Dual phosphorescence of benzophenone at 77 K in the mixed solvent of 2,2,2-trifluoroethanol and water

Nakayama, Toshihiro; Sakurai, Kazumitsu; Ushida, Kiminori; Kawatsura, K.; Hamanoue, Kumao

doi:10.1016/0009-2614(89)85257-1

Cited by 15 publications

(9 citation statements)

References 11 publications

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“…Phosphorescence of AT, 2,3-MAT, 1,4-MAT, and 1,4-DMAT in 2,2,2- Trifluoroethanol (TFE). Although the specific interactions between triplet ketones and TFE are still controversial, broad spectra and longer lifetimes are indicative of a substantial increase in the π,π* character of T1. − The emission and decay of AT in TFE has dual character (Figure ). Spectra detected between 0 and 10 ms have an n,π* vibrational progression but are significantly broader than those observed in MCH and EtOH.…”

Section: Resultsmentioning

confidence: 99%

Effect of Solvents on the Photoenolization ofo-Methylanthrone at Low Temperatures. Evidence for H-Atom Tunneling from Nonequilibrating Triplets

Gamarnik

Johnson

1998

J. Phys. Chem. A

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The reactivity of 1,4-dimethylanthrone (1,4-MAT) and 1,4-dimethylanthrone-d 8 (1,4-DMAT) toward hydrogen transfer was investigated in methylcyclohexane (MCH), ethanol (EtOH), and 2,2,2-trifluoroethanol (TFE) by comparing their triplet-state emission spectra and lifetimes with those of compounds without the o-methyl substituent. A predominantly n,π* lowest triplet state in nonpolar solvents such as MCH changes toward a less reactive π,π* configuration in polar solvents such as EtOH and TFE. In EtOH, 1,4-DMAT exhibits a temperature-dependent dual emission while the corresponding protio compound (1,4-MAT) decays by reaction at all temperatures analyzed (ca. 15−90 K). Although compounds without the o-methyl group also presented dual emission, their relative intensities and lifetimes were shown to be temperature-independent, indicating the lack of thermal equilibration between the two triplets below 90 K. In the case of 1,4-DMAT in EtOH, an Arrhenius plot based on the data from the short-lived component (mainly n,π*) and detection of the enol between 19 and 80 K revealed that deuterium transfer occurs by quantum-mechanical tunneling (QMT). In agreement with results in MCH where a short-lived n,π* state predominates, the D-tunneling rate constant was estimated to be ca. (1.5−7.5) × 103 s-1. The phosphorescence of anthrone derivatives in TFE was long-lived, with a strong π,π* character, and highly heterogeneous, but not dual. A large isotope effect on phosphorescence is assigned to the isotope-dependent tunneling reaction from a predominant π,π* state.

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Section: Resultsmentioning

confidence: 99%

Effect of Solvents on the Photoenolization ofo-Methylanthrone at Low Temperatures. Evidence for H-Atom Tunneling from Nonequilibrating Triplets

Gamarnik

Johnson

1998

J. Phys. Chem. A

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“…Secondly, the increase in HFIP concentrations was accompanied by the disappearance of the typical "five-fingered" pattern of the n, * benzophenone chromophores. Similar types of changes in the phosphorescence spectrum of BP have also been observed in ethanol-water and trifluoroethanol (TFE)-water mixtures [11].…”

Section: Absorption and Emission Spectramentioning

confidence: 74%

“…In HFIP the decay was biexponential, with rate constant values of 135 s −1 and 45 s −1 . This kind of dual phosphorescence has already been reported for a few of the aromatic carbonyl compounds, including benzophenones [11,22,24]. Dual components in the phosphorescence decay indicate that the two emitting states (n, * and , * ) are populated and that the two states are not in thermal equilibrium at 77 K. Hamanoue et al [11] also observed the dual exponentiality of the phosphorescence decay of BP in TFE-water mixtures and assigned the shorter component (270 s −1 ) to the lowest triplet state of free benzophenone, with normal n, * character, and the long-lived (63 s −1 ) component to the lowest triplet state of a complex BP-H 2 O-TFE with mixed n, * /, * character.…”

Section: Absorption and Emission Spectramentioning

confidence: 91%

“…This kind of dual phosphorescence has already been reported for a few of the aromatic carbonyl compounds, including benzophenones [11,22,24]. Dual components in the phosphorescence decay indicate that the two emitting states (n, * and , * ) are populated and that the two states are not in thermal equilibrium at 77 K. Hamanoue et al [11] also observed the dual exponentiality of the phosphorescence decay of BP in TFE-water mixtures and assigned the shorter component (270 s −1 ) to the lowest triplet state of free benzophenone, with normal n, * character, and the long-lived (63 s −1 ) component to the lowest triplet state of a complex BP-H 2 O-TFE with mixed n, * /, * character. Based on the general nature of the phosphorescence spectrum and decay of the benzophenones, the phosphorescence observed in this work can be understood by assigning the lowest triplet state of BP in ACN to the n, * state but by assigning the lowest triplet state of BP in HFIP as having both , * and n, * character which, based on the data above, might be mixed or in thermal equilibrium (but see below).…”

Section: Absorption and Emission Spectramentioning

confidence: 91%

“…proposed that benzophenone forms complexes with water and TFE that may be of mixed n, * -, * character [11]. To our knowledge, there is no other report stating that the triplet state of unsubstituted benzophenone can possess other than pure n, * character.…”

Section: Methodsmentioning

confidence: 96%

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Unusual photobehavior of benzophenone triplets in hexafluoroisopropanol. Inversion of the triplet character of benzophenone

Lewandowska-Andrałojć

Hug

Hörner

et al. 2012

Journal of Photochemistry and Photobiology A: Chemistry

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Aggregation‐Induced Dual Phosphorescence from (o‐Bromophenyl)‐Bis(2,6‐Dimethylphenyl)Borane at Room Temperature

Dinkelbach

Kerner

et al. 2022

Chemistry A European J

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Designing highly efficient purely organic phosphors at room temperature remains a challenge because of fast non‐radiative processes and slow intersystem crossing (ISC) rates. The majority of them emit only single component phosphorescence. Herein, we have prepared 3 isomers (o, m, p‐bromophenyl)‐bis(2,6‐dimethylphenyl)boranes. Among the 3 isomers (o‐, m‐ and p‐BrTAB) synthesized, the ortho‐one is the only one which shows dual phosphorescence, with a short lifetime of 0.8 ms and a long lifetime of 234 ms in the crystalline state at room temperature. Based on theoretical calculations and crystal structure analysis of o‐BrTAB, the short lifetime component is ascribed to the T1M state of the monomer which emits the higher energy phosphorescence. The long‐lived, lower energy phosphorescence emission is attributed to the T1A state of an aggregate, with multiple intermolecular interactions existing in crystalline o‐BrTAB inhibiting nonradiative decay and stabilizing the triplet states efficiently.

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Dual phosphorescence of benzophenone at 77 K in the mixed solvent of 2,2,2-trifluoroethanol and water

Cited by 15 publications

References 11 publications

Effect of Solvents on the Photoenolization ofo-Methylanthrone at Low Temperatures. Evidence for H-Atom Tunneling from Nonequilibrating Triplets

Effect of Solvents on the Photoenolization ofo-Methylanthrone at Low Temperatures. Evidence for H-Atom Tunneling from Nonequilibrating Triplets

Unusual photobehavior of benzophenone triplets in hexafluoroisopropanol. Inversion of the triplet character of benzophenone

Aggregation‐Induced Dual Phosphorescence from (o‐Bromophenyl)‐Bis(2,6‐Dimethylphenyl)Borane at Room Temperature

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