A family of lanthanide compounds based on nitronyl nitroxide radicals: synthesis, structure, magnetic and fluorescence properties

Abstract

A series of lanthanide nitronyl nitroxide radical compounds, [Ln(hfac)₃(NITPh-p-N(CH₃)₂)₂]·xC₇H₁₆ (Ln = La (1), Eu (2), Gd (3), Tb (4), Dy (5), Er (6), hfac = hexafluoroacetylacetonate; NITPh-p-N(CH₃)₂ = 4′-dimethylamino-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, x = 2/3 for complexes 1, 2, 3 and 6, and 0 for 4 and 5), have been synthesized and structurally characterized. X-Ray crystallographic analyses show that the structures of the six compounds are similar and all consist of isolated molecules, in which central Ln(III) ions are coordinated to six oxygen atoms from three hexafluoroacetylacetonate ligands and two oxygen atoms from nitronyl nitroxide radicals. Variable-temperature magnetic susceptibility studies reveal ferromagnetic interactions between the Gd(III) ion and nitronyl nitroxide radical in complex 3. Ac magnetic susceptibility measurements of complexes 4 and 5 exhibit frequency-dependent out-of-phase signals, indicating single-molecule magnet (SMM) behavior.