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Quantification of Carbon Monoxide from a Photochemical Carbon Monoxide Releasing Molecule (PhotoCORM) using a Binuclear Rhodium(II) Compound Kim Trevino, Meghan McCurry & Carmen F. Works Department of Chemistry, Sonoma State University Detection of CO in vitro: • Myoglobin assay is standard but is sensitive to oxidation. • Binuclear Rh-compounds present a colormetric solution. Background: • Fe-Fe hydrogenase enzymes catalyze the reversible oxidation of molecule hydrogen. The active site of Fe-Fe hydrogenase enzymes are organometallic. 1.2 1.0 0.8 Abs • 0.6 [Fe 4S4] S OC NC X S S 0.4 CO 0.2 Fe Fe C O CN OH 2 Enzyme Active Site • • • • • Model compounds of Fe-Fe Hydrogenase have been shown to release CO upon irradiation. CO is best known as a silent killer, but it is also recognized as a small molecule signaling agent produced through heme catabolism which is catalyzed by heme oxygenase. There are two isozymes of heme oxygenase (HO) known as HO-1 and HO-2 and both generate CO in vivo. Photochemical carbon monoxide releasing molecules (PhotoCORMs) have the potential for achieving a safe and controlled delivery of CO to specific targets. To help quantitate the photochemistry of CO release we’ve employed a binuclear rhodium(II) compound, [Rh2 {(C6H4)P(C6H5)2}2 (02CCH3)2] • (CH3CO2H)2 . Scheme 1. The oxidation of heme by heme oxygense producing CO in vivo. Chem. Commun., 2007, 4197-4208 0.0 400 Figure 2. Color changes observed with the addition of CO to the rhodium compound. Synthetic approach to develop PhotoCORMs using Fe-Fe Hydrogenase model compounds, which allow for a versatile synthetic platform: hn S S OC -CO Fe OC OC OC Fe OC L 700 800 Figure 3. Changes in the optical spectra of both (µ-pdt)Fe2(CO)6 and [Rh2 irradiation of 365 nm light. O Fe CO Table 1. Quantum Yield Data for PDT and Rhodium in methylene chloride, upon irradiation of 365 nm light. CO CO Fe 600 {(C6H4)P(C6H5)2}2 (02CCH3)2] • (CH3CO2H)2 in methylene chloride, upon Fe2(m-pdt)(CO)6 S S 500 nm CO L L = CO, CN- or PR3 PDT Rh 0.17 0.13 0.16 0.11 0.13 0.09 0.15 0.10 Wavelength 365 nm Quantum Yield 0.15 ± 0.08 1.0 0.8 0.6 Absorbance Cys 0.4 0.2 0.0 250 Figure 1. Spectral changes of Fe2(m-pdt)(CO)6 in THF when irradiated with 365 nm light. Monitored by IR. 300 350 Wavelength (nm) 400 450 Figure 1. Top: Spectral changes of Fe2(mpdt)(CO)6 in THF when irradiated with 365 nm light. Bottom: Spectral changes for FeMET in acetonitrile when irradiated with 334 nm light 500 Acknowledgments: We would like to thank the Chemistry Division of the National Science Foundation (NSFCHE-1057808) , LSAMP NSF grant HRD-1302873, McNair Scholars Program, Presidential Scholar Jaimey Homen, and CSUPERB for support.