Chiral and Racemic Tetramorphs of 2,6-Di-t-Butylditolylfuchsone

Abstract

The title molecule 4-(α,α-ditolylmethylene)-2,6-di-t-butyl-1,4-benzoquinone (abbreviated as di-t-butylditolylfuchsone and numbered 2-t-Bu) serendipitously afforded four concomitant polymorphs during routine purification by column chromatography in the same solvent elution fraction. Polymorph I crystallized in chiral space group P21. Polymorphs II, III, and IV crystallized in centrosymmetric space groups P21/n, Pbca, and C2/c, respectively. The role of bulky t-Bu groups for crystallization in the chiral space group is discussed for 2,6-ditolyl and 2,6-diphenyl fuchsones. α,α-Diphenylmethylene-2,6-di-t-butyl-1,4-benzoquinone (di-t-butyldiphenylfuchsone, 1-t-Bu) crystallized in P21 (one polymorph) and P21/c (two polymorphs) space groups. Unfavorable steric repulsions due to bulky t-Bu groups result in voids in the crystal structures of centrosymmetric polymorphs II and III. Phase transformation of racemic structure II to III and finally to chiral polymorph I was monitored by thermal microscopy and differenti...