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

Abstract

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=−2.313cm−1) and 3 (J=−0.344cm−1), whereas complex 2 shows ferromagnetic exchange coupling between copper(II) centres (J=0.513cm−1). DFT calculations also corroborate the data. The fluid solution EPR spectra recorded at 293K 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”.