THE EFFECT OF THE METHOXY GROUP ON THE GEOMETRY OF THE BENZENE-RING SUPPORTED BY CRYSTAL-STRUCTURE STUDIES AND AB-INITIO CALCULATIONS - CRYSTAL AND MOLECULAR-STRUCTURE OF 4-(4-METHOXYPHENYL)-2,6-DIPHENYLPYRIDINE AND -METHYL-4-(4-METHOXYPHENYL)-2,6-DIPHENYLPYRIDINIUM PERCHLORATE

Crystal and molecular structures of 4-(4-methoxyphenyl)-2,6-diphenylpy ridine (I) and 1-methyl-4(4-methoxyphenyl)-2,6-diphenyl pyridinium per chlorate (II) are reported, with R=0.052 and 0.070, respectively. The lower precision of II is due to disorder of the perchlorate anion. A g eometrical analysis of 8 p-substituted derivatives of anisole shows th at the methoxy group interacts strongly with the ring via the resonanc e effect. Significant deformations of the exo-cyclic bond angles at Me O-substituted carbon atom are due to steric hinderance between ortho C -H and Me group. Ab initio calculations for anisole are in line with t he observed planar conformation of these systems. The difference in en ergy between the planar and perpendicular conformers is 1.4 kcal/mole at the 6-31G level. The intramolecular interactions between the -OMe group and C-ipso-CorthoH are explored through additional ab initio cal culations. They induce more double character of C-ipso-C-ortho bond, t hereby causing one Kekule structure to be preferred.