Photophysical studies on the benzophenones. Prompt and delayed fluorescences and self-quenching

Wolf, Monte W.; Legg, Kenneth D.; Brown, Ronald E.; Singer, Lawrence A.; Parks, Joel H.

doi:10.1021/ja00849a008

Cited by 94 publications

(60 citation statements)

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“…Due to the efficient ISC deactivation of the singlet state, relaxation of excess energy on the triplet manifold has been observed generally for various aromatic carbonyls in the solution phase, and our results here are consistent with these other observations. [74][75][76][77] In summary, we suggest the following nonradiative pathway for the 267 nm photoexcitation of HPA and HPDP in solvent:…”

Section: Isc Mechanism and Deactivation Of The Excited Statesmentioning

confidence: 90%

Ultrafast Time-Resolved Study of Photophysical Processes Involved in the Photodeprotection of p-Hydroxyphenacyl Caged Phototrigger Compounds

et al. 2005

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A combined femtosecond Kerr gated time-resolved fluorescence (fs-KTRF) and picosecond Kerr gated time-resolved resonance Raman (ps-KTR(3)) study is reported for two p-hydroxyphenacyl (pHP) caged phototriggers, HPDP and HPA, in neat acetonitrile and water/acetonitrile (1:1 by volume) solvents. Fs-KTRF spectroscopy was employed to characterize the spectral properties and dynamics of the singlet excited states, and the ps-KTR(3) was used to monitor the formation and subsequent reaction of triplet state. These results provide important evidence for elucidation of the initial steps for the pHP deprotection mechanism. An improved fs-KTRF setup was developed to extend its detectable spectral range down to the 270 nm UV region while still covering the visible region up to 600 nm. This combined with the advantage of KTRF in directly monitoring the temporal evolution of the overall fluorescence profile enables the first time-resolved observation of dual fluorescence for pHP phototriggers upon 267 nm excitation. The two emitting components were assigned to originate from the (1)pipi (S(3)) and (1)npi (S(1)) states, respectively. This was based on the lifetime, the spectral location, and how these varied with the type of solvent. By correlating the dynamics of the singlet decay with the triplet formation, a direct (1)npi --> (3)pipi ISC mechanism was found for these compounds with the ISC rate estimated to be approximately 5 x 10(11) s(-)(1) in both solvent systems. These photophysical processes were found to be little affected by the kind of leaving group indicating the common local pHP chromophore is largely responsible for the fluorescence and relevant deactivation processes. The triplet lifetime was found to be approximately 420 and 2130 ps for HPDP and HPA, respectively, in the mixed solvent compared to 150 and 137 ns, respectively, in neat MeCN. The solvent and leaving group dependent quenching of the triplet is believed to be associated with the pHP deprotection photochemistry and indicates that the triplet is the reactive precursor for pHP photorelease reactions for the compounds examined in this study.

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Section: Isc Mechanism and Deactivation Of The Excited Statesmentioning

confidence: 90%

Ultrafast Time-Resolved Study of Photophysical Processes Involved in the Photodeprotection of p-Hydroxyphenacyl Caged Phototrigger Compounds

et al. 2005

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“…3 For a given fluorophore, TADF is usually much weaker than its PF. Although known for many years, TADF continues to be a rare phenomenon, with a few observations in some xanthene dyes, 1,4,5 aromatic ketones 6,7 and thiones, 8,9 metal porphyrins, 10 and aromatic hydrocarbons. [11][12][13] The remarkable photophysical properties of fullerene C 70 , specifically the ⌽ T very close to one, the small ⌬E ST gap and the long intrinsic phosphorescence lifetime, lead to the discovery of an exceptionally strong TADF in this molecule.…”

Section: Introductionmentioning

confidence: 99%

Thermally activated delayed fluorescence as a cycling process between excited singlet and triplet states: Application to the fullerenes

Baleizão¹,

Berberan‐Santos²

2007

The Journal of Chemical Physics

115

152

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In efficient thermally activated delayed fluorescence (TADF) the excited chromophore alternates randomly between the singlet and triplet manifolds a large number of times before emission occurs. In this work, the average number of cycles n is obtained and is shown to have a simple experimental meaning: n+1 is the intensification factor of the prompt fluorescence intensity, owing to the occurrence of TADF. A new method of data analysis for the determination of the quantum yield of triplet formation, combining steady-state and time-resolved data in a single plot, is also presented. Application of the theoretical results to the TADF of [70]fullerenes shows a general good agreement between different methods of fluorescence analysis and allows the determination of several photophysical parameters.

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“…selfquenching) in aqueous solution. In the case of benzophenone itself, the lifetime of the triplet state can be drastically affected by this type of deactivating interaction (6)(7)(8)(9)(10)(11). However, while these processes are relatively well understood in organic solvents, the same does not hold in the case of aqueous solution (6, 7, 1 l ) , where the roles played by T-T annihilation and self-quenching are still subject to controversy.…”

Section: Introductionmentioning

confidence: 99%

New functionalized water-soluble benzophenones: a laser flash photolysis study

Lougnot¹,

Jacques²,

Fouassier³

et al. 1985

Can. J. Chem.

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Two water-soluble ionic benzophenones containing a quatemized amine and a sulphonate group have been investigated by laser flash photolysis. The decay kinetics and spectra of their triplet states were studied and quenching constants by triethanolamine, isopropanol, and methyl viologen determined. These data are of interest when these benzophenones are used as initiators for photo-polymerizing water-soluble acrylates in homogeneous solution or in reverse micellar assemblies. The high water solubility of these compounds allows the bimolecular deactivations due to triplet–triplet (kTT) and triplet–ground state (kSQ) interactions to be determined more accurately than in the case of benzophenone itself.

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Photophysical studies on the benzophenones. Prompt and delayed fluorescences and self-quenching

Cited by 94 publications

References 1 publication

Ultrafast Time-Resolved Study of Photophysical Processes Involved in the Photodeprotection of p-Hydroxyphenacyl Caged Phototrigger Compounds

Ultrafast Time-Resolved Study of Photophysical Processes Involved in the Photodeprotection of p-Hydroxyphenacyl Caged Phototrigger Compounds

Thermally activated delayed fluorescence as a cycling process between excited singlet and triplet states: Application to the fullerenes

New functionalized water-soluble benzophenones: a laser flash photolysis study

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