Synthesis, structures and luminescence properties of 3d-4f heterometallic-organic frameworks (HMOFs) constructed from different copper halide clusters

Four novel 3d-4f heterometallic-organic frameworks (HMOFs), namely [Gd-2(Cu2I2)(C6H4NO2)(6)(C3H7NO)(H2O)]center dot(C3H7NO) (1), [Gd-2(Cu4I4)(C6H4NO2)(6)(C3H7NO)(2)] (2), [Gd-2(Cu6I6)(C12H8NO2)(6)(C2H6O)(2)(H2O)(2)] (3) and [Gd-2(Cu8I8)(C12H8NO2)(6)(H2O)(4)]center dot 5(C4H8O2) (4), have been solvothermally synthesized and characterized. The four compounds incorporate Cu2I2, Cu4I4, Cu6I6 and Cu8I8 clusters in three-dimensional frameworks, respectively, and the influence of Ln(3+) ions, copper halide clusters and ligands on the construction of the structures has been analyzed. The four compounds display four different emission colours. Interestingly, compound 3 responds to external mechanical force. After grinding, the fluorescence has been obviously quenched. Compound 4 displays a reversible luminescence behavior, accompanying the removal and recovery of the guest molecules in the channel.