Effects of group 14-16 heteroatoms on the aromaticity of benzene at DFT level

Benzene aromaticity and energy gap (ΔEHOMO-LUMO) are compared and contrasted to those of 11 heterobenzenes containing group 14-16 atoms (Si, Ge, Sn, N, P, As, Sb, O+, S+, Se+, and Te+), at B3LYP/6-311++G∗∗ level. Four diverse quantitative aromaticity indices are used: the nucleus independent chemical shifts (NICS), the aromatic stabilization energies (ASE), harmonic oscillator measure of aromaticity (HOMA), and Bird aromaticity index. The aromaticity appears with a general decrease in going from the top to the bottom of the periodic table (columns 14-16). The main exception is thiopyranium for showing more aromaticity than pyranium. Some inconsistencies are found among results of various indices employed.