Assembly Of Four 8-Quinolinate-Based Multinuclear Complexes: The Effect Of Substituents On Core Structures And Photoluminescence Properties

Four multinuclear Cd(II) complexes, namely [ Cd-2(L-1)(2)I-2 center dot 2DMSO] (1), [Cd-3(L-2)(6)] (2), [ Cd-4(L-3)(6)Br-2] (3) and [Cd-4(L-4)(6)Br-2 center dot 2DMF] (4), were prepared by the solvothermal reactions of Cd(II) salts with four 8-hydroxyquinoline ligands containing different substituent groups, respectively. The self-assembly behaviors of the cadmium salts and ligands were subsequently investigated using ultraviolet and fluorescence spectra. In the solid state, single-crystal X-ray diffraction analysis showed that complexes 1-4 exhibit an unprecedented structural diversification, and show one binuclear, one trinuclear and two tetranuclear Cd(II) building units, which can be attributed to the different substituent groups in 8-quinolinate ligands. As a result, the four Cd(II) complexes exhibit disparate photoluminescence properties (emission bands, fluorescence lifetimes and quantum yields). This unique capability may provide a useful strategy to tune the structures and optical properties of multinuclear materials, which could be exploited as important components for optoelectronic devices.