Crystal morphology and their lattice contraction control for the topochemical reaction of bis(phenylethenyl)-dicyanopyrazines

Topochemical photoreaction of bis(phenylethenyl)-dicyanopyrazines (1) was conducted in solution, in the vapor deposited thin film, and in the single crystals. Compound 1 showed the crystal morphology to give the yellow and orange colored crystals. The difference in crystal structures of yellow and orange crystals was confirmed with X-ray crystal analysis which revealed that the orange one was contracted in the crystallographic c-axis by 0.11 Å than that of the yellow one at the same temperature. The physical property and photoreactivity of two crystals were explained with the topochemical control and lattice contraction.