Two new one-dimensional nitronyl nitroxide radical-Ln III chain complexes, [Gd(hfac) 3 (NIT-I)] (1) and [Tb(hfac) 3 (NIT-I)] (2) (hfac = hexafluoroacetylacetonate; NIT-I = 2-iodo-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide), have been synthesized. Both complexes have linear chain structures in which the NIT-I radical ligands link the Ln(hfac) 3 units
[a]1320 through the oxygen atoms of the nitronyl nitroxide groups. Direct-current magnetic studies show that the Gd complex is paramagnetic above 2.0 K, whereas the Tb complex exhibits 3D antiferromagnetic ordering with T N = 4.0 K. Furthermore, complex 2 possesses frequency-dependent ac magnetic susceptibilities, which suggests slow magnetic relaxation.which is ferromagnetic with Tb and Dy. Note that SCM behavior can still occur in the ferri-or antiferromagnetically ordered phase of spin chains, for example, Co II -nitronyl nitroxide radical chains, [5] Mn III Ni II chain compounds, [6] and Co II chains embedded in 2D systems. [7] Very recently, we observed such behavior in a one-dimensional lanthanideradical system. [8] We have been very interested in exploring the structuralmagnetic relationships in one-dimensional lanthanidenitronyl nitroxide radical systems. We are currently working with nitronyl nitroxide radicals with various substitutions to tune the distances between spin chains. Thus, we chose the nitronyl nitroxide radical NIT-I (NIT-I = 2-iodo-4,4,5,5-tetramethylimidazolin-1-oxyl 3-oxide), which has small substituents, to construct a new one-dimensional lanthanide-radical system. Two novel lanthanide-nitronyl nitroxide 1D compounds, namely [Ln(hfac) 3 (NIT-I)] (Ln = Gd 1, Tb 2; hfac = hexafluoroacetylacetonate), were obtained. Magnetic studies showed that an antiferromagnetic interaction dominates in complex 1, whereas in complex 2 there coexists metamagnetism, 3D antiferromagnetic (AF) ordering, and slow magnetic relaxation, which is a rare example of slow magnetic dynamics in an AF ordered phase.
Results and Discussion
Crystal StructureSingle-crystal X-ray diffraction analyses revealed that complexes 1 and 2 are isomorphous, both crystallizing in the monoclinic space group P2 1 /n, and consist of linear chains. The atom-labeling scheme for the crystal structure