Stabilization of non-standard conformations of the annulene rings in cyclobutadiene-framed [n]annulenes (n = 8, 10, 12, 14) and their beryllium sandwich-like complexes: a quantum chemical study

Abstract

The structures of a series of polycyclic derivatives of [n]annulenes (n = 8, 10, 12, 14) functionalized with peripheral cyclobutadiene rings were studied using the DFT B3LYP/6-311+G(3df,2p) and M062X/6-311+G(3df,2p) methods. The compounds with n = 8 and 10 have the planar and those with n = 12, 14 saddle-shaped conformations of the central rings. Stabilization of non-standard planar forms of the hydrocarbons with central 12- and 14-membered conjugated rings may be achieved through π-complexation of C=C bonds of the cyclobutadiene fragments with beryllium atoms to afford the sandwich-like complexes with circular arrangement of beryllium centers around the perimeter of a ligand.