The extraordinary versatility of the bipyridyl ruthenium class of redox-active complexes for device applications is based on a range of chemical properties that are largely ligand based within a robust and apparently unique molecular platform. Alternate chemical designs have been much less successful in terms of numbers of accessible redox levels or stability associated with them. The facilitation of redox activity in first-row transition metal complexes by the delocalization effects of ligands is a well-accepted axiom of coordination chemistry. In this regard nitrosyl (NO) and dithiolene ligands have served as paradigms for over five decades. A second strategy for promoting or engendering accessibility to redox processes in first row transition metals is to assemble two metals in close proximity such that the burden of charge build up as an election is added or removed from the unit is shared by both metals. Such a design is found within the active sites of several redox metalloproteins and enzyme active sites. In a search for other platforms that demonstrate stability in multiple redox levels, we have discovered a combination of sulfur-bridged Fe-Ni bimetallics that incorporate redox active ligands on each metal, NO on iron and dithiolene on nickel. Good reversibility in the two redox events of the neutral precursor prompted chemical explorations and isolation of the reduced and the oxidized Fe-Ni complexes. The electron most easily added to the neutral Fe-Ni bimetallic parent is on the Fe(NO), generating a rare example of {Fe(NO)}<sup>8</sup> and tight ion pairing at thiolate sulfurs, while the cationic species resulting from removal of an electron leads to dimerization between a pair of radical monoanion nickel dithiolene units. Further characterization includes Mossbauer data and solvent dependence on the monomer/dimer equilibrium that distinct spin states.

Redox level control of spin states by NO and dithiolenes in iron-nickel complexes

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.