Investigation of syntheses, structures, theoretical calculations, and fluorescence properties of two N₃O-donor half-salamo-type Cu(II) complexes

The coordination behaviors of asymmetric quinoline-decorated half-salamo-type ligand HL¹ with Cu(NO₃)₂·3H₂O and Cu(OAc)₂·H₂O were studied. Two Cu(II) complexes, [Cu(L¹)(NO₃)]·CH₃CH₂OH (1) and [Cu₂(L²)₂] (2), were isolated and characterized by X-ray crystallography, FTIR, UV–vis, and fluorescence spectroscopies. Structural analyses showed that 1 is a mononuclear species, whereas 2 is a binuclear entity. Spontaneous cleavage along the oxime N-O bond close to quinoline ring of the ligand HL¹ occurred upon reaction with Cu(OAc)₂·H₂O, yielding an unexpected complex 2. Moreover, DFT theoretical calculations and Hirshfeld surfaces analyses of the ligand HL¹ and its corresponding Cu(II) complexes were investigated in detail.