Manganese(I) carbonyls have been studied as photo-initiated carbon monoxide releasing molecules (photoCORMs) by the Ford Group1 and others.2 An alternative method of release was recently evaluated by He et al3 in which hydrogen peroxide, present in tumor cells, facilitates CO-release from manganese decacarbonyl (Mn2(CO)10) and exhibits cytotoxic effects. They attributed the observed cytotoxicity of Mn2(CO)10 to hydroxyl radical (HO.) production through Fenton-like chemistry.3 Alternatively, Poole et al found that HO. was not generated from MnBr(CO)3-Tris(2-pyridylmethyl)amine reaction with H2O2 without UV light irradiation.4 Understanding this reaction mechanism is vital to enable the potential therapeutic utilization of such compounds. Given that the mechanism by which H2O2 reacts with metal carbonyls is unknown, we have undertaken a quantitative kinetics and mechanistic study of this reaction with the model complex fac-Mn(CO)3(Br)(bpCO2H), (bpCO2H = 2,2’-bipyridine-4,4’-dicarboxylic acid). At physiological pH in phosphate buffered solution, the observed gaseous products were two equivalents CO and one equivalent CO2. At high concentrations a solid manganese product was isolated and contained a 1.5 to 1 Mn to PO4 ratio. Generation of HO. was evaluated using Coumarin-3-carboxyilic acid hydroxylation and fluorescence spectroscopy. Ongoing studies to observe and characterize reaction intermediates will be described.

Understanding the mechanism of hydrogen peroxide induced carbon monoxide release from a manganese carbonyl

2019 Fall National Meeting

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