MOLECULAR-STRUCTURES AND PACKING ARRANGEMENTS OF 5 2,5-BIS(ARYL-2-VINYL)-1,4-DIMETHOXYBENZENE DERIVATIVES

The crystal and molecular structures of five 2,5-bis(aryl-2-vinyl)-1,4-dimethoxybenzene derivatives 1a-1e were determined by X-ray diffraction with respect to topochemical aspects. We found three types of packing arrangements: (1) alpha-type packing with 7 angstrom stacking axes, (2) beta-type packing with 4 angstrom stacking axes and (3) a third intermediate packing type. The intermolecular distances between the vinylic double bonds of all derivatives exceed the limits of 4 angstrom in the crystals. Therefore photochemical [2 + 2]cycloadditions were not observed in the crystals of these compounds. A correlation between the inclination angle of the molecular plane to the stacking axis and the separation between potentially reactive double bonds was detected.