Synthesis and photochemical study of a supramolecular pseudodimeric complex of 4-styrylpyridinium derivatives

1-(3-Ammoniopropyl)-4-[(E)-2-(3,4-dichlorophenyl)vinyl]pyridinium diperchlorate was synthesized and its crystal structure was studied by X-ray diffraction. The photochemical properties of this compound and its complexation with a 18-crown-6-containing derivative of 4-styrylpyridine were studied by electronic spectroscopy. These compounds form a supramolecular complex (logK = 3.89 in MeCN at an ionic strength of 0.01 mol L–1), in which the styryl chromophores are arranged one above another due to stacking interactions. The complexation activates the cross [2+2] photocycloaddition of styrylpyridine derivatives. A procedure is proposed for the global analysis of spectrophotometric data, which takes into account the effect of the ionic strength of the solution on the observed equilibrium reaction.