Search

Three lanthanide–nitronyl nitroxide radical complexes [Ln(hfac)3(NIT-2Br-4Py)]2 (Ln(III) = Gd (1), Tb (2), Dy (3); hfac = hexafluoroacetylacetonate; NIT-2Br-4Py = 2-(2′-bromo-4′-pyridyl)-(4,4,5,5-tetramethyl-3-oxylimidazoline-1-oxide)) have been synthesized. Single crystal X-ray diffraction analysis reveals that complexes 1–3 are isomorphous in which NIT-2Br-4Py acts as a bridging ligand linking two Ln(III) ions through the nitrogen atom of pyridine ring and the oxygen atom of N O group to form a four-spin system. The magnetic studies show that ferromagnetic coupling interaction between Ln(III) ions and nitronyl nitroxide radical. Moreover, ac measurements show that Tb(III) complex exhibits frequency-dependent signals at low temperature.

One hydroxyl-containing nitronyl nitroxide radical and its three mononuclear tri-spin compounds Ln(hfac)3(NIT-Ph-3-Br-4-OH)2 (Ln = Gd 1,Tb 2, Dy 3, and hfac = hexafluoroacetylacetonate NIT-Ph-3-Br-4-OH = 2-(3′-Br-4′-hydroxyl)-4,4,5,5- tetramethyl-imidazoline-1-oxyl-3-oxide) have been successfully prepared and characterized. Single crystal X-ray analyses show that complexes 1, 2 and 3 are isomorphous, and the center LnIII ions are eight-coordinated. Careful inspection of the structures reveal that short contact between ORadical atoms with phenolic hydroxy was observed, and hydrogen bonding has a significant function in determining the structure. The magnetic studies reveal that the ferromagnetic interactions between Ln–Radical and antiferromagnetic interactions between the intramolecular radicals coexist in these systems. Alternating current (ac) susceptibilities of Tb and Dy complex indicate that there are no obvious frequency dependent out-of-phase signals.