The bell-shaped energy gap dependence of the charge recombination reaction of geminate radical ion pairs produced by fluorescence quenching reaction in acetonitrile solution

Mataga, Noboru; Asahi, Tsuyoshi; Kanda, Yu; Okada, Tadashi; Kakitani, Toshiaki

doi:10.1016/0301-0104(88)87122-2

Cited by 208 publications

(191 citation statements)

References 31 publications

Supporting

Mentioning

179

Contrasting

Order By: Relevance

“…Indeed, if the quenching is sufficiently fast, such profiles exhibit a decay that can be well reproduced with an exponential function decaying to a constant value different from zero. 38,44,55 This decay, which supports the use of the exponential model, corresponds to the disappearance of the ion pair population by separation and CR, and the remaining plateau is due to the absorption of the long-lived free ion population. As shown in Figure 2A, such decay is not observed with Pe/DCB in ACN.…”

Section: Discussionsupporting

confidence: 54%

“…37 From this expression, CR of Pe •+ /DCB •-(∆G CR ) -2.62 eV) is substantially more exergonic than that of Pe •+ /DCE •-(∆G CR ) -2.34 eV). As CR of such ion pairs is well-known to exhibit the inverted behavior predicted by Marcus ET theory, 38,[41][42][43] it can be expected to be substantially slower with Pe •+ /DCB •-than with Pe •+ /DCE •-, as observed. Other parameters, such as the electronic coupling constant and the reorganization energy could also contribute to this difference.…”

Section: Resultsmentioning

confidence: 93%

See 1 more Smart Citation

Ultrafast Excited State Dynamics of the Perylene Radical Cation Generated upon Bimolecular Photoinduced Electron Transfer Reaction

2006

View full text Add to dashboard Cite

The ultrafast ground state recovery (GSR) dynamics of the radical cation of perylene, Pe•+, generated upon bimolecular photoinduced electron transfer in acetonitrile, has been investigated using pump−pump−probe spectroscopy. With 1,4-dicyanobenzene as electron acceptor, the free ion yield is substantial and the GSR dynamics of Pe•+ was found to depend on the time delay between the first and second pump pulses, Δt12, i.e., on the "age" of the ion. At short Δt12, the GSR dynamics is biphasic, and at Δt12 larger than about500 ps, it becomes exponential with a time constant around 3 ps. With trans-1,2-dicyanoethylene as acceptor, the free ion yield is essentially zero and the GSR dynamics of Pe•+ remains biphasic independently of Δt12. The change of dynamics observed with 1,4-dicyanobenzene is ascribed to the transition from paired to free solvated ion, because in the pair, the excited ion has an additional decay channel to the ground state, i.e., charge recombination followed by charge separation. The rate constants deduced from the analysis of these GSR dynamics are all fully consistent with this hypothesis

show abstract

Section: Discussionsupporting

confidence: 54%

Section: Resultsmentioning

confidence: 93%

Ultrafast Excited State Dynamics of the Perylene Radical Cation Generated upon Bimolecular Photoinduced Electron Transfer Reaction

2006

View full text Add to dashboard Cite

show abstract

“…This results in a large span of CR time constants going from a few hundreds of femtoseconds to values similar to or greater than the time constant for dissociation into free ions, which is on the order of 1 ns in ACN. [55][56][57][58] …”

Section: Chartmentioning

confidence: 99%

Simultaneous Generation of Different Types of Ion Pairs upon Charge-Transfer Excitation of a Donor−Acceptor Complex Revealed by Ultrafast Transient Absorption Spectroscopy

Mohammed

Vauthey

2008

J. Phys. Chem. A

View full text Add to dashboard Cite

The excited-state dynamics of the methylperylene/tetracyanoethylene (MPe/TCNE) donor-acceptor complex has been investigated in various solvents using femtosecond transient absorption spectroscopy. The transient spectra reveal the formation of two types of ion pairs: The first (IP1), constituting the major fraction of the total ion-pair population, is characterized by a broad and red-shifted absorption spectrum compared to that of the free MPe cation and by a subpicosecond lifetime, whereas the second (IP2) has a spectrum closer to that of MPe cation and a lifetime of a few picoseconds. A substantial polarization anisotropy was observed with IP1 but not with IP2, indicating a relatively well-defined structure for the former. The reaction scheme that best accounts for the observed dynamics and its solvent dependence involves the simultaneous excitation of complexes that differ by their electronic coupling. The more coupled complexes have a high absorption coefficient and thus yield IP1, which undergoes ultrafast charge recombination, whereas the less coupled complexes have a lower probability to be excited and lead to the longer-lived IP2.

show abstract

“…3,4 The stabilization of the charge-separated state by hydrogen bonding causes the modulation of the ÁG value for the CS and charge recombination reactions.…”

mentioning

confidence: 99%

“…3, 4 The stabilization of the charge-separated state by hydrogen bonding causes the modulation of the ÁG value for the CS and charge recombination reactions. [5][6][7][8][9][10][11] Recent time-resolved electron paramagnetic resonance (EPR) studies on solvent-separated radical ion pairs generated by photoinduced CS reactions suggest that values are also increased by solute-solvent hydrogen-bonding interactions in polar solvents.…”

mentioning

confidence: 99%

Ethanol Concentration Dependence of Photoinduced Charge Separation Reaction between Zinc Tetraphenylporphyrin and Duroquinone Studied by Laser Flash Photolysis

Yago

Gohdo²,

Wakasa³

2009

Chemistry Letters

View full text Add to dashboard Cite

Ethanol concentration dependence of photoinduced charge separation between zinc tetraphenylporphyrin (ZnTPP) and duroquinone (DQ) in benzonitrile was studied by nanosecond laser flash photolysis. Acceleration of the photoinduced charge separation reaction rate by hydrogen bonding between DQ anion radical and ethanol was observed. A simple analysis in the framework of the Marcus theory indicated that the observed electron-transfer reaction rate was affected not only by the decrease of the reaction free energy but also an increase of the reorganization energy in the presence of hydrogen bonding.Electron transfer (ET) is one of the most fundamental chemical reactions and has been studied extensively over the last six decades. Particular attention has been focused on biological ET systems where the reactions proceed with high efficiency.1 Hydrogen-bonding interactions are ubiquitous to biological ET systems and have been believed to contribute to efficient ET reactions by stabilizing the charge-separated states. Actually, Fukuzumi et al. have reported the acceleration of charge separation (CS) reactions in the presence of hydrogen-bonding interactions.2 According to the Marcus theory, the activation barrier for the ET reactions depends on reaction free energy (ÁG) and reorganization energy (). 3,4 The stabilization of the charge-separated state by hydrogen bonding causes the modulation of the ÁG value for the CS and charge recombination reactions.5-11 Recent time-resolved electron paramagnetic resonance (EPR) studies on solvent-separated radical ion pairs generated by photoinduced CS reactions suggest that values are also increased by solute-solvent hydrogen-bonding interactions in polar solvents.12 The results were interpreted with a change of chemical equilibrium for the hydrogen-bonding complex during the ET reactions; 13 however, the ET reaction rates have not been evaluated directly. It is, therefore, desirable to evaluate ET reaction rates directly in the presence of hydrogen bonding to clarify their role.In this contribution, we study ethanol concentration dependence of photoinduced CS between zinc tetraphenylporphyrin (ZnTPP) and duroquinone (DQ) in benzonitrile (PhCN) to clarify how the ET reaction rates are affected by the modulation of ÁG and in the presence of hydrogen bonding. For this purpose, nanosecond laser flash photolysis experiments were carried out with an apparatus that was essentially the same as an apparatus described elsewhere.14 The second harmonic (532 nm) of a Nd:YAG laser was used for the selective excitation of ZnTPP (1 Â 10 À4 M) in the sample solutions. The concentrations of DQ were 0.1-2 mM. To investigate the effect of hydrogen bonding on the CS reaction rates, ethanol (EtOH), which has been known to form hydrogen-bonding complexes with the DQ anion (DQ À ), was added to the sample solution. Since EtOH has a similar viscosity ( ¼ 1:08 cP) 15 and dielectric constant (" ¼ 24:6)15 as PhCN ( ¼ 1:24 cP, " ¼ 25:2), 15 the diffusion coefficients of solutes and macroscopic dielectric proper...

show abstract

The bell-shaped energy gap dependence of the charge recombination reaction of geminate radical ion pairs produced by fluorescence quenching reaction in acetonitrile solution

Cited by 208 publications

References 31 publications

Ultrafast Excited State Dynamics of the Perylene Radical Cation Generated upon Bimolecular Photoinduced Electron Transfer Reaction

Ultrafast Excited State Dynamics of the Perylene Radical Cation Generated upon Bimolecular Photoinduced Electron Transfer Reaction

Simultaneous Generation of Different Types of Ion Pairs upon Charge-Transfer Excitation of a Donor−Acceptor Complex Revealed by Ultrafast Transient Absorption Spectroscopy

Ethanol Concentration Dependence of Photoinduced Charge Separation Reaction between Zinc Tetraphenylporphyrin and Duroquinone Studied by Laser Flash Photolysis

Contact Info

Product

Resources

About