Conductive Organometallic Polymers from Soluble Superatom Ions

Superatomic crystals comprising ligand-capped, metal chalcogenide clusters and fullerenes are modular materials that exhibit enhanced electronic, magnetic, and thermal conductivity properties. We find that neutral, M₄S₄ (M = Fe, Co) clusters stabilized with N-heterocyclic carbenes (NHCs) can transfer charge to C₆₀ fullerene to form binary superatomic crystals. Notably, these compounds are soluble in various organic solvents, allowing their properties to be investigated in solution, unlike traditional fullerene-based superatomic crystals. The ion pairs can be further assembled into organometallic polymers using Janus-bis-(NHCs) to cross-link the oxidized M₄S₄ units. We show that the superatomic polymers are more conductive than both the precursor superatomic crystals and the polymers containing only neutral M₄S₄ clusters. Similar conductivity values can be obtained when neutral M₄S₄-NHC polymers are doped with solutions of C₆₀ fullerene. These findings demonstrate that next generation superatomic materials can be prepared via the combination of charge transfer and polymerization with appropriate cross-linking agents.