**Appendix A**

### *Crystallographic Data and Special Refinement Details*

**Crystal data for 1:** C139H149Cu4N9O36, M = 2775.82, clear green block, 0.02 × 0.01 × 0.01 mm3, orthorhombic, space group C2221, a = 17.052(3) Å, b = 27.160(5) Å, c = 37.010(7) Å, V = 17,140(6) Å3, Z = 4, Dc = 1.076 g/cm3, F000 = 5800, ADSC Quantum 210r, synchrotron radiation (MX1, Australian Synchrotron), λ = 0.7108 Å, T = 100.0K, 2θmax = 52.9◦, 45,853 reflections collected, 14,407 unique (Rint = 0.1457). Final GooF = 1.029, R1 = 0.0861, wR2 = 0.2282, R indices based on 7756 reflections with I > 2σ(I) (refinement on F2), 884 parameters, 178 restraints. Lp and absorption corrections applied, μ = 0.554 mm<sup>−</sup>1.

Data for compound **1** were treated using the SQUEEZE routine of PLATON, finding two large voids per unit cell and several smaller pockets. Density accounting for 292 e<sup>−</sup> was located per cage complex. This tentatively accounts for 15 H2O and 3.5 DMF molecules, more than is found by TGA, although solvent is likely lost in handling and transit. A number of restraints were required for bond lengths and displacement elipsoids, primarily those associated with the iosbutyl chains and disordered solvent sites, as shown in the information embedded in CIF file.

**Crystal data for 2:** C146H124Co8N22O72, M = 3810.10, blue plate, 0.16 × 0.10 × 0.04 mm3, orthorhombic, space group P21212, <sup>a</sup>=35.489(7) Å, b=21.851(4) Å, <sup>c</sup>=25.061(5) Å, V =19,434(7) Å3, Z=4, Dc =1.302 g/cm3, F000 = 7784, ADSC Quantum 210r, synchrotron radiation (MX1, Australian Synchrotron), λ = 0.7108 Å, T = 100.0K, 2θmax = 50.0◦, 125,332 reflections collected, 34,118 unique (Rint = 0.0826). Final GooF = 1.023, R1 = 0.0859, wR2 = 0.2263, R indices based on 27,536 reflections with I > 2σ(I) (refinement on F2), 2356 parameters, 54 restraints. Lp and absorption corrections applied, μ = 0.753 mm<sup>−</sup>1.

The structural model contains significant disorder at the terminal positions of the complexes, and the data were treated using SQUEEZE, due to large spaces between the complexes where no model could be applied. However, no restraints of any kind (other than some restraints for disordered DABCO ligands) were applied to the refinement, and the structure is reported in an unadulterated form. All atoms, other than those associated with the minor components of the disorder, were located and freely refined with anisotropic models. No hydrogen atoms were modelled on the aqua ligands, but these are included in the molecular formula. Some large displacement parameters remain in the model, indicative of disorder in the ligands that could not be modelled. The final refinement has a non-zero Flack parameter, 0.088 (7), which is likely a result of slightly low quality data and large areas of disorder in the model.

The complex containing atoms Co1–Co4 contains three disordered Co positions at the ends, refined with 50:30:20 occupancies by means of equalizing the μiso averaged displacement parameters. There is some evidence of a very minor fourth position (Q peak of apparent Co site < 2 e<sup>−</sup>) for which modelling was not attempted. The aqua ligands were located for the major occupancy site and refined isotropically; those belonging to the minor occupancy positions could not be located. Both DABCO ligands contained disorder that was modelled with fixed 50:50 occupancies.

The complex containing atoms Co5–Co8 contains two disordered Co positions at the ends, refined with 70:30 occupancies by means of equalizing the μiso averaged displacement parameters. Aqua ligands to complete the octahedral coordination sphere were all located for the major component (O only, isotropic model). The central DABCO ligand of the dumbbell contains disorder with two C2H4 groups modelled with fixed 50:50 occupancies, and one C2H4 group is modelled with large displacement parameters, as a disordered model could not be satisfactorily refined. Two carboxylate oxygen atoms (O44 and O52) are modelled as disordered (30:70) in line with being either coordinated to the minor occupancy cobalt position or not.
