Broken symmetry approach and density functional theory investigation on hetero-spin system consisting of copper(II) and aminoxyl radicals: Comparison and reliability of different basis sets approaches

The combination of different exchange correlation functionals and mixed basis sets was proposed to determine the exchange coupling constant (J) for complex consisting of bis(hexafluoroacetylacetonato)copper(II) [Cu(hfac)2] and 4- or 3-(N-oxyl-tert-butylamino)pyridine (4NOPy or 3NOPy) denoted as [Cu(hfac)2(4NOPy)2] (1) or [Cu(hfac)2(3NOPy)2] (2). Comparing with available experimental data and our previous theoretical results, we have shown that the PBE and PBE0 functionals with the CEP-121G/6-31+G(d,p) and LanL2DZ/6-311G(d) basis sets are the best approaches for determining J values for complexes 1 and 2, respectively.