Journal of Physical Organic Chemistry vol:18 issue:11 pages:1123-1131
Quantum chemical calculations using molecular orbital (HF) and density functional (B3LYP) methods, h, conjunction with the 6-311 ++G(d,p) basis set, have been applied to investigate the electronic structure of a series of diamino-meta-quinonoid molecules, each containing a six-membered ring coupled with two exocyclic C=O bonds situated in a meta position, along with two amino substituents (NH2 and NH-R). The chemical bonding phenomena in these zwitterions and isomers where one or two hydrogens are transferred from N- to O- are analyzed with the aid of the atoms-in-molecules (AIM) approach. The relative energies between zwitterionic and quinonoid isomers in both neutral and ionized states also have been evaluated. Substituents exert a strong effect that in many cases changes the energy ordering. Copyright (c) 2005 John Wiley & Sons, Ltd.