Effect of solvent on excited-state intramolecular proton transfer in benzotriazole photostabilizers

Ghiggino, K. P.; Scully, Andrew D.; Leaver, Ian H.

doi:10.1021/j100412a042

Cited by 82 publications

(49 citation statements)

References 1 publication

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“…This result disagrees with the standard paradigm for benzotriazole UVAs, which predicts that the loss of the hydrogen bond will lead to the onset of significant fluorescence. 10,20 The methyl ethers 11 and 12, neither of which possess an intramolecular hydrogen bond, both display reduced fluorescence in DMSO as compared to hexanes (see Figure 4). In addition, the fluorescence is strongly red shifted.…”

Section: Resultsmentioning

confidence: 99%

“…Compound 1 has a very efficient pathway for deactivation of S 1 so that other excited state processes [i.e., intersystem crossing (ISC), fluorescence, photoreaction] are unable to compete (see Scheme 1). 4,5 The mechanism of fluorescence deactivation of 1 and related compounds has been the focus of several studies, [5][6][7][8][9][10][11][12] whose findings have converged on an excited state intramolecular proton transfer mechanism (ESIPT) of fluorescence deactivation. This mechanism is illustrated in Scheme 1.…”

Section: Introductionmentioning

confidence: 99%

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Twisted Intramolecular Charge Transfer States in 2-Arylbenzotriazoles: Fluorescence Deactivation via Intramolecular Electron Transfer Rather Than Proton Transfer

et al. 2002

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Ultraviolet absorbers such as Tinuvin P (2-(2-hydroxy-5-methylphenyl)benzotriazole), 1, achieve their exceptional photostabilities as a result of deactivation of excited singlet states through excited state intramolecular proton transfer (ESIPT). Adding a methyl group to the 6′ position of 2-arylbenzotriazoles reveals an additional excited singlet state deactivation mechanism in this class of molecules which does not require intramolecular hydrogen bonding. Steady state fluorescence and fluorescence lifetime measurements for a series of 6′-methyl-2-arylbenzotriazoles provides compelling evidence for a twisted intramolecular charge transfer (TICT) mechanism of excited singlet state deactivation. Due to the steric requirements of the 6′-methyl group, conformations are favored in which the phenyl and triazole rings are no longer coplanar. In the case of compound 11 (2-(6-methoxy-2,3-dimethylphenyl)-2H-benzotriazole), the presence of a 2′-methoxy group enhances nonplanarity and results in large deactivation rates. Compound 12 (2-(6-methoxy-2,3-dimethylphenyl)-5-(trifluoromethyl)-2H-benzotriazole), which possesses both twist and enhanced donor/acceptor properties, undergoes the most efficient fluorescence quenching for the methoxyarylbenzotriazoles. Compounds with both a 6′-methyl and a hydroxy group on the phenyl ring exhibit diffusion controlled quenching (k q ) 2 × 10 10 M -1 s -1) by DMSO. This quenching appears to result from either partial or complete excited state proton transfer to DMSO, which enhances TICT deactivation of the singlet excited state.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Twisted Intramolecular Charge Transfer States in 2-Arylbenzotriazoles: Fluorescence Deactivation via Intramolecular Electron Transfer Rather Than Proton Transfer

et al. 2002

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“…Excited state intramolecular proton transfer (ESIPT) is an interesting phenomenon that has been studied for a long time [1][2][3][4][5][6][7][8][9][10][11]. It is a well known that in an excited state, a molecule can undergo structural changes and can assume a different geometry due to significant charge redistribution [12], thereby greatly changing the excited state's properties.…”

Section: Introductionmentioning

confidence: 99%

Understanding the photophysics of 4-nitro-1-hydroxy-2-naphthoic acid: A controlled excited state proton transfer

Sahoo

Adhikary²,

Chowdhury³

et al. 2008

Chemical Physics

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“…All these observations cast serious doubt on the reliable prediction of any kind of equilibrium reactions, and lend strong support to the benefits of their experimental determination. Important applications, such as use of proton transfer equilibrium in sensing interfacial proton concentration of microheterogeneous media (32)(33)(34) and use of phototautomers as effective light protectors and materials in continuous lasers, have surfaced (35)(36)(37). Another aspect of acidity and basicity dependence that becomes especially important is evident when absorption and fluorescence probing of organized assemblies is done by externallinternal probes that Can.…”

Section: Introductionmentioning

confidence: 99%

Proton transfer equilibrium reactions in some substituted 3H-indole probe molecules: role played by the TICT state

Sarpal¹,

Belletête²,

Durocher³

1993

Can. J. Chem.

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(6). The dependence of absorption and fluorescence spectral characteristics upon acidity has allowed us to characterize four species, namely, the anion (A), the neutral molecule (N), the cation (C), and the dication (DC), for molecules 2 and 3 . Molecules 4, 5, and 6 give rise to an additional anion due to the hydrolysis of the ester group. The relative order of protonations to available sites is discussed. The ring-protonated species have shown the Ph, and indole rings to be coplanar in both the ground and first excited singlet states. A low-energy non-emissive twisted intramolecular charge transfer (TICT) state taking its origin in the dimethylamino moiety is suggested from INDO-S calculations to explain the strong fluorescence quenching of these ring-protonated species. Acidity constants for the various prototropic equilibria have been determined experimentally both in the ground and in the excited singlet states. Forster cycle calculations have been used to supplement the various equilibrium constants. Possible applications in organized assemblies are discussed. additionnel qui provient d'une hydrolyse de l'ester. On discute de I'ordre relatif des protonations des divers sites. On a dCmontrC que les espbces protonCes des cycles benzenique et indolique sont coplanaires tant dans 1'Ctat fondamental que dans le premier Ctat excitC. Sur la base de calculs INDO-S, on suggbre qu'un Ctat de transfert de charge intramolCculaire dCformC, de basse Cnergie, non radiatif et dont I'origine se trouverait dans la portion dimCthylamino peut expliquer la forte dksactivation de fluorescence de ces espbces protonkes sur le cycle. On a dCterminC experimentalement les constantes d'aciditt des divers Cquilibres prototropiques tant dans 1'Ctat fondamental que dans les Ctats excites. On a utilisC des calculs de cycles de Forster comme supplCments aux diverses constantes d'kquilibre. On discute de diverses applications possibles pour des systbmes organises.[Traduit par la rCdaction]

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Effect of solvent on excited-state intramolecular proton transfer in benzotriazole photostabilizers

Cited by 82 publications

References 1 publication

Twisted Intramolecular Charge Transfer States in 2-Arylbenzotriazoles: Fluorescence Deactivation via Intramolecular Electron Transfer Rather Than Proton Transfer

Twisted Intramolecular Charge Transfer States in 2-Arylbenzotriazoles: Fluorescence Deactivation via Intramolecular Electron Transfer Rather Than Proton Transfer

Understanding the photophysics of 4-nitro-1-hydroxy-2-naphthoic acid: A controlled excited state proton transfer

Proton transfer equilibrium reactions in some substituted 3H-indole probe molecules: role played by the TICT state

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