A Ruthenium Pterin Complex Showing Proton‐Coupled Electron Transfer: Synthesis and Characterization

Kojima, Takahiko; Sakamoto, T.; Matsuda, Yoshihisa; Ohkubo, Kei; Fukuzumi, Shunichi

doi:10.1002/anie.200352111

Cited by 28 publications

(9 citation statements)

References 36 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Redox potentials of 1 , 2 , 3 , and 4 had been measured previously 21 –23. Reversible one-electron redox couples assigned to Ru(II)/Ru(III) were observed at 0.55 V (vs Fc/Fc + , Δ E = 60 mV) for 1 and 0.52 V (Δ E = 64 mV) for 2 .…”

Section: Resultsmentioning

confidence: 68%

“…The reversible two-step protonation/deprotonation behavior was observed in absorption spectra of 3 and 4 in aqueous buffer solutions and in MeCN by adding HClO 4 or base as reported previously. 22,23 The spectroscopic titrations were carried out to determine the pK a of 3 and 4 in MeCN by using Hdcba (pK a ) 17.6) for the first protonation steps. The absorption spectrum of 3 changed into that of 1 by addition of an excess amount of Hdcba as shown in Figure 1a.…”

Section: Resultsmentioning

confidence: 99%

“…Redox potentials of 1, 2, 3, and 4 had been measured previously. [21][22][23] Reversible one-electron redox couples assigned to Ru(II)/Ru(III) were observed at 0.55 V (vs Fc/Fc + , ∆E ) 60 mV) for 1 and 0.52 V (∆E ) 64 mV) for 2. Those values are 0.28 and 0.26 V higher than those observed for 3 (0.27 V) and 4 (0.26 V), respectively; however, they are only 0.2 V lower than those of the corresponding doubly protonated species (see Scheme 2).…”

Section: Resultsmentioning

confidence: 99%

“…Phenols were further purified by the standard methods 24. 2,4,6-Tri- tert -buthylphenol- d ,25 [Ru(Hdmp)(TPA)](ClO 4 ) 2 ( 1 ),21 [Ru(Hdmdmp)(TPA)](ClO 4 ) 2 ( 2 ),21 [Ru(dmp − )(TPA)]ClO 4 ( 3 ),22 and [Ru(dmdmp − )(TPA)]ClO 4 ( 4 ),22,23 were prepared according to literature methods. NMR measurements were performed on JEOL AL-300 and Bruker AV-300 spectrometers.…”

Section: Methodsmentioning

confidence: 99%

See 3 more Smart Citations

Proton-Coupled Electron Transfer of Ruthenium(III)−Pterin Complexes: A Mechanistic Insight

et al. 2009

Self Cite

View full text Add to dashboard Cite

Ruthenium(II) complexes having pterins of redox-active heteroaromatic coenzymes as ligands were demonstrated to perform multistep proton transfer (PT), electron transfer (ET), and protoncoupled electron transfer (PCET) processes. Thermodynamic parameters including pK a , bond dissociation energy (BDE) of multistep PCET processes in acetonitrile (MeCN) were determined for ruthenium-pterin complexes, [Ru II (Hdmp) (Hdmp = 6, Hdmdmp = N,7-dimethylpterin, TPA = tris(2-pyridylmethyl)amine), all of which had been isolated and characterized before. The BDE difference between 1 and one-electron oxidized species, [Ru III (dmp − )(TPA)] 2+ , was determined to be 89 kcal mol −1 , which was large enough to achieve hydrogen atom transfer (HAT) from phenol derivatives. In the HAT reactions from phenol derivatives to [Ru III (dmp − )(TPA)] 2+ , the second-order rate constants (k) were determined to exhibit a linear relationship with BDE values of phenol derivatives with a slope (−0.4), suggesting that this HAT is simultaneous proton and electron transfer. As for HAT reaction from 2,4,6-tri-tert-buthylphenol (TBP; BDE = 79.15 kcal mol −1 ) to [Ru III (dmp − ) (TPA)] 2+ , the activation parameters were determined to be ΔH ‡ = 1.6 ± 0.2 kcal mol −1 and ΔS ‡ = −36 ± 2 cal K −1 mol −1 . This small activation enthalpy suggests a hydrogen-bonded adduct formation prior to HAT. Actually, in the reaction of 4-nitrophenol with [Ru III (dmp − )(TPA)] 2+ , the second-order rate constants exhibited saturation behavior at higher concentrations of the substrate and low-temperature ESI-MS allowed us to detect the hydrogen-bonding adduct. This also lends credence to an associative mechanism of the HAT involving intermolecular hydrogen bonding between the deprotonated dmp ligand and the phenolic O-H to facilitate the reaction. In particular, a two-point hydrogen bonding between the complex and the substrate involving the 2-amino group of the deprotonated pterin ligand effectively facilitates the HAT reaction from the substrate to the Ru(III)-pterin complex.kojima@chem.tsukuba.ac.jp (T. K.), mayer@chem.washington.edu (J. M. M.) and fukuzumi@chem.eng.osaka-u.ac.jp. † Osaka University ‡ Present address: Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tennou-dai, Tsukuba, Ibaraki 305-8571, Japan. § University of Washington Supporting Information Available: UV-vis spectra in the spectroscopic titrations to determine the pK a values, the ESR spectrum of 2,4,6-tri-tert-butyl phenoxyl radical obtained by the hydrogen atom transfer reaction from 2,4,6-tri-tert-butyl phenol to [Ru III (dmp − ) (TPA)] 2+ , the mass spectrum of the reaction product of 4-nitrophenol with [Ru III (dmp − )(TPA)] 2+ . This material is available free of charge via the Internet at

show abstract

Section: Resultsmentioning

confidence: 68%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 2 more Smart Citations

Proton-Coupled Electron Transfer of Ruthenium(III)−Pterin Complexes: A Mechanistic Insight

et al. 2009

Self Cite

View full text Add to dashboard Cite

show abstract

“…We recently reported that a ruthenium fragment based on the tetradentate ligand tris[(pyridin-2-yl)methyl]amine (TPA, Figure ) is an effective photocaging group for nitriles . Even though the Ru(TPA) motif had been investigated in photochemical molecular machines and switches, − oxidation − and hydrogenation catalysts, DNA metallointercalators, and for proton-coupled electron transfer properties, − its behavior as a photocaging group had only been investigated for release of nitric oxide . Gratifyingly, Ru(TPA) showed promising activity as a caging group for nitriles, including stability in buffer and high selectivity for enzyme inhibition under dark versus light conditions.…”

Section: Introductionmentioning

confidence: 99%

Effects of Methyl Substitution in Ruthenium Tris(2-pyridylmethyl)amine Photocaging Groups for Nitriles

et al. 2016

View full text Add to dashboard Cite

Four complexes of the general formula [Ru(L)(CH3CN)2](PF6)2, [L = TPA (5), MeTPA (6), Me2TPA (7), and Me3TPA (8)] [TPA = tris[(pyridin-2-yl)methyl]amine, where methyl groups were introduced consecutively onto the 6-position of py donors of TPA, were prepared and characterized by various spectroscopic techniques and mass spectrometry. While 5 and 8 were isolated as single stereoisomers, 6 and 7 were isolated as mixtures of stereoisomers in 2:1 and 1.5:1 ratios, respectively. Steric effects on ground state stability and thermal and photochemical reactivities were studied for all four complexes using 1H NMR and electronic absorption spectroscopies and computational studies. These studies confirmed that the addition of steric bulk accelerates photochemical and thermal nitrile release.

show abstract

Flavin Photocatalysts with Substrate Binding Sites

Schmaderer

Svoboda

König

2009

Activating Unreactive Substrates

View full text Add to dashboard Cite

A Ruthenium Pterin Complex Showing Proton‐Coupled Electron Transfer: Synthesis and Characterization

Cited by 28 publications

References 36 publications

Proton-Coupled Electron Transfer of Ruthenium(III)−Pterin Complexes: A Mechanistic Insight

Proton-Coupled Electron Transfer of Ruthenium(III)−Pterin Complexes: A Mechanistic Insight

Effects of Methyl Substitution in Ruthenium Tris(2-pyridylmethyl)amine Photocaging Groups for Nitriles

Flavin Photocatalysts with Substrate Binding Sites

Contact Info

Product

Resources

About