Anion-controlled structures and luminescent properties of three Cd(II) complexes assembled by a 2-substituted 8-hydroxyquinoline ligand

This work reports the self-assembly of three cadmium complexes 1-3 from one 2-substituted 8-hydroxyquinoline ligand (HL). The skeleton exhibits an unprecedented structural diversification and fabricates one mononuclear and two different tetranuclear Cd(II) building units in response to the counteranions NO3-, OAc- and I-, respectively. The self-assembly behavior of the cadmium salts and the HL in MeOH was subsequently investigated using UV-vis spectroscopy. In the solid state, the supramolecular structures of 1-3 feature unique helical chains or a 3D network via non-covalent interactions, such as pi center dot center dot center dot pi stacking, C-H center dot center dot center dot pi, hydrogen bonding and halogen-related interactions. As a result, the three Cd(II) complexes exhibit disparate photophysical properties. This unique capability may provide a useful strategy to tune the optical properties of multinuclear materials, which could be exploited as important components for optoelectronic devices.