Clar model modified for nanographenes

Abstract

The empirical Clar model describes the π-electronic configurations for polycyclic aromatic hydrocarbons with closed-shell singlet ground states. However, it is not applicable to nanographenes (NGs), which usually have open-shell ground states. To model the π-electronic configurations of NGs, a new structural unit, radical half-sextet, was introduced. The modified Clar model can profoundly depict the π-electronic configurations for both nonmagnetic and magnetic NGs and thus can be used as the general model for NGs. The new model can precisely predict the favorable reaction patterns for NGs and can profoundly explain the already-known reactions of NGs.