Effect of high pressure on intramolecular electron-transfer luminescence of 9,9'-bianthryl in different solvents

Hara, Kimihiko; Arase, Takuya; Osugi, Jiro

doi:10.1021/ja00319a012

Cited by 49 publications

(26 citation statements)

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“…It is characterized by a small activation energy barrier (Ea << kBT, the product of the Boltzmann constant and absolute temperature) and by adiabaticity of the reaction mechanism, which may be the reason why its rate depends upon the dynamics of the solvent. For bianthryl, this rate, kCT, strongly correlates with the microscopic relaxation time of the solvent, which was determined by the fluorescent probe method (20) and depends strongly on the parameters on which the relaxation time depends: the temperature (24) and pressure (26,30). The correlation observed in our experiments between the temperature-dependent relaxational shifts of the CT form and its relative concentration is in accord with these findings.…”

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confidence: 86%

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Solvent reorganizational red-edge effect in intramolecular electron transfer.

Demchenko

Sytnik

1991

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

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Polar solvents are characterized by statistical distributions of solute-solvent interaction energies that result in inhomogeneous broadening of the solute electronic spectra. This allows photoselection of the high interaction energy part of the distribution by excitation at the red (long-wavelength) edge of the absorption bands. We observe that intramolecular electron transfer in the bianthryl molecule from the locally excited (LE) to the charge-transfer (CT) state, which requires solvent relaxation and does not occur in vitrified polar solutions, is dramatically facilitated in low-temperature propylene glycol glass by the red-edge excitation. This allows one to obtain spectroscopically the pure CT form and observe its dependence upon the relaxational properties of the solvent. A qualitative potential model of this effect is presented.Charge-transfer (CT) reactions in polar solvents are different from those in the gas phase. Their rates depend upon the solvent and in many cases can be correlated with such solvent parameters as electronic and nuclear polarizabilities, dipole moments, and relaxation rates (1-3). One can observe the inhomogeneity of reaction kinetics, which is expected to be very important for reactions on surfaces (4) in microheterogeneous media: micelles, microemulsions, and protein molecules (5, 6). Many important questions, however, remain unresolved. What is the dimensionality of the solvent coordinates? Can the solvents be characterized as homogeneous media and thermal baths only? If the solvent-derived inhomogeneity exists, is it static or dynamic in the sense that averaging of local states and interactions occurs faster or slower than the characteristic time of the reaction? Is the solvation of the reactant always at equilibrium in the course of the reaction? What is the nature of the control of reaction rate by the solvent dynamics? Is it controlled by its relaxational motions towards equilibrium, or is it dependent on frictional resistance of the already equilibrated solvent? The analysis of CT reactions in the excited state proves to be advantageous in resolving these problems for several reasons. There is a possibility of starting the reaction by a light pulse and observing its kinetics in real time (7,8). Similar time-resolved experiments can be used to study dipolerelaxational solvent dynamics (8, 9), and the site selectivity also can be easily achieved by excitation at selective wavelengths within inhomogeneously broadened absorption bands (10-12).Inhomogeneous broadening is known to be a significant contribution to the broadening of electronic spectra in polar solutions due to the distribution of solute-solvent interaction energies of a chromophore in different local environments (6,(10)(11)(12)(13)(14)(15). This results in a number of effects, which can be classified as either static (and observed in the steady-state spectra) or dynamic (and detectable in time-resolved experiments) (16,17). Static effects of inhomogeneous broadening are observed in solid and viscous solutio...

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confidence: 86%

“…The polar character of the CT state was demonstrated by the dependence of its fluorescence spectrum on solvent polarity in a series of liquid solvents (18,24,30). It is confirmed in our study while temperature-dependent shifts of the pure CT form are observed.…”

supporting

confidence: 84%

Solvent reorganizational red-edge effect in intramolecular electron transfer.

Demchenko

Sytnik

1991

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

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“…Activation Volume and Activation Energy in the Kinetically Controlled Regime. By the differentiation of eq 5 with respect to pressure, we obtain (7) By definition, differentiation of kl with respect to pressure gives the apparent activation volume, which is written by (a In kd aP) = -AV,b:/RT, where AV,b? represents the observed activation volume.…”

Section: Rate Of Tictmentioning

confidence: 99%

High-pressure studies of the viscosity effects on the formation of the twisted intramolecular charge-transfer (TICT) state in 4,4'-diaminodiphenyl sulfone (DAPS)

Bulgarevich¹,

Kajimoto²,

Hara³

1995

J. Phys. Chem.

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To investigate the dynamic solvent effects on the formation of the "twisted intramolecular charge-transfer (TICT)" state, the pressure as well as temperature effects on the fluorescence spectra of 4,4'-diaminodiphenyl sulfone (DAPS) in alcohol solvents were examined. It is concluded that solvent viscous friction makes an important contribution to the rate of TICT-state formation of DAPS in alcohols. The contribution of the dynamic solvent effect on the kinetics is well-separated from that of the intrinsic static contribution defined by transition-state theory (TST). The contribution of the solvation effect to the activation volume and activation energy of the TICT-state formation is also discussed.

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“…[2][3][4][5] Contrary to the early expectation, 3 it has recently been reported that no simple correlation between the TICT-state formation rate and solvent viscosity has been observed for the case of DMABN in a series of polar solvents with different viscosity. 6,7 By using a high-pressure method, we have been studying the influence of solvent viscosity on various barrier crossing processes involving large amplitude twisting conformational changes due to bulky aromatic groups such as TICT-state formation, 8,9 intramolecular excimer formation, 10 and photoisomerization. 11,12 In particular, the observation of a weak dependence of the barrier crossing rate on solvent viscosity has been discussed.…”

Section: Introductionmentioning

confidence: 99%

High-Pressure Studies on the Excited-State Intramolecular Charge Transfer of 4-(N,N-Dimethylamino)triphenylphosphine in Alcohols

1996

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The influence of solvent viscosity on the intramolecular charge-transfer (CT)-state formation in the excited S 1 state for 4-(N,N-dimethylamino) triphenylphosphine (DMATP) in alcohol solvents has been investigated by measuring the steady-state and time-resolved fluorescence spectra at high pressures. The kinetic mechanism of the intramolecular CT reaction has been examined as a function of solvent shear viscosity. In the lower viscosity region the reaction is controlled by the solvent relaxation. With increasing pressure, the reaction path shifts toward the "high-viscosity regime" in which the molecule moves along the nonrelaxed path on the free energy surface. The viscosity dependence of R = 0.33, where R is the power law parameter, can be interpreted as the extreme value in which the reaction is controlled by the dynamic solvent effect due to intrinsic collisional interaction of barrier crossing. The coupling between the intramolecular CT-state formation dynamics of DMATP and the solvent relaxation dynamics is discussed.

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Effect of high pressure on intramolecular electron-transfer luminescence of 9,9'-bianthryl in different solvents

Cited by 49 publications

References 0 publications

Solvent reorganizational red-edge effect in intramolecular electron transfer.

Solvent reorganizational red-edge effect in intramolecular electron transfer.

High-pressure studies of the viscosity effects on the formation of the twisted intramolecular charge-transfer (TICT) state in 4,4'-diaminodiphenyl sulfone (DAPS)

High-Pressure Studies on the Excited-State Intramolecular Charge Transfer of 4-(N,N-Dimethylamino)triphenylphosphine in Alcohols

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