Steric effects on the Singlet–Triplet Energy Gaps of Seven Membered Ring silylenes, R2C6H6Si

Abstract

With the aim of recognizing the steric effects on the silylenic R2C6H6Si structures, DFT calculations<br />are carried out on 8 structures of R2C6H6Si (where R is hydrogen (H), methyl (Me), isopropyl (i-pro),<br />and tert-butyl (tert-Bu)). These species are at either triplet (t) or singlet (s) states. Singlet–triplet<br />energy separations (<Gt-s) and relative energies for the above structures are acquired at B3LYP/6-<br />31G** levels of theory. The <Gt–s of R2C6H6Si was increased in the order (in kcal/mol): H (23.73) ><br />i-Pr (20.56) > Me (20.32) > t-Bu (15.92).all singlet states of R2C6H6Si, are more stable than their<br />corresponding triplet states. linear correlations are encountered between the LUMO–HOMO energy<br />gaps of the singlet(stable) states of R2C6H6Si compounds, and their corresponding singlet–triplet<br />energy separations are calculated at B3LYP/6-311++G∗∗ level of theory. Other geometrical<br />parameters such as bond angles, dihedral angles, bond lengths, NBO charge at atoms, dipole<br />moments (D), (HOMO), (LUMO), chemical hardness (F), chemical potential (G), electrophilicity (H)<br />and the maximum amount of electronic charge, <Nmax were calculated and discussed.