Synthesis, structure, Hirshfeld analysis and fluorescence properties of a new asymmetric salamo-based ligand and its Cu(II) complex involving oxime oxygen coordination

A new asymmetric salamo-based ligand (H2L) was synthesized and upon reaction with Cu(ClO4)(2)an extremely rare dinuclear Cu(II) complex [Cu-2(L)(2)] was formed and characterized by elemental analyses, infrared spectroscopy, UV-vis absorption spectroscopy, X-ray single crystal diffraction and Hirshfeld surface analyses. The Cu(II) complex consists of two Cu(II) ions and two fully deprotonated ligand (L)(2-)units. The Cu(II) is coordinated with the N(2)O(2)cavity (N1, N2, O1 and O4) of L(2-)and the oxime oxygen (O3) of another L(2-)unit to form a uncommon dinuclear structure. The Cu(II) is five-coordinated,tau = 0.02, and has a configuration of slightly twisted tetragonal pyramidal geometry. The comparison between H2L and its Cu(II) complex through Hirshfeld surface analyses shows that the interaction of O-H/H-O is reduced, indicating that deprotonation of phenolic hydroxyl group and the coordination of Cu(II) forms a stable complex. In addition, fluorescence quenching of the Cu(II) complex compared to H2L further confirms the above experimental results.