Mononuclear lanthanide complexes assembled from a tridentate NNO donor ligand: design of a DyIII single-ion magnet

The reaction of a tridentate NNO donor ligand, 4-nitro-2-((2-(pyridine-2-yl)hydrazono)methyl)phenol (HL) with lanthanide(iii) nitrates in the presence of triethylamine afforded a new family of neutral mononuclear Ln(III) complexes [Ln(NO3)(L)(2)(HOCH3)] (Ln = Gd; (1) Tb; (2), Dy; (3), and Ho (4). The mononuclear complexes were structurally characterized by single crystal X-ray diffraction studies which revealed a spherical tricapped trigonal prism geometry with a pseudo D-3h symmetry around the Ln(III) centre. Static (dc) and dynamic (ac) magnetic studies have been performed on these complexes. Field-induced single-ion magnet behaviour was observed in the Dy-III analogue with an effective energy barrier and an pre-exponential factor of /k(B) = 68(2) K and (0) = 1.8 x 10(-7) s, respectively.