Direct current magnetic susceptibility (χ) and magnetisation (M) data for 1-3 were measured in the T = 270-2 K, B = 0.1 T and T = 2-7 K, B = 0.5-5.0 T temperature and field ranges, respectively. These are plotted as the χT product versus T and M versus B in Figure . For the quantitative interpretation of the magnetic properties of 1-3 we used spin-Hamiltonian (1):