Classical resonance rule for predicting the stability/instability of fullerene molecules

Abstract

This communication describes a novel criterion, hereafter called the one-third rule, which enables us to judge molecular stability/instability for carbon cages such as fullerene molecules. This rule is based on the concept that the degree of orbital hybridization around each carbon atom (vertex, site) with three-valency can be expressed as a 3-tuple (P₁, P₂, P₃), where P_i are Pauling bond orders around that carbon atom. By means of such 3-tuples and the solid-geometrical concepts, all the carbon atoms of fullerene molecules can be classified as either stable or unstable. A given fullerene molecule is thus said to be either stable if it has stable carbon atoms only or unstable if it has at least one unstable carbon atom. The present paper shows that the one-third rule which is applied to 6 isomers of C₆₀ and 3 isomers of C₇₀ is effective.