed by three processes, i.e., direct decomposition, rearrangement and intersystem crossing. Five possible reaction channels, yielding organoberyllium compounds BeH, BeCH3, HBeCH2, HBeCH and HBeCH3(1A1), respectively, have been examined. The high reactivity of Be(3P) atom with methane is supposed to be due to small steric hindrance compared with other group 2 and 12 metal atoms. Our results well rationalize the experimental observations.