Kinetics and thermodynamics of nitric oxide binding to transition metal complexes. Relationship to dioxygen binding

TitleKinetics and thermodynamics of nitric oxide binding to transition metal complexes. Relationship to dioxygen binding
Publication TypeJournal Article
Year of Publication2013
AuthorsBakac A, Pestovsky O, Durfey BL, Kristian KE
Journal TitleChemical Science
Volume4
Pages2185-2192
Date Published05/01
Type of ArticleArticle
ISBN Number2041-6520
Accession NumberWOS:000316966500033
Keywordsaqueous-solutions, binding, COORDINATION CHEMISTRY, electron-transfer reactions, macrocyclic ligands, molecular-oxygen, nitrous-acid, oxidation-reduction reactions, reversible, superoxochromium(iii) ion, superoxorhodium(iii) complex
Abstract

The kinetics and activation parameters for NO dissociation from L(H2O)Co(NO)(2+) (L = L-1 = cyclam and L-2 = meso-Me-6-cyclam), L-2(H2O)Rh(NO)(2+), and Cr(H2O)(5)NO2+ were determined in aqueous solution in the presence of IrCl62, IrBr62, or O-2 as scavengers for NO and/or metal(II) complexes. The rate constants k(-NO) at 25 degrees C are (5.7 +/- 0.1) x 10(-3) s(-1) for L-2(H2O)Co(NO)(2+), (1.0 +/- 0.1) x 10(-4) for L-1(H2O)Co(NO)(2+), (5.9 +/- 2.0) x 10(-8) for Cr(H2O)(5)NO2+ and (3.5 +/- 1.8) x 10(-9) s(-1) for L-2(H2O)Rh(NO)(2+). The kinetics of the reverse reaction were determined by laser flash photolysis at 25 degrees C, k(NO) = (1.7 +/- 0.2) x 10(7) M-1 s(-1) for (LCo)-Co-2(H2O)(2)(2+) and (1.8 +/- 0.1) x 10(8) M-1 s(-1) for L-2(H2O)Rh2+. The rate constants k(NO) and k(-NO) obtained here and those available in the literature were used to calculate the equilibrium binding constants K-NO for a series of nitrosyl metal complexes. A good correlation was found between log K-NO and log K-O2, the latter corresponding to O-2 binding. The correlation includes complexes of four different transition metals as well as hydrogen atom, and covers a range of about 3 V in reduction potentials. The implications of these results are discussed.

URL<Go to ISI>://WOS:000316966500033
DOI10.1039/c3sc50157d