Photo-induced self-assembly of Pt(II)-linked rings and cages via the photolabilization of a Pt(II)-py bond

An inert Pt(II)-pyridine bond is considerably labilized upon UV irradiation. On the basis of this phenomenon, kinetically inert Pt(II)-linked coordination rings and cages are formed in high yields from their components by obtaining a kinetically distributed mixture and subsequently equilibrating the mixture into the thermodynamically stable structures upon temporary photolabilization. This method is applicable when the pyridine rings in the ligands are not conjugated with other aromatic rings, in good agreement with DFT calculations that indicate the dependency of the photolability on the pi-conjugation of the ligand frameworks. Interruption of pi-conjugation either by introducing an methylene linker or by twisting the aromatic rings are effective to accomplish the photo-induced self-assembly.