Picosecond Dynamics of Nonadiabatic Proton Transfer:  A Kinetic Study of Proton Transfer within the Contact Radical Ion Pair of Substituted Benzophenones/<i>N</i>,<i>N</i>-Dimethylaniline

Peters, Kevin S.; Cashin, and Amanda; Timbers, Peter

doi:10.1021/ja991604+

Cited by 62 publications

(91 citation statements)

References 43 publications

(68 reference statements)

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“…64 They obtained a H-bond energy of 2.6 kcal/mol for the formic acid-formic acid complex and 7.2 kcal/mol for the formic acid-formate anion complex. This estimate is in reasonable agreement with the activation energy for proton exchange between maleic acid and hydrogen maleate in 10% water/acetone-d 6 , which is consistent with a ca. 4 kcal/mol stronger intermolecular H-bond in the hydrogen maleate than the conventional H-bond in aqueous solution.…”

Section: Introductionsupporting

confidence: 86%

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Absolute Rate Calculations. Proton Transfers in Solution

2007

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The reaction path of the intersecting-state model is used in transition-state theory with the semiclassical correction for tunneling (ISM/scTST) to calculate the rates of proton-transfer reactions from hydrogen-bond energies, reaction energies, electrophilicity indices, bond lengths, and vibration frequencies of the reactive bonds. ISM/scTST calculations do not involve adjustable parameters. The calculated proton-transfer rates are within 1 order of magnitude of the experimental ones at room temperature, and cover very diverse systems, such as deprotonations of nitroalkanes, ketones, HCN, carboxylic acids, and excited naphthols. The calculated temperature dependencies and kinetic isotope effects are also in good agreement with the experimental data. These calculations elucidate the roles of the reaction energy, electrophilicity, structural parameters, hydrogen bonds, tunneling, and solvent in the reactivity of acids and bases. The efficiency of the method makes it possible to run absolute rate calculations through the Internet.

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Section: Introductionsupporting

confidence: 86%

“…112 This has been interpreted as an example of an "inverted region", 6,7,88 and it was rationalized in terms of a nonadiabatic model. However, this "inverted region" is much less pronounced than the "nitroalkane anomaly", where the PT rate decreases by a factor of 100 for the same decrease in ∆G 0 .…”

Section: Solvent Effectsmentioning

confidence: 99%

Absolute Rate Calculations. Proton Transfers in Solution

2007

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“…In the second step, proton transfer takes place to give a triplet radical pair 3 [ , ] . This reaction was observed experimentally by picosecond photolysis in a study on the photoinduced reduction of a series of benzophenones in the presence of N , N -dimethylaniline [4,5]. The existence of two steps in the hydrogen-transfer reaction suggests that the overall rate of the photoinduced reduction may be limited by both electron-transfer and proton-transfer steps.…”

mentioning

confidence: 91%

Kinetic Isotope Effect in the Photoreduction of o-Benzoquinones in the Presence of N,N-Dimethylaniline

et al. 2005

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The kinetics of photoinduced reduction of a series of 3,5-and 3,6-di-tert -butylbenzoquinones-1,2 was studied in the presence of N , N -dimethylaniline, its deuterated analog, and a series of para -substituted N , Ndimethylanilines. On passing from the endothermic to the exothermic range of the free energy of electron transfer ∆ G e , the effective rate constants k H and k D and the quantum yields ϕ H and ϕ D of the reaction varied nonmonotonically with a maximum at ∆G e of approximately +0.1 eV. For the reactant pairs relevant to the ascending (left-hand) branch of the plot k H = f(∆G e ), the H/D isotope effect takes place, varying from two to five in magnitude. For the reactant pairs at the maximum and in the descending (right-hand) branch of the plot k H = f(∆G e ), there is no isotope effect or its value is insignificant.

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“…Direct proofs for the stepwise character of the photoreduction were obtained from the picosecond photolysis study of the "classical" system benzophenone-N,N dimethylaniline (BP-DMA). 21, 22 This mechanism of hydrogen transfer for the photoreduction of carbonyl containing compounds was proposed and discussed in earlier studies. 6,15,18,19, 23 It seems reasonable to consider a relation between the kinetic parameters of photoreduction and ∆G e due to the presence of an electron transfer step.…”

Section: Resultsmentioning

confidence: 88%

Kinetics of photoreduction of 9,10-phenanthrenequinone in the presence of amines and polymethylbenzenes

et al. 2004

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A study of the kinetics of photoreduction of 9,10 phenanthrenequinone in the presence of hydrogen donors (para substituted N,N dimethylanilines and polymethylbenzenes) showed that plots of the quantum yield of photoreduction (ϕ H ) and apparent reaction rate constant (k H ) vs. oxidation potential of hydrogen donors are extreme. In the presence of amines, k H and ϕ H increase, as a whole, whereas they decrease in the presence of polymethylbenzenes. In coordinates ϕ H -∆G e (∆G e is the change in the free energy of electron transfer) for pairs quinone-H donor, ϕ H increases with ∆G e approaching to zero. For the amine series, this effect is mainly in the exothermic region of ∆G e (∆G e < 0). For the series of polymethylbenzenes, this increase is observed in the endothermic region (∆G e > 0).

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Picosecond Dynamics of Nonadiabatic Proton Transfer: A Kinetic Study of Proton Transfer within the Contact Radical Ion Pair of Substituted Benzophenones/N,N-Dimethylaniline

Cited by 62 publications

References 43 publications

Absolute Rate Calculations. Proton Transfers in Solution

Absolute Rate Calculations. Proton Transfers in Solution

Kinetic Isotope Effect in the Photoreduction of o-Benzoquinones in the Presence of N,N-Dimethylaniline

Kinetics of photoreduction of 9,10-phenanthrenequinone in the presence of amines and polymethylbenzenes

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