Photoinduced transformations in single crystals of 1,2-bis(2-[(E)-3-oxo-3-phenylprop-1-enyl]phenoxy)ethane and 1,5-bis(2-[(E)-3-oxo-3-phenylprop-1-enyl]phenoxy)-3-oxapentane

Abstract

Differences in the parameters of pre-organization of chalcone podands to intermolecular photoinduced [2+2] cycloaddition (PCA) in crystals were discovered. As a result of PCA, the chalcone podand with two oxyethylene units forms stereoregular cyclobutane-containing polymer chains over the whole volume of the single crystal. In the case of the chalcone podand with one oxyethylene unit, the PCA reaction in single crystal becomes impossible; however, its mechanical destruction results in the formation of surface layers with stacking dimers. In these layers, photodimerization occurs due to a decrease in topochemical control from the molecular lattice.