A mononuclear Ni(ii) complex: a field induced single-molecule magnet showing two slow relaxation processes

The mononuclear complex [Ni(pydc)(pydm)]·H2O, pyridine-2,6-dicarboxylato-2,6-bis(hydroxymethyl)pyridine nickel(ii) monohydrate, features a highly axially compressed pseudo-octahedral chromophore with significant rhombic contribution that is responsible for the sizable magnetic anisotropy of the Ni(ii) ion, D/hc≈-14 cm(-1). This complex displays superparamagnetic behaviour in an applied external field that culminates at BDC = 0.2 T. Two relaxation processes are evidenced; the faster can be analyzed in terms of the Orbach, direct, and Raman processes yielding U/kB = 21.2 (±1.3) K and τ0 = 3.83 (±1.21) × 10(-7) s. This is the first example of a field-induced single-molecule magnet in the class of hexacoordinate Ni(ii) complexes.