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

The mononuclear complex [Ni(pydc)(pydm)]center dot 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 approximate to -14 cm(-1). This complex displays superparamagnetic behaviour in an applied external field that culminates at B-DC = 0.2 T. Two relaxation processes are evidenced; the faster can be analyzed in terms of the Orbach, direct, and Raman processes yielding U/k(B) = 21.2 (+/- 1.3) K and tau(0) = 3.83 (+/- 1.21) x 10(-7) s. This is the first example of a field-induced single-molecule magnet in the class of hexacoordinate Ni(II) complexes.