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

Abstract

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)(H₂O)] (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]·CHCl₃. Compounds 1 and 2 are isostructural and crystallize in the P space group, whereas compound 3 crystallizes in the P2₁/n space group. In 1 and 2, the central Ln^III ions are nine-coordinated (LnNO₈) 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.