Lifetimes, spectra, and quenching of the excited states of polypyridine complexes of iron(II), ruthenium(II), and osmium(II)

Creutz, Carol; Chou, Mei H.; Netzel, Thomas L.; Okumura, Mitchio; Sutin, Norman

doi:10.1021/ja00524a014

Cited by 465 publications

(364 citation statements)

References 12 publications

Supporting

Mentioning

325

Contrasting

Order By: Relevance

“…This pattern can be assigned to an osmium-to-bpy charge transfer, 3 MLCT, excited state. 83 The 3 MLCT lifetime of Os2c is 29 ns in air-equilibrated THF, once again in excellent agreement with the lifetime obtained from the emission measurements.…”

Section: Resultssupporting

confidence: 82%

Synthesis, Photophysical, Photochemical, and Redox Properties of Nitrospiropyrans Substituted with Ru or Os Tris(bipyridine) Complexes

et al. 2006

View full text Add to dashboard Cite

Photochromic nitrospiropyrans substituted with 2,2′-bipyridine (bpy), [Ru(bpy) , resulting in energy transfer from the excited ruthenium center to the spiropyran but inversely in the osmium case. The open merocyanine form reduces and oxidizes electrochemically more easily than the closed nitrospiropyran. Like photoexcitation, electrochemical activation also causes opening of the spiropyran ring by first reducing the closed form and subsequently reoxidizing the corresponding radical anion in two wellresolved anodic steps. Interestingly, the substitution of the spiropyran with a Ru or Os metal center does not affect the efficiency of this electrochemically induced ring-opening process, different from the photochemical path.

show abstract

Section: Resultssupporting

confidence: 82%

Synthesis, Photophysical, Photochemical, and Redox Properties of Nitrospiropyrans Substituted with Ru or Os Tris(bipyridine) Complexes

et al. 2006

View full text Add to dashboard Cite

show abstract

“…S3). TA traces of Ru II K97C -Fe III P450 following excitation in the absence of exogenous quencher (pH 8, λ ex ¼ 480 nm, 10 ns pulse) reveals bleaching (ΔAbs < 0) at wavelengths corresponding to Ru II absorption (390-440 nm), consistent with the well-characterized behavior of metal-to-ligand charge-transfer (MLCT) excited Ru-diimine complexes (13). The transient signal returns to baseline at the same rate as luminescence decays and we find no evidence for transient species associated with changes in heme Soret absorption.…”

supporting

confidence: 64%

Photooxidation of cytochrome P450-BM3

Ener

Lee

Winkler

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

109

View full text Add to dashboard Cite

High-valent iron-oxo species are thought to be intermediates in the catalytic cycles of oxygenases and peroxidases. An attractive route to these iron-oxo intermediates involves laser flash-quench oxidation of ferric hemes, as demonstrated by our work on the ferryl (compound II) and ferryl porphyrin radical cation (compound I) intermediates of horseradish peroxidase. Extension of this work to include cytochrome P450-BM3 (CYP102A1) has required covalent attachment of a Ru II photosensitizer to a nonnative cysteine near the heme (Ru II K97C -Fe III P450 ), in order to promote electron transfer from the Fe III porphyrin to photogenerated Ru III . The Ru II K97C -Fe III P450 conjugate was structurally characterized by X-ray crystallography (2.4 Å resolution; Ru-Fe distance, 24 Å). Flash-quench oxidation of the ferric-aquo heme produces an Fe IV -hydroxide species (compound II) within 2 ms. Difference spectra for three singly oxidized P450-BM3 intermediates were obtained from kinetics modeling of the transient absorption data in combination with generalized singular value decomposition analysis and multiexponential fitting.ruthenium bipyridine | enzyme catalysis T he cytochromes P450 constitute a superfamily of thiolateligated heme enzymes so named because the Soret absorption band in their CO-bound derivatives peaks near 450 nm. These monooxygenases catalyze a dazzling array of regio-and stereospecific oxidation reactions, including the hydroxylation of aliphatic and aromatic hydrocarbons and the epoxidation of alkenes (1, 2). P450s take two reducing equivalents from NAD(P)H and deliver one atom from dioxygen to the organic substrate; the other oxygen atom is released as water. The consensus mechanism for P450 catalysis (Fig. 1) implicates a ferryl porphyrin radical cation [compound I (CI): Fig. 1, intermediate 6] as the active oxygenating agent (3), but this elusive species has not been observed in P450 under single-turnover or steady-state catalytic conditions. In the postulated mechanism, CI is proposed to abstract a hydrogen atom from the substrate to form transient Fe IV -hydroxide complex (compound II, CII), followed by radical recombination to produce oxygenated product (4, 5). Mechanistic studies of P450 catalysis in cryogenic matrices have suggested that the barrier to formation of CI (5 → 6) is higher than that for its reaction with substrate (6 → 7 → 1) (6). Consequently, recent efforts have focused on alternate routes to P450 CI that bypass the hydroperoxide intermediate (5). One approach employs generation of CII using peroxynitrite, followed by laser flash photolysis to yield CI (7). This technique has been used in studies of the spectra and reactivity of the putative CI species, but the interpretation of the results remains open to question.In earlier work, we employed ½RuðbpyÞ 3 2þ (bpy ¼ 2;2 0 -bipyridine) in a bimolecular flash-quench photochemical oxidation protocol to generate CII and CI in horseradish peroxidase (HRP) and the heme octapeptide from cyctochrome c (MP8) (8, 9). This approach was uns...

show abstract

“…380 nm that has been used as evidence for the presence of the radical anion of bpy. 49,50 The nature of the THEXI state can therefore be concluded to be either 3 (π → π*) or LCCT. MO pictures from triplet-state calculations (see Figure 13 for an example involving [Re(CO) 3 Cl(DPA)] + )…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Synthesis, Characterization, and Photophysics of Oxadiazole- and Diphenylaniline-Substituted Re(I) and Cu(I) Complexes

et al. 2013

View full text Add to dashboard Cite

Transition-metal complexes of the types [Re(CO)3Cl(NN)], [Re(CO)3py(NN)]+, and [Cu(PPh3)2(NN)]+, where NN = 4,4′-bis(5-phenyl-1,3,4-oxadiazol-2-yl)-2,2′-bipyridine (OX) and 4, 4′-bis(N,N-diphenyl-4-[ethen-1-yl]-aniline)-2,2′-bipyridine (DPA), have been synthesized and characterized. Crystal structures for [Re(CO)3Cl(DPA)] and [Cu(PPh3)2(OX)]BF4 are presented. The crystal structure of the rhenium complex shows a trans arrangement of the ethylene groups, in agreement with density functional theory calculations. The structure of the copper complex displays the planar aromatic nature of the bpy-oxadiazole ligand. Density functional theory modeling of the complexes was supported by comparison of calculated and experimental normalized Raman spectra; the mean absolute deviations of the complexes were <10 >cm-1. The Franck-Condon state was investigated using UV-vis and resonance Raman spectroscopic as well as density functional theory computational techniques. It was shown that the lowest energy absorption peaks are metal to ligand charge transfer and ligand-centered charge transfer for the oxadiazole-and diphenylaniline-substituted bipyridine ligands, respectively. The lowest energy excited states were characterized using transient emission and absorption spectroscopic techniques in conjunction with density functional theory calculations. These showed that the DPA complexes had ligand-centered nonemissive "dark" states with lifetimes ranging from 300 to 2000 ns. The crystal structure of the rhenium complex shows a trans arrangement of the ethylene groups, in agreement with density functional theory calculations. The structure of the copper complex displays the planar aromatic nature of the bpy−oxadiazole ligand. Density functional theory modeling of the complexes was supported by comparison of calculated and experimental normalized Raman spectra; the mean absolute deviations of the complexes were <10 cm −1 . The Franck−Condon state was investigated using UV−vis and resonance Raman spectroscopic as well as density functional theory computational techniques. It was shown that the lowest energy absorption peaks are metal to ligand charge transfer and ligand-centered charge transfer for the oxadiazole-and diphenylaniline-substituted bipyridine ligands, respectively. The lowest energy excited states were characterized using transient emission and absorption spectroscopic techniques in conjunction with density functional theory calculations. These showed that the DPA complexes had ligand-centered nonemissive "dark" states with lifetimes ranging from 300 to 2000 ns.

show abstract

Lifetimes, spectra, and quenching of the excited states of polypyridine complexes of iron(II), ruthenium(II), and osmium(II)

Cited by 465 publications

References 12 publications

Synthesis, Photophysical, Photochemical, and Redox Properties of Nitrospiropyrans Substituted with Ru or Os Tris(bipyridine) Complexes

Synthesis, Photophysical, Photochemical, and Redox Properties of Nitrospiropyrans Substituted with Ru or Os Tris(bipyridine) Complexes

Photooxidation of cytochrome P450-BM3

Synthesis, Characterization, and Photophysics of Oxadiazole- and Diphenylaniline-Substituted Re(I) and Cu(I) Complexes

Contact Info

Product

Resources

About