Deactivation of benzophenone triplets via exciplex formation. Evidence for dual reaction pathways

Wolf, Monte W.; Brown, Ronald E.; Singer, Lawrence A.

doi:10.1021/ja00444a036

Cited by 85 publications

(49 citation statements)

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“…This conclusion had been drawn earlier by a number of workers. [13][14][15] Shizuka et al [14] termed the reaction "induced quenching". Notably, this quenching pathway appears to be efficient since no transient products of the BP triplet quenching by anisole have ever been observed, even in the polar solvent acetonitrile (ACN) or in ACN/water mixtures.…”

Section: Introductionmentioning

confidence: 99%

Efficient Photochemical Oxidation of Anisole in Protic Solvents: Electron Transfer driven by Specific Solvent–Solute Interactions

et al. 2010

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The dynamics of the bimolecular quenching of triplet excited benzophenone by anisole was studied by nanosecond flash photolysis. We carried out a detailed study of the solvent dependence of the reaction rates and efficiencies in a number of protic and non-protic solvents. These studies were augmented by theoretical modelling and experimental investigation of solute/solvent interactions in the triplet excited and the ground state, respectively. The triplet quenching that follows Stern-Volmer kinetics in all cases is profoundly dependent on the nature of the solvent, with the highest reactivity being consistently found in protic solvents. The results in non-protic solvents are compatible with unproductive quenching via a charge-transfer state, whereas the generally fast quenching in protic solvents is accompanied by efficient formation of free-radical products. Analysis of the solvent dependence in terms of Marcus theory reveals the impact of specific solvation of benzophenone by protic solvents on the ET driving force and kinetics. Specific solvation is found to support efficient free radical ion formation in media of moderate and low polarity as well.

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Section: Introductionmentioning

confidence: 99%

Efficient Photochemical Oxidation of Anisole in Protic Solvents: Electron Transfer driven by Specific Solvent–Solute Interactions

et al. 2010

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“…¹1 s ¹1 and 53.9¯s, respectively. The lifetime was longer than that of the 3 nπ* state of 3 2, i.e., 6.9¯s in benzene, 16 but significantly shorter than the characteristic triplet lifetime of the planar 3 ππ* triplet state, 3 3, whose lifetime is known to be 500¯s in benzene and 100¯s in acetonitrile. 17 The significantly shorter lifetime of the triplet species 3 1 than of the planar 3 3 is rationalized by the curved π-system in mechanism.…”

mentioning

confidence: 82%

Intra- and Intermolecular Reactivity of Triplet Sumanenetrione

Kanahara

Badal

Hatano

et al. 2015

Bulletin of the Chemical Society of Japan

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The intra-and intermolecular reactivity of triplet sumanenetrione 3 1, which contains a curved π-system, were investigated to characterize the triplet aromatic ketone. The lowest ππ* triplet energy and lifetime were determined from phosphorescence measurements at 77 K to be 196 kJ mol ¹1 and 9.5 ms in methylcyclohexane, respectively. The transient ππ* triplet state 3 1 was detected by laser flash photolysis at 293 K and found to be significantly short-lived, e.g., 53.9¯s in degassed benzene, compared to a planar ππ* triplet ketone such as fluorenone triplet (500¯s). The fast intersystem crossing process (ISC) of 3 1 was attributed to the curved structure of the sumanenetrione, which enhances spin-orbit coupling (SOC). The ππ* character was proven by its negligible quenching by isopropanol, i.e., k q < 4.50 © 10 3 M ¹1 s ¹1, although the quenching rate constants for molecular oxygen and triethylamine in benzene were high: 1.0 © 10 9 M ¹1 s ¹1 and 4.0 © 10 8 M ¹1 s ¹1 . The ππ* character of the triplet state was also proven by the relatively small electron spin resonance zero-field splitting parameter, «D«/hc, in toluene at 78 K, which was found to be 0.0621 cm ¹1. The «E«/hc parameter was determined to be 0.0071 cm ¹1 .

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“…The quenching of this triplet by a phenyl group was proposed to proceed through an exciplex formation between the excited triplet state of benzophenone and n-orbital of the phenyl group. 21 The quenching rate constant of benzophenone triplet by polystyrene in solution was found to be 1.2 x 10 6 unit-M-1 s-1 in benzene 22 and 4.0 x 10 6 unit-M-1 s-1 in acetonitrile23 at 30°C. Thus, the dynamic quenching of benzophenone triplet by the side-chain phenyl group in polystyrene or by the main-520 chain phenylene group in PBA-PC should cause the deviation in the phosphorescence decay from a single exponential type.…”

Section: Temperature Dependence Of the Decay Curvesmentioning

confidence: 95%

Photochemistry in Polymer Solids V. Decay of Benzophenone Phosphorescence in Polystyrene and in Polycarbonate

Horie

Tsukamoto

Morishita

et al. 1985

Polym J

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ABSTRACT:Decay curves and lifetimes of benzophenone phosphorescence in polystyrene and in bisphenol A polycarbonate (BPA-PC) at 80----433 K significantly reflect change in the molecular motion of matrix polymers such as glass transition, /3-transition, and }'-transition. The non-singleexponential decay. curves were observed in both polymers at temperatures between T, and T., and analyzed using the diffusion-controlled rate coefficient with a time dependent transient term for the dynamic quenching process of benzophenone triplet by phenyl or phenylene groups in the matrix polymers. The diffusion coefficients, D, of the reacting functional groups in polystyrene and BPA-PC for the wide temperature range below T. are much larger than that in PMMA in the same temperature range, showing a higher quenching ability of these polymers for the benzophenone triplet.

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Deactivation of benzophenone triplets via exciplex formation. Evidence for dual reaction pathways

Cited by 85 publications

References 1 publication

Efficient Photochemical Oxidation of Anisole in Protic Solvents: Electron Transfer driven by Specific Solvent–Solute Interactions

Efficient Photochemical Oxidation of Anisole in Protic Solvents: Electron Transfer driven by Specific Solvent–Solute Interactions

Intra- and Intermolecular Reactivity of Triplet Sumanenetrione

Photochemistry in Polymer Solids V. Decay of Benzophenone Phosphorescence in Polystyrene and in Polycarbonate

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