Photoactivated Supramolecular Assembly Using “Caged Chlorophylls” for the Generation of Nanotubular Self-Aggregates Having Controllable Lengths

Living supramolecular polymerization is a breakthrough system to control the size of supramolecular aggregates. Multidimensional (2D or 3D) self-aggregates of chiral and unsymmetric molecules are observed in nature. For instance, a chlorosome, which is the main light-harvesting antenna in green photosynthetic bacteria, possesses tubular structures of chlorophyll pigments with J-type slipped cofacial and circular arrangements. Here, we report size-controllable construction of chlorosome-like aggregates by photoactivated supramolecular assembly of “caged chlorophyll”. The caged chlorophylls, which were nonassembling (inert) species, were illuminated with UV-light to give the active species one by one, and then the resulting active monomers spontaneously assembled to construct tubular self-aggregates. The length of such chlorosome-like aggregate tubes was dependent on the UV-irradiation duration and intensity of UV-light. The photoactivated supramolecular assembly system would be useful for application of (opto)electronic devices such as solar cells and artificial photosynthesis.