MS of the cage compounds were performed on a Synapt G2 (Waters, Manchester, UK) mass spectrometer using a direct infusion electrospray ionization source (ESI), controlled using Masslynx v4.1 software. All of the scans in the experimental data are for positive ions. Sample 1 was dissolved in acetonitrile at 50 µM. Due to the low solubility of samples 2 -3, they were dissolved in acetonitrile with 20 % DMF at 50 μM. Prior to analysis, instruments were calibrated using a solution of sodium iodide (2 mg/mL) in 50:50 water:isopropanol. Capillary voltages were adjusted between 1.5 and 2.5 kV to optimize spray quality, while the sampling cone and the extraction cone voltages were minimised to reduce breakdown of the assemblies. Source temperature was set at 80 °C. The data were analysed using MassLynx v4.1 software.