Orientation and molecular structure of 1,5 and 1,8 dichloroanthraquinones by PMR in a nematic solution

Abstract

The structures and the order parameters of 1,5 and 1,8 dichloroanthraquinones have been determined from the dipolar couplings between the protons in the nematic solutions. The results show the effect of steric interactions on the molecular structure. The aromatic rings of 1,8 dichloroanthraquinone are in different planes making an angle of 15° while 1,5 dichlo-roanthraqutnone appears to be flat. The two molecules show peculiar differences in orientation. The "in-plane" order parameters of the 1,8 derivative are about equal while the 1,5 derivative has a strongly preferred alignment axis close to the Cl, Cl internuclear axis.