Hetero-tri-spin [2p-3d-4f] chain compounds based on nitronyl nitroxide lanthanide metallo-ligands: synthesis, structure, and magnetic properties.

Abstract

Employing nitronyl nitroxide lanthanide(III) complexes as metallo-ligands allowed the efficient and highly selective preparation of three series of unprecedented hetero-tri-spin (Cu-Ln-radical) one-dimensional compounds. These 2p-3d-4f spin systems, namely [Ln3Cu(hfac)11(NitPhOAll)4] (Ln(III) = Gd 1Gd, Tb 1Tb, Dy 1Dy; NitPhOAll = 2-(4'-allyloxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide), [Ln3Cu(hfac)11(NitPhOPr)4] (Ln(III) = Gd 2Gd, Tb 2Tb, Dy 2Dy, Ho 2Ho, Yb 2Yb; NitPhOPr = 2-(4'-propoxyphenyl)-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide) and [Ln3Cu(hfac)11(NitPhOBz)4] (Ln(III) = Gd 3Gd, Tb 3Tb, Dy 3Dy; NitPhOBz=2-(4'-benzyloxyphenyl)-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide) involve O-bound nitronyl nitroxide radicals as bridging ligands in chain structures with a [Cu-Nit-Ln-Nit-Ln-Nit-Ln-Nit] repeating unit. The dc magnetic studies show that ferromagnetic metal-radical interactions take place in these hetero-tri-spin chain complexes, these and the next-neighbor interactions have been quantified for the Gd derivatives. Complexes 1Tb and 2Tb exhibit frequency dependence of ac magnetic susceptibilities, indicating single-chain magnet behavior.