Synthesis, structural characterization, fluorescence properties, and DFT calculations of a novel hetero-hexanuclear [CuII4GdIII2] bis(salamo)-like complex involving bidentate chelating and bridging nitrate groups

A novel hetero-hexanuclear [CuII4GdIII2] complex with a symmetrical bis(salamo)-like tetraoxime ligand (H4L), [{Cu2(L)(MeOH)Gd(NO3)2(μ2-NO3)}2]·2CH3OH was obtained after careful design and synthesis. The structure of the [CuII4GdIII2] complex was adequately characterized by elemental analysis, FTIR, and UV–vis spectroscopy. The [CuII4GdIII2] complex crystallized in the monoclinic system, space group C2/c embraces four CuII ions with two coordination geometries: tetragonal pyramid and octahedron, two GdIII ions with nine coordinated tricapped trigonal prism geometry, two completely deprotonated octadentate (L)4– units, two coordinated methanol molecules, two bidentate bridging nitrate groups (μ2-NO3–), four bidentate chelating nitrate groups and two crystallized methanol molecules. The [CuII4GdIII2] complex ultimately constructs infinite 2D and 3D supramolecular structures via the intermolecular hydrogen bond interactions. Meanwhile, the fluorescence properties of the ligand (H4L) and its [CuII4GdIII2] complex were studied. The electronic structure and stability of the [CuII4GdIII2] complex were proved by density functional theory calculation.