An octanuclear Schiff-base complex with a Na2Ni6 core: structure, magnetism and DFT calculations

Abstract

The octanuclear Na₂Ni₆ complex (Pr₃NH)[Na₂Ni₆(L)₄(Bza)₅(HBza)(OH)₂(ace)]·Et₂O (1), where Pr₃NH⁺ = the tripropylamonium cation, H₂L = 2-[(E)-(2-hydroxybenzylidene)amino]phenol, HBza = benzoic acid and ace = acetone, was synthesized and characterized by the elemental analysis, FTIR spectroscopy, single crystal X-ray diffraction analysis, magnetic measurements and DFT calculations. All six Ni^II atoms are hexacoordinate with the {NiO₆} or {NiNO₅} chromophores forming two defective dicubane cores. The static magnetic data were fitted to the simplified spin Hamiltonian model which resulted in averaged ferromagnetic and antiferromagnetic exchange parameters J = +5.3 cm⁻¹, and J = −9.2 cm⁻¹, respectively, confirming the predominant role of the antiferromagnetic coupling in 1. The broken symmetry DFT method with various functionals (B3LYP, PBE0, TPPSh and CAM-B3LYP) was used to dissect information about magnetic coupling. As a result, the isotropic exchange parameters (J_ab) derived by the PBE0 or B3LYP functionals seem to be the best to match the experimental magnetic data.