[2 + 2]-Photocycloaddition reaction of self-assembled crown-containing 2-styrylpyridinium perchlorate in a solid state

The dimer assembly of crown ether styrylpyridinium perchlorates (CSP) in solid state and MeCN solution were studied. The obtained data in solid state allowed us to conclude that molecules spontaneously form dimeric complexes. The dimeric complex is stable due to dipole interaction between crown ether donor substitutor of one molecule and the acceptor pyridinium residue of the other one. Irradiation of the dimer complex leads to regio- and stereoselective [2 + 2]-cycloaddition, giving only one cyclobutane isomer. The formation of dimers in solution has not been found. The irradiation of MeCN solution of CSP molecules resulted in the reversible E–Z isomerization.