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

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