A loop chain and a three-dimensional network assembled from a multi-dentate nitronyl nitroxide radical and M(hfac)2 (M = CoII, CuII)

Abstract

A multi-dentate nitronyl nitroxide radical Nit-Ph-3,5-bIm (Nit-Ph-3,5-bIm = 2-[3,5-bis(1-imidazole)-phenyl]-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) reacted with Co(hfac)₂·2H₂O or Cu(hfac)₂ to yield two novel 3d-radical complexes {[Co(hfac)₂]₂(Nit-Ph-3,5-bIm)}_n1 and {[Cu(hfac)₂]₇(Nit-Ph-3,5-bIm)₃}_n2 (hfac⁻ = hexafluoroacetylacetonate). In both compounds, the Nit-Ph-3,5-bIm radical ligand behaves as a tetradentate ligand to link four M(hfac)₂ units in a μ₄–η¹:η¹:η¹:η¹-coordination mode via its two NO groups and two N atoms of imidazole, generating a unique loop chain for 1 and a three-dimensional framework for 2. The magnetic studies revealed a strong antiferromagnetic Co–ON exchange interaction in 1 while a ferromagnetic Cu–ON interaction is observed in 2. The dc magnetic behaviors of two complexes are analyzed by means of appropriate magnetic models. Furthermore, ac magnetic susceptibilities of the Co complex reveal slow relaxation of magnetization.