NBO technique as a descriptor of aromaticity

A Natural Bond Orbital (NBO) technique has been used as a descriptor of single or double aromaticity in cyclopropenyl, 1,3,5-dehydrophenyl and hexakis (phenylselenyl) benzene cations and their neutral species. A Density Functional Theory (DFT) exchange-correlation (B3LYP) and long-range-corrected (CAM-B3LYP) functionals with different basis sets have been applied. The regularities of the structural and electronic markers have been adopted as aromaticity indicators. The orderly Wiberg Bond Indices (WBIs) of neighbouring atoms and Harmonic Oscillator Model for Aromaticity (HOMA) indices complement these findings. The degree of delocalization, as an influential source of stability, together with steric and electrostatic factors are monitored for the confirmation of aromaticity.