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 Kekul?-structure-based theoretical models. Earlier examples of such anomalous cyclic conjugation were observed in highly strained, non-planar benzenoid systems. Because the molecule of TBCA is perfectly planar and strain-free, its cyclic conjugation pattern could be tested and verified by means of high-level, B3LYP/6- 311+G(d,p), ab initio DFT calculations.