The redox reactions of molecular substrates in biological systems are catalyzed by dehydrogenase and reductase enzymes. Many oxidative stress-related diseases, including diabetes, cardiovascular diseases, neurodegenerative disorders (such as Alzheimer's and Parkinson's), and cancer have been associated with deficiencies in these enzymes. Non-selective oxidation of lipids and carbohydrates under high oxidative stress may lead to the formation of toxic aldehydes, which can cause further disease progression. Our research goal is to develop a detoxification method utilizing small molecule intracellular metal catalysts (SIMCats) as reductase enzyme mimics to catalytically convert toxic aldehydes to non-toxic alcohols.<br/><br/>We have previously shown that pentamethylcyclopentadienyl (Cp*) iridium complexes are able to convert benzaldehyde to benzyl alcohol using formate as the hydride source under physiological conditions. To expand on this work, we have prepared multinuclear iridium transfer hydrogenation catalysts that shows higher activity per iridium in comparison to that of its mono iridium analogues, even at nanomolar iridium concentrations. Using a smaller amount of a metallotherapeutics will help reduce metal accumulation in the body and minimize drug toxicity.<br/><br/>The meta-linked version of the dinuclear iridium complex is a more effective catalyst as compared to the mononuclear and para-linked dinuclear counterparts in the hydrogenation of aldehyde. This could be attributed to the cooperative effect of the multiple iridium centers along with the overall electronic property of the complex. These findings further emphasize the importance of multimetal centers in enhancing catalytic activity. The new transfer hydrogenation catalysts may be utilized for the remediation of toxic aldehydes that are formed as a result of oxidative stress or exposure to environmental pollutants.

Bioinspired transfer hydrogenation using diiridium catalysts at nano molar concentrations

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