Crystal and molecular structure of 10-substituted 9-anthracenones. Substituent size as the controlling factor for the nonplanarity of the central ring

Abstract

MM2 calculations for a series of 10-R-9-anthracenones demonstrate an increase of the folding of the central ring with increasing size of the substituent. All the substituents considered prefer the pseudoaxial position except fluorine, which prefers the pseudoequatorial orientation. The anthracenone moiety approaches planarity when the size of the substituents approaches the size of the hydrogen atom. The planar conformation for 9-anthracenone is also shown by vibrational frequency calculations to be a true potential energy minimum at the ab initio 3.21G level