Disassembly Mechanisms and Energetics of Polymetallic Rings and Rotaxanes

Abstract

Understanding the fundamental reactivity of polymetallic complexes is challenging due to the complexity of their structures with many possible bond breaking and forming processes. Here, we apply ion mobility mass spectrometry coupled with density functional theory to investigate the disassembly mechanisms and energetics of a family of heterometallic rings and rotaxanes with the general formula [NH₂RR'][Cr₇MF₈(O₂C^tBu)₁₆] with M = Mn^II, Fe^II, Co^II, Ni^II, Cu^II, Zn^II, Cd^II. Our results show that their stability can be tuned both by altering the d-metal composition in the macrocycle and by the end groups of the secondary ammonium cation [NH₂RR']⁺. Ion mobility probes the conformational landscape of the disassembly process from intact complex to structurally distinct isobaric fragments, providing unique insights to how a given divalent metal tunes the structural dynamics.