A polynuclear and two dinuclear copper(II) Schiff base complexes: Synthesis, characterization, self-assembly, magnetic property and DFT study

Three elongated (4+1) square pyramidal copper(II) complexes, [Cu2(L)2(μ1,1-N3)2]⋅H2O (1), [Cu2(L)2(μ1,1-NCO)2] (2) and [Cu(L)(μ1,5-dca)]n (3) [HL = 1((2-(methylamino)ethylimino)methyl)naphthalen-2-ol and dca = dicyanamide], have been synthesized using a tridentate N2O donor Schiff base ligand (HL) and characterized. Complexes 1 and 2 are centrosymmetric dimers in which copper(II) centres are connected by asymmetric double end on pseudohalide bridges. Complex 3 features a 1D zigzag chain in which copper(II) centres are connected by end to end dca bridges. Variable temperature (2-300K) magnetic susceptibility measurements indicate the presence of antiferromagnetic exchange coupling between copper(II) centres in complexes 1 (J = -2.313 cm-1) and 3 (J = -0.344 cm-1), whereas complex 2 shows ferromagnetic exchange coupling between copper(II) centres (J = 0.513 cm-1). DFT calculations also corroborate the data. The fluid solution EPR spectra recorded at 293 K are typical of copper(II) species. Significant supramolecular interactions are explored using high level DFT calculations (BP86-D3/def2-TZVP) and characterized by Bader’s theory of “atoms-in-molecules”.