Covalent isoresonance

Two molecular species are defined to be isoresonant if each have like numbe rs of the same (type of) bonds and there is an isomorphism between superpos itions of pairs of Kekule structures giving equivalent interaction patterns (as appear in Hamiltonian matrices). Thus a close physico-chemical corresp ondence follows, as predicted by a variety of semiempirical quantum-chemica l models, and thence presumably for corresponding molecules. Notably simple structural criteria sufficient for isoresonance are found.