{[Ln(hfac)3]2[Cu(hfac)2]3(NIT-Pyrim)2(H2O)2} (LnIII = Gd, Ho, Er): Unique Nitronyl Nitroxide Bridged 3d–4f Heterometallic Clusters

Abstract

A series of novel 3d–4f heterometallic complexes involving pyrimidine-substituted nitronyl nitroxide radicals with the formula {[Ln(hfac)3]2[Cu(hfac)2]3(NIT-Pyrim)2(H2O)2} [LnIII = Gd (1), Ho (2), Er (3); NIT-Pyrim = 2-(5-pyrimidinyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide] have been isolated and characterized in terms of structure and magnetism. These 2p–3d–4f compounds consist of CuII3LnIII2 pentanuclear clusters in which two NIT-Pyrim radicals act as µ3 bridges. All compounds display ferromagnetic interactions between the radicals and metal ions. Slow magnetic relaxation was observed in the Ho complex, which represents the first example of a radical–Ho cluster exhibiting magnetic relaxation behavior.