Keeping dysprosium in line: Trinuclear heterometallic MII2DyIII complexes with M=Cd, Co and Cu

Abstract

Four new heterometallic trinuclear essentially linear (“in-line”) MII2DyIII complexes (M=CdII (1), CoII (2), CuII (3, 4) were synthesised using the ligand 3,5-di-tert-butylbenzoic acid (dtbbaH) in a MeCN : iPrOH (1–3) or in a MeOH : iPrOH : DMF (4) mixture. Single crystal structure analyses revealed the formation of [Cd2Dy(dtbba)6(iPrOH)2(H2O)2NO3] ⋅ iPrOH (1), [Co2Dy(dtbba)6(iPrOH)2(H2O)2NO3] ⋅ iPrOH (2), [Cu2Dy(dtbba)6(MeCN)4NO3] ⋅ MeCN (3) and [Cu2Dy(dtbba)6(iPrOH)1.68(DMF)1.32(H2O)NO3] ⋅ 3iPrOH ⋅ H2O (4). The M−Dy−M angles become more acute from (1) to (3) leading to decreased M⋅⋅M distances. The DyIII ions are 8-coordinate with a distorted triangular dodecahedron geometry and a D2d symmetry whereas the geometry of the 5-coordinate terminal MII ions can best be described as either distorted vacant octahedra or as spherical square pyramids with a C4v symmetry. Magnetic susceptibility measurements were performed on (1), (2) and (3) which allows a comparison of the effect of replacing highly anisotropic CoII with the quantum spin of CuII. Both (2) and (3) show effects of ferromagnetic interactions at low temperatures.