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The localized molecular orbitals and energy levels for four typical conjugated six-memberedring systems C_6H_6, C_3N_3H_3, B_3N_3H_6, and (B_3O_6)~(3-) as well as a non-aromatic reference moleculeN_3Cl_6 have been calculated by using Edmiston-Ruedenberg energy localization technique under theCNDO/2 approximation in order to investigate the nature of aromaticity or quasi-aromaticity ofthe six-membered ring systems studied. The contour maps for π-type localized MO’s (LMO) havebeen plotted to illustrate the bonding characteristics of the five ring systems studied. These LMOcalculations show that for all the conjugated six-membered ring systems considered there exists localdelocalization of π-bonds or three-centered and occasionally four-centered two-electron π-bondsin our terminology, and the cooperative effect among these π-bonds leading to the formation ofa closed continuous x-conjugation system around the ring, which is necessary for the creation ofaromaticity in the systems studied. We have been able to discuss the properties of these three-centeredπ-bonds in terms of the constituent atoms and electrons and the relevant orbitals involved.
The localized molecular orbitals and energy levels for four typical conjugated six-membered ring systems C_6H_6, C_3N_3H_3, B_3N_3H_6, and (B_3O_6) ~ (3-) as well as a non-reference moleculeN_3Cl_6 have been calculated by using Edmiston-Ruedenberg energy localization technique under theCNDO / 2 approximation in order to investigate the nature of aromaticity or quasi-aromaticity of the six-membered ring systems studied. The contour maps for π-type localized MO’s (LMO) have bound plotted to illustrate the bonding characteristics of the five ring systems studied These LMOcalculations show that for all the conjugated six-membered ring systems considered there exists localdelocalization of π-bonds or three-centered and occasionally four-centered two-electron π-bonds in our terminology, and the cooperative effect among these π-bonds leading to the formation of a closed continuous x-conjugation system around the ring, which is necessary for the creation ofaromaticity in the systems studie d. We have been able to discuss the properties of these three-centeredπ-bonds in terms of the constituent atoms and electrons and the relevant orbitals involved.