Abstract: Four complexes of the general formula[Ni(pfpr)₂]₂NITR·nH₂O, where pfpr=pentafluoropropionate, NITR=2-R-4,4,5,5-tetramethylimidazoline-l-oxyl-3-oxide, and n=2(for R = ph);3(for R = phMe);4(for R = phCl,PhOMe),were synthesized,Thesecomplexes were characterized by elemental analyses,TG-DTA IR,electronic spectra,ESR and molar conductances. The structures of these complexes were discussed.The variable temperature(4-300 K) magnetic susceptibilities of the complexes[Ni(pfpr)₂]₂NITPHCl·4H₂O and [Ni(pfpr)₂]₂NITPhOMe·4H₂O were determined, indicating that the complexes have a magnetic behaviour of trinuclear system Ni(Ⅱ)-Cu(Ⅱ)-Ni(Ⅱ) with irregular spin state. The observed susceptihility data were fitted to those from theoretical magnetic equation,The exchange constants,J,were found to be equal to-152. 8cm^-1and-174.6 cm^-1,respectively,This indicates a stronger antiferromagnetic spin-exchange interaction between the radical and nickel (Ⅱ) ion.

Key words: Nickle pentafluoropropionate, Nitronyl nitroxides, Magnetism