Two tri-spin complexes based on gadolinium and nitronyl nitroxide radicals: Structure and ferromagnetic interactions

Three Radical-Ln(III)-Radical complexes based on nitronyl nitroxide radicals have been synthesized, structurally and magnetically characterized: [Gd(hfac)(3)(NITPhOEt)(2)] (1) (hfac=hexafluoroacetylacetonate, and NITPhOEt=4'-ethoxy-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide), [Gd(hfac)(3) (NITPhOCH2Ph)(2)] (2) (NITPhOCH2Ph = 4'-benzyloxy-pheny1-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) and [Lu(hfac)(3)(NITPhOCH2Ph)(2)] (3). The X-ray crystal structure analyses show that the structures of the three compounds are similar and all consist of the isolated molecules, in which central ions Gd-III or Lu-III are coordinated by six oxygen atoms from three hfac and two oxygen atoms from nitronyl radicals. The magnetic studies show that in both of the two Gel complexes, there are ferromagnetic Gd-III-Rad interactions and antiferro-magnetic Rad-Rad interactions in the molecules (with J(Rad-Gd)=0.27 cm(-1), 2.97 cm(-1) for 1: and J(Rad-Gd)=0.62 cm(-1), j(Rad-Rad)=7.01 cm(-1) for 2). An analogous complex of [Lu(hfac)(3) (NITPhOCH2Ph)(2)] (3) containing diamagnetic Lu-III ions has also been introduced for further demonstrating the nature of magnetic coupling between radicals. (C) 2010 Elsevier Inc. All rights reserved.