Protonation equilibria in excited-state tris(bipyrazine)ruthenium(II)

Crutchley, Robert J.; Kress, N.; Lever, A. B. P.

doi:10.1021/ja00343a016

Cited by 83 publications

(47 citation statements)

References 6 publications

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“…For [Ru(bpy) 2 (DPPZ)] 2+ protonation occurs on the phenazine ring, and the first protonation prevents a second protonation due to electronic repulsion. Analyzing the changes in luminescence intensity with pH allowed Turro’s group to extrapolate an apparent excited state pKa* of 2.1 for [Ru(bpy) 2 (dpqp)] 2+ , which is in the classical pKa range for related ruthenium complexes [108,109,110,111] (Table 1).…”

Section: Mononuclear Rutheniumii Complexesmentioning

confidence: 99%

RutheniumII Complexes bearing Fused Polycyclic Ligands: From Fundamental Aspects to Potential Applications

Troian‐Gautier

Moucheron

2014

Molecules

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Section: Mononuclear Rutheniumii Complexesmentioning

confidence: 99%

RutheniumII Complexes bearing Fused Polycyclic Ligands: From Fundamental Aspects to Potential Applications

Troian‐Gautier

Moucheron

2014

Molecules

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“…From the inflection point in an emission maximum wavelength versus pH plot (see Supporting Information) an apparent pK 1 * value of 2.4 AE 0.3 was extracted. However, since a true thermodynamic acidbase equilibrium is not necessarily established within the lifetime of the excited state (< 1 ms), the correct pK 1 * value for the imidazole protonation in the excited state is calculated using Equation (1) [30] based on the Fçrster thermodynamic cycle: [31] and references therein…”

Section: Photochemistrymentioning

confidence: 99%

Influence of the Protonic State of an Imidazole‐Containing Ligand on the Electrochemical and Photophysical Properties of a Ruthenium(II)–Polypyridine‐Type Complex

Quaranta

Lachaud

Herrero

et al. 2007

Chemistry A European J

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The synthesis and characterisation of [Ru(bpy)2(PhenImHPh)]2+ where PhenImHPh represents the 2-(3,5-di-tert-butylphenyl)imidazo[4,5-f][1,10]phenanthroline ligand are described. The compounds issued from the three different protonic states of the imidazole ring [Ru(bpy)2(PhenImPh)]+ (I), [Ru(bpy)2(PhenImHPh)]2+ (II) and [Ru(bpy)2(PhenImH2Ph)]3+ (III) were isolated and spectroscopically characterised. The X-ray structures of [Ru(bpy)2(PhenImPh)](PF6)H2O.6 MeOH, [Ru(bpy)2(PhenImHPh)](NO3)2H2O.3 MeOH and [Ru(bpy)2(PhenImH2Ph)](PF6)3 5 H2O are reported. Electrochemical data obtained on these complexes indicate almost no potential shift for the Ru(III/II) redox couple. Therefore a Coulombic effect between the imidazole ring and the metal centre can be ruled out. The monooxidised forms of I and II have been characterised by EPR spectroscopy and are reminiscent of the presence of a radical species. The emission properties of the parent compound [Ru(bpy)2(PhenImHPh)]2+ were studied as a function of pH and both the lifetimes and intensities decreased upon deprotonation. Photophysical properties, investigated in the absence and presence of an electron acceptor (methylviologen), were distinctly different for the three compounds. Transient absorption features indicate that unique excited states are involved. Theoretical data obtained from DFT calculations in water on the three protonic forms are presented and discussed in the light of the experimental results.

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“…On the other hand, the acid/base groups located on the ligand that accepts the electronic density upon MLCT excitation will become more basic. [20][21][22][23][24] Here, we report an investigation of electronic properties of a Ru-based complex, Ru-bpm, that contains a bipyrimidine ligand capable of accepting electrons and protons under the applied potential or visible light photoexcitation (Scheme 1). Electrochemical, spectroscopic and computational studies were utilized to investigate the ground and excited-state electron and proton transfer chemistry of Ru-bpm.…”

Section: Introductionmentioning

confidence: 99%

Proton-coupled Electron Transfer in a Ruthenium (II) Bipyrimidine Complex in its Ground and Excited Electronic States

Drummer

Weerasooriya

Gupta

et al. 2022

Preprint

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Proton-coupled electron transfer (PCET) was studied for the ground and excited electronic states of a [Ru(terpy)(bpm)(OH2)(PF6)] complex, Ru-bpm. Cyclic voltammetry measurements show that the Ru(II)-aqua moiety undergoes PCET to form Ru(IV)-oxo moiety in the anodic region, while the bpm ligand undergoes PCET to form bpmH2 in the anodic region. The photophysical behavior of Ru-bpm was studied using steady-state and femtosecond transient UV-vis absorption spectroscopy, coupled with density functional theory (DFT) calculations. The lowest-lying excited state of Ru-bpm is described as a (Ru bpm) metal-to-ligand charge transfer (MLCT) state, while the metal-centered (MC) excited state was found computationally to be close in energy to the lowest-energy bright MLCT state (MC state was 0.16 eV above the MLCT state). The excited state kinetics of Ru-bpm were found via transient absorption spectroscopy to be short-lived and were fit well to a biexponential function with lifetimes 1=4 ps and 2=65 ps in aqueous solution. Kinetic isotope effect of 1.75 was observed for both decay components, indicating that the solvent plays an important role in the excited-state dynamics of Ru-bpm. Based on the pH-dependent studies and the results from prior studies of similar Ru-complexes, we hypothesize that the 3MLCT state forms an excited-state hydrogen-bond adduct with the solvent molecules and that this process occurs with the 4 ps lifetime. The formation of such hydrogen-bond complex is consistent with the electronic density accumulation at the peripheral N atoms of the bpm moiety in the 3MLCT state. The hydrogen-bonded state 3MLCT’ decays to the ground state with a 65 ps lifetime. Such short lifetime is likely associated with the efficient vibrational energy transfer from 3MLCT state to the solvent.

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Protonation equilibria in excited-state tris(bipyrazine)ruthenium(II)

Cited by 83 publications

References 6 publications

RutheniumII Complexes bearing Fused Polycyclic Ligands: From Fundamental Aspects to Potential Applications

RutheniumII Complexes bearing Fused Polycyclic Ligands: From Fundamental Aspects to Potential Applications

Influence of the Protonic State of an Imidazole‐Containing Ligand on the Electrochemical and Photophysical Properties of a Ruthenium(II)–Polypyridine‐Type Complex

Proton-coupled Electron Transfer in a Ruthenium (II) Bipyrimidine Complex in its Ground and Excited Electronic States

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