Manganese Metal Carbonyl Complexes as CO-Releasing Molecules
O.H. Rogers1, B.E. Moulton2, A.K. Duhme-Klair2, and I.J. Fairlamb2
1Department of Biological Sciences, California State University Los Angeles 2 Department of Chemistry, The University of York, United Kingdom
Background: Carbon monoxide, a naturally occurring and biologically relevant gas, has long been known to have important biological functions within organisms. These functions include vasodilatory properties within cardiac muscle cells, which serve to minimize ischemia, tissue damage, and organ rejection after cardiac surgery. With the prospect of administering CO gas to a patient being out of the question, researchers have focused on synthesizing molecules to deliver CO to targeted areas of a patient. In this study manganese metal carbonyl complexes were investigated as potential thermally stable CO releasing molecules capable of liberating CO in controlled amounts through photolysis.
Methods: Two previously synthesized manganese metal carbonyl complexes, phenylpyridine manganese tetracarbonyl (PP) and benzoquinoline manganese tetracarbonyl (BQ), were studied for thermal stability following exposure to seven solvents of varying polarity. After stability in each solvent had been established, the stability of each molecule was determined in each of the seven solvents in the presence of PPh3 (triphenylphosphine). Finally, the stability of each molecule was investigated following photolysis in either DMSO or toluene alone and photolysis in either DMSO or toluene in the presence of PPh3.
Results: Both metal carbonyl complexes remained stable after exposure to each of the seven solvents. Additionally, both BQ and PP exhibited thermal stability in these solvents in the presence of PPh3. However; after photolysis of each compound in either DMSO or toluene, those samples dissolved in DMSO exhibited the reduction of initial metal carbonyl bands, as well as the growth of new bands in locations not previously seen. Furthermore, following photolysis of each compound in either DMSO or toluene and the presence of PPh3 all initial metal carbonyl bands in both samples exhibited a marked reduction. Those samples exposed to DMSO and PPh3 additionally showed the growth of new bands, while those samples exposed to toluene and PPh3 exhibited the complete diminishment of all metal carbonyl bands.
Conclusion: The results of this study indicate that both phenylpyridine manganese tetracarbonyl (PP) and benzoquinoline manganese tetracarbonyl (BQ) are thermally stable CO releasing molecules. These molecules have the capability of releasing targeted and controlled amounts of CO through photolysis and are thus excellent candidates for further studies of controlled and directed CO release.
Acknowledgements: Orquidea Rogers was supported by LA Basin Minority Health and Health Disparities International Research Training Program (MHIRT) 5T37MD001368-10 (National Center on Minority Health and Health Disparities). Funding for this project has also been provided by NIH MBRS-RISE award R25 GM61331 to O.H. Rogers.