Dc magnetic susceptibility data were measured on powdered polycrystalline samples of 1-2 in the T = 300-2.0 K temperature range, in a field of B = 0.1 T (Fig. ). The χT values of 1/2 at 300 K are 4.29/2.49 cm 3 K mol - 1 , both well below the Curie constant expected for 24/8 uncoupled S = ½ ions (9/3 cm 3 K mol -1 for g = 2.00). As the temperature is decreased the value of χT decreases rapidly and reaches a value of 0 cm 3 K mol -1 at T = 15/5 K in both cases. This behaviour is clearly indicative of very strong antiferromagnetic exchange between neighbouring Cu II ions in both 1 and 2, and the presence of well isolated diamagnetic ground states, as corroborated by magnetisation data (Fig. ).