Templating photodimerization of stilbazoles with water-soluble calixarenes

Water soluble six and eight membered calixarenes template the dimerization of trans-stilbazoles. In the absence of calixarenes at the concentrations employed stilbazoles mainly isomerize to the coresponding cis isomers. Calixarenes help to localize the olefins and orient them in a specific geometry to yield anti-head-tail dimers. Electrostatic interaction between the sulfonate anion and the pyridinium ion of the olefin and hydrophobic interaction between the olefin and the host cavity are believed to be responsible for the observed selectivity. ¹H NMR spectra provide evidence for complexation but do not suggest the exact structure of the host-guest complex.