Clay-inclusion photocyclodimerization : intercalation and migration of stilbazolium ions

Abstract

Photocyclodimerization and the emissive properties of 4-[2-(p-substituted phenyl)ethenyl]pyridinium ions (stilbazolium ions)(1) intercalated between clay interlayer have been studied in order to clarify the intercalation and mobility of the ions. A statistical product ratio of homo- and cross-bred cyclodimers was observed in the irradiation of an equimolar co-intercalated mixture of 4-[2-(p-tolyl)ethenyl](1b) and 4-[2-(p-cyanophenyl)ethenyl]-pyridinium chlorides (1c). In contrast, when 1b and 1c were intercalated separately, the homodimers were formed predominantly, and the cross : homo ratios increased with increasing adsorption. This indicates that the molecular diffusion of stilbazolium ions between clay particles is much slower, as was also shown by a quenching study of the excimer fluorescence of 1b by 1c.