Hierarchical organization of spherical assembly with reversibly photocontrollable cross-links.

A ternary photocontrollable assembly was hierarchically constructed by the "orthogonal" host-guest interaction of different types of cyclodextrins toward the porphyrin and azobenzene. Spectroscopic titrations and microscopic investigations demonstrate that the inclusion complex of azobenzene modified water-soluble porphyrin (1) with phthalocyanine-grafted permethyl β-cyclodextrins (2) could be reversibly cross-linked to relatively larger nanospheres with naphthyl bridged bis(α-cyclodextrin)s (3). Moreover, the large-sized spheres (1·2·3) could be disassembled and switched to small-sized complex (1·2) upon the photoinduced isomerization of an azophenyl group.