A family of multi-spin rare-earth complexes based on a triazole nitronyl nitroxide radical: synthesis, structure and magnetic properties

The combination of Ln(III) ions (Gd(III), Tb(III) or Dy(III)) and a triazole nitronyl nitroxide radical (4-Me-3-NITtrz) as spin carriers results in two mononuclear and one binuclear compounds, namely, [Ln(hfac)(3)(4-Me-3-NITtrz)(H(2)O)] (Ln = Gd(1), Tb(2); hfac = hexafluoroacetylacetone; 4-Me-3-NITtrz = 2-[3-(4-methyl-l,2,4-triazolyl)]-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) and [Dy(hfac)(2)(4-Me-3-NITtrz)(2)][Dy(hfac)(4)]·CHCl(3). Compounds 1 and 2 are isostructural and crystallize in the P1̄ space group, whereas compound 3 crystallizes in the P2(1)/n space group. In 1 and 2, the central Ln(III) ions are nine-coordinated (LnNO(8)) in a distorted spherical capped square antiprism geometry (C(4v)) finished by three bischelate hfac anions and one bidentate triazole radical and one aqua molecule. While 3 is a mixed-coordinated binuclear compound with Dy1 in a triangular dodecahedron (D(2d)) coordination sphere and Dy2 in a biaugmented trigonal prism (C(2v)) coordination sphere. Magnetic studies show that compound 2 exhibits field-induced single-molecule magnet (SMM) behavior.