LnIII–CoII heterometallic chains based on pyridine substituted nitronyl nitroxides
Four novel nitronyl nitroxide bridged heterometallic one-dimensional chains, [Ln(hfac)3Co(hfac)2(NIT-4py)2] (LnIII = Y 1, Gd 2, Dy 3) and [Dy(hfac)3Co(hfac)2(NIT-3py)2] 4 (hfac = hexafluoroacetylacetonate; NIT-4py = 2-(4-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide; NIT-3py = 2-(3-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide), have been prepared and characterized. Complexes 1–4 exhibit a 1D chain structure in which Ln(hfac)3 and Co(hfac)2 units are linked by pyridine substituted nitronyl nitroxides through the NO groups of the radicals and the nitrogen atoms of pyridine rings. Complexes 1–4 represent the first examples of 2p–3d–4f compounds containing Co(II) ions. The magnetic properties of these compounds were investigated. The magnetic behavior of the Y(III)–Co(II) complex has been analyzed by using an appropriate magnetic model, which indicates an antiferromagnetic interaction between the Co(II) ion and the radical. The ac magnetic susceptibility measurements of compound 4 display slow relaxation of its magnetization.