2-(3-Pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-1-oxy, IM-3Py (1), reacts with copper(II) bis(hexafluoroacetylacetonate), Cu(hfac)(2), to give three complexes. One of them is a centrosymmetric three-spin species, Cu(hfac)(2)(IM-3Py)(2) (4), where two nitroxide ligands ate pyridyl bound to the metal and the spins independent from 300 to 5 K. The two other complexes, [Cu(hfac)(2)](4)(IM-3Py)(2) (alpha-phases, 5, and beta-phases, 6) are six-spin clusters comprising four copper(II) ions linked by two tridentate IM-3Py units. Their molecular structures are almost identical, but they crystallize in different space groups. For both complexes, two octahedral endo metal ions are involved in a cyclic structure and the two others are exocyclic in a trigonal-bipyramidal environment.