Tetranuclear cobalt(II) and nickel(II) complexes with an unsymmetrical salamo-like ligand: Structural characterization, Hirshfeld analysis and fluorescent properties

Abstract

Two newly designed tetranuclear transition metal(II) complexes, [{Co(L)(μ-OAc)Co(CH3OH)2}2] and [{Ni(L)(DMF)(μ-OAc)Ni}2] derived from an unsymmetrical salamo-like donor-N2O4 ligand (H3L: 6-hydroxy-6′-methoxy-2, 2′-[ethylenediyldioxybis(nitrilomethylidyne)]diphenol) were synthesized and characterized by elemental analysis, FT-IR, UV-vis, fluorescence spectroscopy, X-ray crystallography and Hirshfeld surface analysis. The Co(II) complex includes two fully deprotonated (L)3− moieties, two μ-acetato ligands and four coordinated methanol molecules, bearing a highly symmetrical tetranuclear structure. The terminal Co(II) ions are penta-coordinated and have slightly twisted triangular bipyramidal geometries, and the central Co(II) ions are hexa-coordinated and possess slightly twisted octahedral geometries. The Co(II) complex was self-assembled by adequate intermolecular hydrogen bonding interactions giving rise to an infinite two-dimensional supramolecular structure. The Ni(II) complex adopts a symmetric tetranuclear structure including two fully deprotonated (L)3− units, two coordinated DMF molecules, and two μ-acetato ligands. All the Ni(II) ions are hexa-coordinated and have slightly twisted octahedral geometries. At the same time, the fluorescent properties and Hirshfeld surfaces analyses of the Co(II) and Ni(II) complexes were also investigated in detail.