Studies of carbon monoxide release from ruthenium(II) bipyridine carbonyl complexes upon UV-light exposure

Manja Kubeil, Robbin R Vernooij, Clemens Kubeil, Bayden R Wood, Bim Graham, Holger Stephan, Leone Spiccia

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Abstract

The UV-light-induced CO release characteristics of a series of ruthenium(II) carbonyl complexes of the form trans-Cl[RuLCl2(CO)2] (L = 4,4′-dimethyl-2,2′-bipyridine, 4′-methyl-2,2′-bipyridine-4-carboxylic acid, or 2,2′-bipyridine-4,4′-dicarboxylic acid) have been elucidated using a combination of UV-vis absorbance and Fourier transform infrared spectroscopies, multivariate curve resolution alternating least-squares analysis, and density functional theory calculations. In acetonitrile, photolysis appears to proceed via a serial three-step mechanism involving the sequential formation of [RuL(CO)(CH3CN)Cl2], [RuL(CH3CN)2Cl2], and [RuL(CH3CN)3Cl]+. Release of the first CO molecule occurs quickly (k1 ≫ 3 min-1), while release of the second CO molecule proceeds at a much more modest rate (k2 = 0.099-0.17 min-1) and is slowed by the presence of electron-withdrawing carboxyl substituents on the bipyridine ligand. In aqueous media (1% dimethyl sulfoxide in H2O), the two photodecarbonylation steps proceed much more slowly (k1 = 0.46-1.3 min-1 and k2 = 0.026-0.035 min-1, respectively) and the influence of the carboxyl groups is less pronounced. These results have implications for the design of new light-responsive CO-releasing molecules ("photoCORMs") intended for future medical use.

Original languageEnglish
Pages (from-to)5941-5952
Number of pages12
JournalInorganic Chemistry
Volume56
Issue number10
DOIs
Publication statusPublished - 15 May 2017

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