Electronic isomerism in a heterometallic nickel-iron-sulfur cluster models substrate binding and cyanide inhibition of carbon monoxide dehydrogenase.

The nickel-iron carbon monoxide dehydrogenase (CODH) enzyme uses a heterometallic nickel-iron-sulfur ([NiFeS]) cluster to catalyze the reversible interconversion of carbon dioxide (CO) and carbon monoxide (CO). These reactions are essential for maintaining the global carbon cycle and offer a route towards sustainable greenhouse gas conversion but have not been successfully replicated in synthetic models, in part due to a poor understanding of the natural system. Though the general protein architecture of CODH is known, the electronic structure of the active site is not well-understood, and the mechanism of catalysis remains unresolved.

Enzyme Control Over Ferric Iron Magnetostructural Properties.

Fe complexes in aqueous solution can exist as discrete mononuclear species or multinuclear magnetically coupled species. Stimuli-driven change to Fe speciation represents a powerful mechanistic basis for magnetic resonance sensor technology, but ligand design strategies to exert precision control of aqueous Fe magnetostructural properties are entirely underexplored. In pursuit of this objective, we rationally designed a ligand to strongly favor a dinuclear μ-oxo-bridged and antiferromagnetically coupled complex, but which undergoes carboxylesterase mediated transformation to a mononuclear high-spin Fe chelate resulting in substantial T -relaxivity increase.

Reversible Electron Transfer and Substrate Binding Support [NiFeS] Ferredoxin as a Protein-Based Model for [NiFe] Carbon Monoxide Dehydrogenase.

The nickel-iron carbon monoxide dehydrogenase (CODH) enzyme catalyzes the reversible and selective interconversion of carbon dioxide (CO) to carbon monoxide (CO) with high rates and negligible overpotential. Despite decades of research, many questions remain about this complex metalloenzyme system. A simplified model enzyme could provide substantial insight into biological carbon cycling.

Rational Ligand Design Enables pH Control over Aqueous Iron Magnetostructural Dynamics and Relaxometric Properties.

Complexes of Fe engage in rich aqueous solution speciation chemistry in which discrete molecules can react with solvent water to form multinuclear μ-oxo and μ-hydroxide bridged species. Here we demonstrate how pH- and concentration-dependent equilibration between monomeric and μ-oxo-bridged dimeric Fe complexes can be controlled through judicious ligand design. We purposed this chemistry to develop a first-in-class Fe-based MR imaging probe, Fe-PyCy2AI, that undergoes relaxivity change via pH-mediated control of monomer vs dimer speciation.

The good, the neutral, and the positive: buffer identity impacts CO reduction activity by nickel(ii) cyclam.

Development of new synthetic catalysts for CO reduction has been a central focus of chemical research efforts towards mitigating rising global carbon dioxide levels. In parallel with generating new molecular systems, characterization and benchmarking of these compounds across well-defined catalytic conditions are essential. Nickel(ii) cyclam is known to be an active catalyst for CO reduction to CO.