Local aromaticity in benzoand benzocyclobutadieno- annelated phenanthrenes

Abstract

The effects of benzo- and benzocyclobutadieno-(BCBD-)annelation on the local aromaticityćof the central ring (X) of phenanthrene were examined. The local aromaticityćof the ring X was estimated using a graph-theory-based index and two geometrybasedćindices. DFT calculations of phenanthrene congeners showed that many of thesećmolecules are nonplanar, with significant steric strain. All three indices indicate thatćthe effect of benzo-annelation is opposite to that of BCBD-annelation. The deviation ofćsome phenanthrene derivatives from planarity does not influence the effects of annelation.ćThis finding is in accord with some previously reported studies on the dependencećof the aromaticity of the ring(s) on distortion from planarity. © Taylor & Francis Group, LLC.