Formation of a Topochemically Photoreactive Mixed Crystal by Grinding and Its Mechanistic Interpretation

Abstract

Abstract A mixed crystal of ethyl and propyl α-cyano-4-[2-(4-pyridyl)ethenyl]cinnamate was formed in the solid state by simple grinding. The mixed crystal formation was ascertained by the change in the X-ray diffraction pattern upon grinding and by 1H NMR and HPLC analyses of the photoproducts. According to several attempts, it was concluded that a mechanical treatment was necessary for the formation of the mixed crystal phase. The kinetic data concerning the analysis of the topochemical photoproducts revealed that the following growth of the mixed crystal phase was triggered by each of the mixed crystal nuclei and that the growth of the mixed crystal phase was accelerated by either thermal annealing or exposure in humidity. During the early stage of mixed crystal growth, the growth rate was nearly proportional to the surface area of the nuclei of the mixed crystal.