Pressure Tuning of Solvent Relaxation Time for the Excited Intramolecular Charge-Transfer Kinetics in 4-(<i>N</i>,<i>N</i>-Dimethylamino)triphenylphosphine in Alcohol

Kometani, Noritsugu; Kajimoto, Okitsugu; Hara, Kimihiko

doi:10.1021/jp9640787

Cited by 11 publications

(7 citation statements)

References 30 publications

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“…The exponent of the viscosity term is expected to be 1 on the basis of Kramers theory, 34 but in many cases it is found experimentally to be less than one. [35][36][37][38][39][40][41][42][43][44][45] Frequency-dependent friction near the top of the barrier is often invoked to explain the fractional exponent, which is thought to reflect the sharpness of the barrier, a sharper barrier leading to a smaller exponent. 46 Expressions similar to eq 4 will be used for the unfolding reaction (with A U , ∆G U / and η γ ) and the charge transfer reaction (with A CT , ∆G CT / , and η β ).…”

Section: Kinetic Analysis Of the Nonpolar Mechanismmentioning

confidence: 99%

Electron Transfer in a Flexible, Tethered Donor−Acceptor Pair: The Influence of Solute Conformation on Solvent-Dependent Free Energies

2004

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ADMA (1-(9-anthryl)-3-(4-dimethylanilino)propane) undergoes charge transfer following excitation of the anthryl moiety and forms an exciplex. Two mechanisms of charge transfer have been identified in previous work, and the operative mechanism depends on the polarity of the solvent. These are referred to as the nonpolar and the polar mechanisms. In polar solvents the charge transfer is rapid and occurs in an extended conformation followed by folding to form the exciplex. In hydrocarbons the exciplex formation rate is much slower and requires the donor and acceptor moieties to attain the correct geometry prior to charge transfer. Prior to the present work, it has been assumed that the charge transfer mechanism in hydrocarbons is diffusion controlled. In this work we demonstrate that charge transfer in nonpolar solvents is an activated process. We measure the rate of charge transfer in ethers (solvents of modest polarity with ) 3-4.3) and compare these to charge transfer rates in alkanes having similar viscosity. Whereas alkane charge transfer rates are well correlated to a viscosity power law, the rates in ethers are accelerated. We calculate the solvent-dependent driving force for the reaction using two different models, and the results also allow us to calculate the reaction reorganization energies. These are then used to estimate the activation barrier for the reaction, which demonstrate that the reaction is not encounter controlled. Analysis of the results demonstrates that solvent stabilization of the product state accelerates the charge transfer rate, in accord with Marcus theory, for solvents with dielectric constants between 2 and ∼4. Solvents with dielectric constants between 4 and 5 exhibit additional acceleration of the charge transfer reaction due to solvent dependence of the distance at which charge transfer occurs. This reflects a transition between the nonpolar and polar mechanisms.

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Section: Kinetic Analysis Of the Nonpolar Mechanismmentioning

confidence: 99%

Electron Transfer in a Flexible, Tethered Donor−Acceptor Pair: The Influence of Solute Conformation on Solvent-Dependent Free Energies

2004

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“…One useful approach to this problem is to change the pressure, where the pressure effect on the solvation structure is preferably small, yet the dynamical properties are markedly changed with a single probe molecule , Pressure causes the time scale of diffusive dynamics to be slower, so that the fast dynamics at atmospheric pressure may be shifted to slower and enables us to observe at high pressures with a longer well-detectable time scale. Furthermore, the high-pressure study may be useful for discriminating the diffusive process from nondiffusive (or inertial) relaxation process.…”

Section: Introductionmentioning

confidence: 99%

Pressure Effect on Solvation Dynamics in Micellar Environment

2001

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Solvation dynamics of an excited solvatochromic probe molecule in micellar environment has been studied as a function of pressure. In addition to steady-state spectrum, time-dependent fluorescence Stokes shift of coumarin 153 in aqueous solution of typical neutral surfactant Triton X-100 was measured at high pressures using time-correlated single-photon counting techniques with a time-resolution of 20 ps. It was found that polarity of the microenvironment decreases with increasing pressure. The solvation dynamics exhibits bimodal relaxation behavior with two characteristic time constants of 198 ps and 1.63 ns at atmospheric pressure. The solvation time becomes shorter with increasing pressure. The bimodal relaxation and its pressure dependence is considered as closely connected with the pressure effect on the hydrogen bonding of water molecules. And also the model assuming an equilibrium between "bound water" and "free water" within the Stern layer of micelles is discussed.

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“…We compare the results of the two previous studies 18,19 that measured the effect of hydrostatic pressure on solvation dynamics with the current one. The three studies used time-resolved emission techniques to measure the solvation dynamics of a fluorescent probe molecule in several monols from the smallchain ethanol to the long-chain 3-octanol.…”

Section: S(t) )mentioning

confidence: 93%

“…Hara and co-workers 19 studied the solvation dynamics of coumarin 153 in several alcohols, including propanol, butanol, and pentanol, as a function of pressure up to about 0.4 GPa. As in the Huppert and Rentzepis 18 study, they also found that the average solvation time correlates well with the longest longitudinal relaxation time.…”

Section: Introductionmentioning

confidence: 99%

Pressure Dependence of Solvation Dynamics of Coumarin 480 in Ethanol

2002

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The effect of the pressure on the solvation dynamics of coumarin 480 in ethanol has been studied by means of time-resolved emission using the time-correlated single-photon-counting technique with 20-ps resolution. The solvation dynamics slow with pressure. The pressure was varied from atmospheric pressure to about 1.8 GPa, the liquid−solid phase transition. At low pressures, <0.5 GPa, the solvation correlation function is nearly exponential, whereas, at pressures higher than about 0.5 GPa, it is nonexponential and can be fitted to a biexponential function whose short component is about 110 ps at pressures above 1 GPa. In the solid phase, solvation dynamics occurs at a relatively fast rate, similar to the liquid phase and at about the same pressure.

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Pressure Tuning of Solvent Relaxation Time for the Excited Intramolecular Charge-Transfer Kinetics in 4-(N,N-Dimethylamino)triphenylphosphine in Alcohol

Cited by 11 publications

References 30 publications

Electron Transfer in a Flexible, Tethered Donor−Acceptor Pair: The Influence of Solute Conformation on Solvent-Dependent Free Energies

Electron Transfer in a Flexible, Tethered Donor−Acceptor Pair: The Influence of Solute Conformation on Solvent-Dependent Free Energies

Pressure Effect on Solvation Dynamics in Micellar Environment

Pressure Dependence of Solvation Dynamics of Coumarin 480 in Ethanol

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