Eight-coordinate mono- and dinuclear Dy(iii) complexes containing a rigid equatorial plane and an anisobidentate carboxylate ligand in the axial position: synthesis, structure and magnetism

Abstract

A rigid pentadentate chelating ligand (H₂L) has been utilized to synthesize a series of octacoordinate mononuclear complexes, [Dy(L)(Ph₃PO)(OOCR)] (where R = C₆H₅ (1), C(CH₃)₃ (2), CF₃ (3)) and a dinuclear complex, [Dy₂(L)₂(Ph₃PO)₂{(OOC)₂C₆H₄}] (4) based on the highly anisotropic Dy(III) ion. All the complexes were structurally characterized by single-crystal X-ray diffraction studies. The complexes were formed by the coordination action of the dianionic pentadentate ligand [L]²⁻, one phosphine oxide, and carboxylate ligands. DC and AC magnetic measurements were performed on 1–4. Complexes 1–4 show SMM behaviour, under zero DC field for 1 and 4, and under 500 Oe and 1000 Oe DC fields for 2 and 3 respectively, with thermally activated, Raman, and Raman and quantum tunnelling dominant relaxation mechanisms for 1 and 2, 3 and 4, respectively.