Bond length interrelations in benzenoid hydrocarbons and their heteroatom analogues

The geometries of some benzenoid hydrocarbons and their analogues with XY (XY = BB, BC, BN, CN, and NN) bonds have been determined at the B3LYP/6-311++G∗∗ level of theory. It is shown that the lengths of peripheral XY bonds are strictly correlated with the lengths of their CC counterparts in native hydrocarbons. No correlation of this type is observed for the XY bonds located inside the rings.