Photocontrol of the catalytic activity of a beta-cyclodextrin bearing azobenzene and histidine moieties as a pendant group

An azobenzene group was linked to beta -cyclodextrin via a histidine spacer (1) to produce a photoresponsive catalyst. The ester hydrolysis of p-nitro phenyl acetate, Boc-L-alanine-p-nitrophenyl ester and Boc-D-alanine-p-nitro penyl ester was examined in the presence of trans-1 or cis-1. In the case o f cis-1, the cyclodextrin cavity was used as the substrate binding site dur ing imidazole-catalyzed ester hydrolysis. This was not possible in the case of trans-1 due to the inclusion of the trans-azo-benzene moiety in the cyc lodextrin cavity. Consequently, the catalytic mechanism switches in an on-o ff fashion on UV irradiation, associated with the conversion of the azobenz ene moiety of 1 from trans to cis.