In complex 1, the two Cu II ions sit at a distance of ~11.5 Å and even though they are connected by a conjugated organic ligand (L) one would not expect to see any significant magnetic interaction between them. This is reflected in the χT data which is invariant with temperature, and both the susceptibility and magnetisation data can be simultaneously fitted with a simple Curie law that assumes JCu-Cu = 0.0 cm -1 with gCu = 2.095. The susceptibility and magnetisation data for 2 are near identical to those reported in the literature for [ReBr6] 2-salts. 24 This is to be expected since there has been little distortion to its geometry upon encapsulation, as shown in the overlay plots in Figure and Shape analysis (Table ). Thus a simultaneous fit of the susceptibility and magnetisation data affords gRe = 1.832, DRe = +21.9 cm -1 , in agreement with both previously published experimental 24 and theoretical values. In order to the fit the data for 3, the gCu, gRe and DRe from the fits of compounds 1 and 2 were fixed, and only the JCu-Re interaction allowed to vary. A simultaneous fit of the susceptibility and magnetisation data to spin-Hamiltonian (1) afforded JCu-Re = -0.45 cm -1 . The data cannot be fitted without including exchange between the Cu and Re metal ions. Thus, the experimental magnetic data suggests: (a) there is no magnetic interaction between the Cu II centres (at least for the sensitivity of a SQUID magnetometer). (b) There is a small but finite antiferromagnetic interaction between the Cu II -Re IV ions. (c) Analogous DRe values to previously published Re IV metal salts are observed for the encapsulated ReBr6 2-ions, due to retention of analogous/non-distorted structures. In order to probe these details further, we now turn to theory.