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.

A mononuclear hexacoordinate Cu(II) complex shows a field induced slow magnetic relaxation that is not facilitated by an energy barrier to spin reversal due to the zero-field splitting. Two relaxation channels were found: the magnetic field strongly supports the low-frequency relaxation path with a relaxation time as long as τ = 0.8 s at T = 1.9 K and B = 1.5 T. The mechanism of the relaxation at low temperature involves the dominant Raman process for this S = 1/2 spin system along with a temperature-independent term belonging to a quantum tunneling.

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The synthesis and characterization (elemental analysis, IR, electronic and EPR spectra as well as magnetization measurements over the temperature range 1.8 K-300 K) of solid complex [Cu(5-MeOsal) 2 (µ-nia)(H 2 O)] 2 (1; 5-MeOsal = 5-methoxysalicylate, nia = nicotinamide) is reported together with the crystal structure. In blue-green complex 1, two Cu(5-MeOsal) 2 (H 2 O) units are held together by a pair of bidentate nonchelating nicotinamide ligands, which form a (CuNC 3 O) 2 ring. Each Cu atom adopts a distorted squarepyramidal geometry. The oxygen atoms from two unidentate 5-MeOsal anions occupy the trans position, a water molecule and the pyridine N atom of nicotinamide build the basal plane and a carboxamide O atom occupies the apical position. The separation between two Cu atoms within the centrosymmetric dimer is 6.940(2) Å. The dimeric units are self-