Photoisomerizable azobenzene-containing oxacalixarenes

The first examples of photo-responsive azobenzene-containing oxacalixarenes have been synthesized via a 3+1 macrocyclization approach. Introduction of the photoresponsive unit was achieved by using 4-phenylazoresorcinol or (E)-4-(4′-nitrophenylazo)resorcinol as the nucleophilic component in the macrocyclization reaction. These novel macrocycles have been characterized by means of 1D and 2D NMR spectroscopy and DFT calculations (B3LYP/6-31G(d)). According to thermal and photoisomerization studies, tetranitro-oxacalix[4]arenes are less prone to E→Z isomerization than oxacalix[2]arene[2]triazines and, within the two series, p-nitrophenylazo derivatives are more unwilling to isomerize than their phenylazo analogues.