title: Dinuclear PhotoCORMs: Dioxygen-Assisted Carbon Monoxide Uncaging from Long-Wavelength-Absorbing Metal-Metal-Bonded Carbonyl Complexes.
abstract: We describe a new strategy for triggering the photochemical release of caged carbon monoxide (CO) in aerobic media using long-wavelength visible and near-infrared (NIR) light. The dinuclear rhenium-manganese carbonyl complexes (CO)5ReMn(CO)3(L), where L = phenanthroline (1), bipyridine (2), biquinoline (3), or phenanthrolinecarboxaldehyde (4), each show a strong metal-metal-bond-to-ligand (σMM→ πL*) charge-transfer absorption band at longer wavelengths. Photolysis with deep-red (1 and 2) or NIR (3 and 4) light leads to homolytic cleavage of the Re-Mn bonds to give mononuclear metal radicals. In the absence of trapping agents, these radicals primarily recombine to reform dinuclear complexes. In oxygenated media, however, the radicals react with dioxygen to form species much more labile toward CO release via secondary thermal and/or photochemical reactions. Conjugation of 4, with an amine-terminated poly(ethylene glycol) oligomer, gives a water-soluble derivative with similar photochemistry. In this context, we discuss the potential applications of these dinuclear complexes as visible/NIR-light-photoactivated CO-releasing moieties (photoCORMs).
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Barbara , Santa Barbara, California 93106-9510, United States.
authors.forename: Zhi
authors.initials: Z
authors.lastname: Li
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Barbara , Santa Barbara, California 93106-9510, United States.
authors.forename: Agustin E
authors.initials: AE
authors.lastname: Pierri
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Barbara , Santa Barbara, California 93106-9510, United States.
authors.forename: Po-Ju
authors.initials: PJ
authors.lastname: Huang
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Barbara , Santa Barbara, California 93106-9510, United States.
authors.forename: Guang
authors.initials: G
authors.lastname: Wu
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Barbara , Santa Barbara, California 93106-9510, United States.|Department of Chemistry and Environmental Sciences, Lake Superior State University , Sault Sainte Marie, Michigan 49783, United States.
authors.forename: Alexei V
authors.initials: AV
authors.lastname: Iretskii
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Barbara , Santa Barbara, California 93106-9510, United States.
authors.forename: Peter C
authors.identifier: http://orcid.org/0000-0002-5509-9912
authors.initials: PC
authors.lastname: Ford