Synthesis, structure, theoretical studies, and fluorescence properties of two multinuclear Cu(II) bis(salamo)-like complexes.

New di- and tetranuclear Cu(II) complexes, [Cu₂(HL)Cl₂(MeOH)]·MeOH·2CH₂Cl₂ (1) and [Cu₄(L)₂(MeOH)₂](NO₃)₂·EtOH (2), have been synthesized from CuCl₂·2H₂O, Cu(NO₃)₂·3H₂O and a symmetric 5-bromosalicylaldehyde-decorated bis(salamo)-like ligand (H₃L, (1E,3E)-2-hydroxy-5-methylisophthalaldehyde O,O-di(2-((((E)-5-bromo-2-hydroxybenzylidene)amino)-oxy)ethyl)dioxime), and characterized by elemental analyses, IR and UV–vis spectra. Single crystal structure analyses showed a dinuclear Cu(II) structure for 1 and a tetranuclear Cu(II) structure for 2. In 1, two Cu(II) ions are on one side of the double N₂O₂ cavities, and the phenol proton in the other cavity is attached. In 2, four Cu(II) ions are located in four N₂O₂ cavities of two fully deprotonated L³⁻ units, giving a centrosymmetric double helix structure. The Hirshfeld surfaces analyses, Interaction Region Indicator (IRI), and DFT computations of H₃L, 1, and 2 were studied. In addition, the electrochemical and fluorescence properties of 1 and 2 were also investigated. [ABSTRACT FROM AUTHOR]