Molecular Alignment and Photodimerization of 4‘-Chloro-4-stilbenecarboxylic Acid in Hydrotalcite Clays: Bilayer Formation in the Interlayers

It was observed that the photolysis of 4‘-chlorostilbenecarboxylic acid (CSC) in N,N -dimethylformamide (DMF) yielded mainly a syn head-to-head dimer. The molecular alignment in hydrotalcite interlayers has been investigated by electric linear dichroism (ELD) at room temperature in order to clarify the correlation between the photocyclodimerization and the molecular alignment of CSC intercalated in hydrotalcite interlayers in DMF. ELD analysis in combination with X-ray diffraction analysis of this hydrotalcite complex involving CSC revealed the CSC molecules to be intercalated as a double layer, the tilt angle of the molecular plane being ca. 39.4°. The suggested molecular parallel packing model was found to be in good agreement with the stereochemistry of the photodimerization.