New insight into two penta-coordinated multinuclear copper(II) single-armed salamo-based complexes

Abstract

With the reactions of a single-armed salamo-based ligand H3L and two kinds of copper(II) salts (Cu(OAc)2·H2O or CuCl2·2H2O) in mixed organic solvents, respectively, two penta-coordinated Cu(II) complexes [Cu2(L)(µ-OAc)]·MeOH (1) and [Cu4(L)2Cl2]·EtOH·CH2Cl2 (2) have been successfully constructed. The precise structures of the two Cu(II) complexes obtained by solvent evaporation method are measured by single crystal X-ray diffraction analyses. The di-nuclear complex 1 crystallizes in triclinic space group P-1, where the main structure is compose of two Cu(II) atoms, one completely deprotonated ligand (L)3− unit, one bridged μ-OAc− counter-anion and one crystallized methanol molecule. The tetra-nuclear complex 2 with an inversion center crystallizes in the same space group as 1 and contains four Cu(II) atoms, two fully deprotonated salamo-based ligand (L)3− units, two bridged Cl− counter-anions, one crystallized dichloromethane and one ethanol molecules. Compared to preceding complexes based on other single-armed salamo-based ligands, the structure of complex 2 reported in this work is unique and has never been found in previous literatures. All of Cu(II) atoms in complexes 1 and 2 are penta-coordinated with the geometries of distorted tetragonal pyramid, and the τ5 value of all Cu(II) atoms have been calculated and all results are less than 0.5. Hirshfeld surfaces analyses of complexes 1 and 2 have been established to explain the interactions of crystal structures, and the corresponding two-dimensional (2D) fingerprint plots have been carried out to quantify the intermolecular interactions. In addition, fluorescence properties of complexes 1 and 2 have been investigated.