Verifying the modes of cyclic conjugation in tetrabenzo[bc,ef,op,rs] circumanthracene

Abstract

Cyclic conjugation in the empty central ring of tetrabenzo-[bc,ef,op,rs]circumanthracene (TBCA) is stronger than in its neighboring nonempty rings, contradicting the predictions of Kekulé-structure-based theoretical models. Earlier examples of such anomalous cyclic conjugation were observed in highly strained, non-planar benzenoid systems. As the molecule of TBCA is perfectly planar and strain-free, it was possible to test and verify its cyclic conjugation pattern by means of high-level, B3LYP/6-311+G(d,p), ab initio DFT calculations. © 2012 Copyright (CC) SCS.