Synthesis and magnetic properties of nickel(II) complexes with the nitronyl nitroxides

Four novel complexes of nickel(II), Ni(tfac)2(NITPa)2 (1), Ni(tfac)2(NITPhNO2)2 (2), Ni(pfpr)2(NITPa)2 (3) and Ni(pfpr)2(NITPhNO2)2 (4), [tfac=trifluoro- acetato, NITPa=2-(3,4-methylenedioxyphenyl)-4,4,5, 5-tetramethylimidazoline-1-oxy-3-oxid, NITPhNO2= 2-(3-nitrophenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxid, pfpr=pentafluoropropionato], have been prepared and characterized by elemental analysis, i.r., and electronic spectra, and molar conductances. The temperature dependence of the magnetic susceptibility for complexes (1) and (3) was measured (4–300K). The observed data were successfully simulated giving the exchange integral J=−1.48cm−1 for (1) and J=−1.25cm−1 for (3). These results indicate a weak antiferromagnetic spin exchange interaction between nickel(II) ion and the radicals.