(Fe4L6)-L-II tetrahedral cage 1 undergoes post assembly modification (PAM) via a Diels Alder cycloaddition of the anthracene panels of the cage with tetracyano ethylene (TCNE). The modified cage 2 possesses an enclosed cavity suitable for encapsulation of the fullerene C-60, whereas original cage 1 forms a unique covalent adduct through a Diels Alder cycloaddition of three of its anthracene ligands with C-60. This adduct undergoes further PAM via reaction of the remaining three ligands with TCNE, enabling the isolation of two distinct products depending on the order of addition of C-60 and TCNE. Modified cage 2 was also able to bind an anionic guest, [Co(C2B9H11)(2)](-), which was not encapsulated by the original cage, demonstrating the potential of PAM for tuning the binding properties of supramolecular hosts.