Light-Controlled Destruction and Assembly: Switching between Two Differently Composed Cage-Type Complexes

Abstract

We report on two regioisomeric, diazocine ligands 1 and 2 that can both be photoswitched between the E- and Z-configurations with violet and green light. The self-assembly of the four species (1-Z, 1-E, 2-Z, 2-E) with CoII ions was investigated upon changing the coordination vectors as a function of the ligand configuration (E vs Z) and regioisomer (1 vs 2). With 1-Z, Co2(1-Z)3 was self-assembled, while a mixture of ill-defined species (oligomers) was observed with 2-Z. Upon photoswitching with 385 nm to the E configurations, the opposite was observed with 1-E forming oligomers and 2-E forming Co2(2-E)3. Light-controlled dis/assembly was demonstrated in a ligand competition experiment with sub-stoichiometric amounts of CoII ions; alternating irradiation with violet and green light resulted in the reversible transformation between Co2(1-Z)3 and Co2(2-E)3 over multiple cycles without significant fatigue by photoswitching.