Ab initio study of the structures and dynamic stereochemistry of biaryls

Abstract

The static and dynamic stereochemistry of biphenyl ( 1), 1-phenylnaphthalene ( 2), 1-phenylanthracene ( 3), 9-phenylanthracene ( 4), 1,1′-binaphthyl ( 5), 1,1′-naphthylanthracene ( 6), 1,9′-naphtylantracene ( 7), 1,1′-bianthryl ( 8), 9,9′-bianthryl ( 9) and 1,9′-bianthryl ( 10) were examined using ab initio molecular orbital (MO) and the Becke, Lee, Yong and Parr density functional (B3LYP) methods. The structure of the ground states, the activation energies for rotation about the σ-bonds of compounds 1– 10 and the nature of deformation of aromatic rings in the equilibrium structures and saddle point geometries were also investigated. Studies on the HF/6-31G*//Hf/3-21G, MP2/6-31G*//HF/3-21G and B3LYP/6-31G*//HF/3-21G levels of theory confirm that compounds 5, 6 and 8 should racemize preferably the anti path, (with about 9 kcal mol −1 lower energy than the syn path). However, the resulted racemization energy for compound 5 through the syn path is found to contradict the previously reported semi-empirical calculations.