Exploring the effects of counterions and solvents on binuclear and tetranuclear Cu(II) oligo(N,O-donor) salamo-based complexes

In this work, a linear acyclic oligo(N,O-donor) salamo-based chelate ligand H4L containing both dioxime and Schiff base functionalities was synthesized. Its various bi-nuclear and tetra-nuclear complexes, [Cu2(HL)(μ-OAc)]·CH3OH (1) and [Cu4(HL)2(EtOH)](ClO4)2·2EtOH (2) were self-assembled via the ligand H4L with stoichiometric quantities of Cu(OAc)2·H2O/Cu(ClO4)2·6H2O in methanol/ethanol, respectively. The bi-nuclear complex 1 consists of a partly deprotonated (HL)3− anion, two Cu(II) atoms, one μ-OAc− counterion. Each Cu(II) atom center is surrounded by a tetragonal cone geometry. However, complex 2 containing four Cu(II) ions, two partially deprotonated (HL)3− anions, and a ligated ethanol molecule, which forms tetranuclear complex 2 containing four and five-coordinated geometries. The structure of complex 2 acquired is unique as shown herein, the different nucleation numbers and geometrical configurations of the resulting crystal structures may be due to the different anions and solvents used in the synthesis process. The binding ratios of the oligo(N,O-donor) ligand to Cu(II) ions were confirmed by UV titration experiments, two of which are consistented with the single-crystal structures. Finally, MEPs, IRI, Hirshfeld surfaces, and intermolecular interactions and reactive sites were analyzed further, the fluorescent properties were explored.