Electrically conductive [Fe4S4]-based organometallic polymers

Abstract

Tailoring the molecular components of hybrid organic–inorganic materials enables precise control over their electronic properties. Designing electrically conductive coordination materials, e.g. metal–organic frameworks (MOFs), has relied on single-metal nodes because the metal–oxo clusters present in the vast majority of MOFs are not suitable for electrical conduction due to their localized electron orbitals. Therefore, the development of metal-cluster nodes with delocalized bonding would greatly expand the structural and electrochemical tunability of conductive materials. Whereas the cuboidal [Fe₄S₄] cluster is a ubiquitous cofactor for electron transport in biological systems, few electrically conductive artificial materials employ the [Fe₄S₄] cluster as a building unit due to the lack of suitable bridging linkers. In this work, we bridge the [Fe₄S₄] clusters with ditopic N-heterocyclic carbene (NHC) linkers through charge-delocalized Fe–C bonds that enhance electronic communication between the clusters. [Fe₄S₄Cl₂(ditopic NHC)] exhibits a high electrical conductivity of 1 mS cm⁻¹ at 25 °C, surpassing the conductivity of related but less covalent materials. These results highlight that synthetic control over individual bonds is critical to the design of long-range behavior in semiconductors.