Post-assembly Modification of Kinetically Metastable Fe^II₂L₃ Triple Helicates

We report the covalent post-assembly modification of kinetically metastable amine-bearing FeII2L3 triple helicates via acylation and azidation. Covalent modification of the metastable helicates prevented their reorganization to the thermodynamically favored FeII4L4 tetrahedral cages, thus trapping the system at the non-equilibrium helicate structure. This functionalization strategy also conveniently provides access to a higher-order tris­(porphyrinatoruthenium)–helicate complex that would be difficult to prepare by de novo ligand synthesis.