Crystal structure of a new biforked mesogen

Abstract

The crystal structure of a biforked mesogen derived from 3,4-dialkyloxyphenyl propanoic acid is described. The molecule crystallizes in the P2₁/c space group with two molecules per unit cell: a = 50·740 (3), b = 8·425 (2), c = 9·250 (1)Å and β = 91·340 (7)˚; the final reliability factor is R = 0·086. Molecules adopt a zig-zag form: the non-aliphatic central moiety is 36·2 A long; the two alkyloxy chains are stretched (ttt) and are approximately parallel to the xy plane; both chains make an angle close to 120° with the central moiety. Molecules make sheets of about 51 Å thickness; the polyaromatic central core makes an angle close to 60° (tilt angle) with the normal to the sheet and is quasi-parallel to the xy plane; interactions between sheets are very weak. Here, we try to given an explanation of the transition between the crystalline arrangement of molecules and the hexagonal symmetry of the mesophase for this compound.