Synthesis, crystal structures and magnetic properties of nitronyl nitroxide radical-coordinated copper(II) complexes

The coordination compound constructed for nitronyl nitroxide radical NIT-Ph-4-Br and CuII(hfac)2(H2O)2 building blocks (NIT-Ph-4-Br = 2-(4-bromo-phenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, hfac = hexafluoroacetylacetonato) was successfully synthesized. The single-crystal X-ray diffraction analyses indicated that the complexes {(NIT-Ph-4-Br)2[Cu(hfac)2]3} have centrosymmetric five-spin structures consisting of three Cu(II) ions bridged by two nitroxide ligands and that they consist of two types of copper atoms, one with a heavily Jahn–Teller distorted (4 + 2) octahedral coordination (Cuoct) and hfac in trans-positions and the other with square pyramidal five-coordinated (Cupyr) with three hfac oxygen atoms and N–O oxygen atom at the base and the one hfac oxygen atom at the apex. Different geometries of the copper ions are quite important for magnetochemistry. The magnetic susceptibility study of the coordination compound shows strong antiferromagnetic interactions between the metal center and the organic radical.