Co(II) and Ni(II) bis(salamo)-based tetraoxime complexes: Syntheses, structural characterizations, fluorescence properties, and Hirshfeld analyses

Abstract

Two new asymmetric complexes with the chemical structural formulas [{Co2(L)(μ 2-OH)}{Co2(L)(OAc)(CH3OH)}{Co2(L)(μ 2-OCH3)}{Co2(L)(μ 2-OAc)}]⋅4CH3OH and [Ni2(L)(μ 2-OAc)(CH3OH)]⋅CH2Cl2⋅3CH3OH have been synthesized from cobalt(II) acetate, nickel(II) acetate, and a bis(salamo)-based tetraoxime ligand derived from 3-bromo-5-chlorosalicylicaldehyde and 4-tert-butyl-2,6-diformylphenol, respectively, and characterized by elemental analyses, IR, UV–vis, fluorescence spectra, and single-crystal X-ray diffraction analyses. The Co(II) complex unit cell contained four crystallographically independent and chemically different heterotrinuclear complexes (molecules A, B, C, and D). The crystal structure included eight Co(II) ions, four completely deprotonated ligand (L)3− moieties, one bridging hydroxide, one monodentate acetate, one bridging methoxy, one bidentate chelating acetate, one coordinated methanol, and four crystallization methanol molecules. The Ni(II) complex had a dinuclear structure. The crystal structure of the Ni(II) complex included two Ni(II) ions, one completely deprotonated ligand (L)3−, one bidentate bridging acetate, one coordinated methanol, one crystallized dichloromethane, and three crystallized methanol molecules. Hirshfeld surface analyses showed that the complexes are stable. Furthermore, the fluorescence quenching of the Co(II) and Ni(II) complexes with H3L further confirmed the above experimental results.