Density functional theory study of the magnetic coupling interaction in a series of binuclear oxalate complexes

Magnetic couplings in oxalate-bridged binuclear complexes, namely five isomers of [(VO)(2)(ox)(SCN)(6)](4-), trans-(equatorial, equatorial), cis-(equatorial, equatorial), trans-(axial, axial), cis-(axial, axial), and (axial, equatorial), as well as [Cr-2(ox)(SCN)(8)](4-), [Fe-2(ox)(SCN)(8)](4-), [CrFe(ox)(SCN)(8)](4-), [Fe-2(ox)(5)](4-), [Cr-2(ox)(5)](4-), [Ni-2(ox)(5)](6-), and [Cu-2(ox)(C12H8N2)(2)](2+), were calculated with the broken symmetry approach. Predominant antiferromagnetic coupling is found in almost all investigated complexes, except in [CrFe(ox)(SCN)(8)](4-). The best agreement with experimental values for the exchange coupling constants were obtained at the B3LYP level of theory, whereas the non-hybrid functionals gave the best trend for the investigated vanadium complexes. The linear relationship between coupling constant and (epsilon (2) - epsilon (1))(2) as well as linear dependence of J and the square of overlap integral of magnetic orbitals was estimated.