Proton Phototransfers in Doubly Hydrogen Bonded Dimers: The Photophysics of 6,7,8,9-Tetrahydro-5<i>H</i>-pyrido[2,3-<i>b</i>]indole Dimers

Catalán, Javier

doi:10.1021/jp908770p

Cited by 6 publications

(3 citation statements)

References 34 publications

(77 reference statements)

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“…Upon excitation of the 7-azaindole dimer or complexes, a double proton transfer in the cyclic complex leads to deprotonation of the pyrrole NH group and protonation of the pyridine N. [11][12][13][49][50][51][52][53] Similar processes were observed for structurally related molecules, as for example 1-azacarbazole [11][12][13] and 1H-Pyrazolo [3,4b]quinoline. 54 For 6,7,8,9-tetrahydro-5H-pyrido [2,3-b]indole, a single proton transfer was observed in the dimer, 55 whereas only ground-state dimerization without excited-state proton transfer was observed for 9H-imidazo[1,2-a]benzimidazole. 56 The complex features displayed by molecules with some similarities to 1 anticipate the difficulty of understanding its excited-state behavior.…”

Section: Introductionmentioning

confidence: 99%

Photoinduced Proton and Charge Transfer in 2-(2′-Hydroxyphenyl)imidazo[4,5-b]pyridine

et al. 2013

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This paper deals with the interplay between solvent properties and isomerism of 2-(2'-hydroxyphenyl)imidazo[4,5-b]pyridine (1), and the proton and charge-transfer processes that the different isomers undergo in the first-excited singlet state. We demonstrate the strong influence of these processes on the fluorescence properties of 1. We studied the behavior of 1 in several neutral and acidified solvents, by UV-vis absorption spectroscopy and by steady-state and time-resolved fluorescence spectroscopy. The fluorescence of 1 showed a strong sensitivity to the environment. This behavior is the result of conformational and isomeric equilibria and the completely different excited-state behavior of the isomers. For both neutral and cationic 1, isomers with intramolecular hydrogen bond between the hydroxyl group and the benzimidazole N undergo an ultrafast excited-state intramolecular proton transfer (ESIPT), yielding tautomeric species with very large Stokes shift. For both neutral and cationic 1, isomers with the OH group hydrogen-bonded to the solvent behave as strong photoacids, dissociating in the excited state in solvents with basic character. The pyridine nitrogen exhibits photobase character, protonating in the excited state even in some neutral solvents. An efficient radiationless deactivation channel of several species was detected, which we attributed to a twisted intramolecular charge-transfer (TICT) process, facilitated by deprotonation of the hydroxyl group and protonation of the pyridine nitrogen.

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Section: Introductionmentioning

confidence: 99%

Photoinduced Proton and Charge Transfer in 2-(2′-Hydroxyphenyl)imidazo[4,5-b]pyridine

et al. 2013

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“…In 1956, Weller first observed excited-state intramolecular proton transfer (ESIPT) in methyl salicylate (MS). , Since then, though many works have been performed on proton transfer (PT) processes using various proton transfer probes − in the last few decades, but studies on the photophysical behavior of 1′-hydroxy-2′-acetonaphthone (HAN), which has potential ability in polymer protection, are limited. Furthermore, the application of ESIPT reactions for the development of white-light-emitting diodes, photostabilizers, proton transfer lasers, etc.…”

Section: Introductionmentioning

confidence: 99%

Photophysics and Photodynamics of 1′-Hydroxy-2′-acetonaphthone (HAN) in Micelles and Nonionic Surfactants Forming Vesicles: A Comparative Study of Different Microenvironments of Surfactant Assemblies

et al. 2011

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The effect of different microenvironments inside various biomimicking supramolecular assemblies of ionic (SDS/CTAB) and nonionic (TX100) micelles and nonionic surfactants (Tween-80/PEG-6000) forming vesicles (niosome) on the photophysical and rotational dynamical properties of 1'-hydroxy-2'-acetonaphthone (HAN) have been studied using steady-state and time-resolved fluorescence spectroscopy. Enhanced fluorescence intensity with a significant blue shift and longer emission lifetime of the caged tautomers of HAN indicate modulation of photophysics of HAN upon encapsulation in both micellar assemblies and the niosome system. The binding constant and free energy change for the complexation of HAN with micelles and niosome demonstrate a comparative study on the binding efficiency of the different assemblies depending on the nature of microenvironments toward HAN. The enhancement in the steady-state anisotropy in niosome solutions compared with that in pure aqueous solution indicates that HAN is located inside the motionally restricted bilayer region of niosome. The fluorescence quenching experiment further reveals the probable location of HAN in micelles and niosome. In TX100 micelles, the obtained lifetime values are 417 ps and 1.63 ns for the caged tautomers, whereas in the comparatively more rigid and confined environment provided by niosome those values are 444 ps and 2.5 ns. The rotational relaxation time constants for the caged tautomers in niosome are also found to be higher than those in micelles. The observed difference in binding ability of the different assemblies is due to the difference in the extent of water penetration and different extent of rigidity around the fluorophore.

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“…Till now, more and more systems containing 2 or more intramolecular or intermolecular hydrogen bonds have been focused, since it involves in more complex dynamic process. Particularly, the problem about whether only single proton transfer or double proton transfer process occurring in the excited state is still needed to be answered.…”

Section: Introductionmentioning

confidence: 99%

A theoretical assignment on excited‐state intramolecular proton transfer mechanism for quercetin

Yang

Zhao

et al. 2017

J of Physical Organic Chem

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In the present work, we investigate a new chromophore (ie, quercetin) (Simkovitch et al J Phys Chem B 119 [2015] 10244) about its complex excited-state intramolecular proton transfer (ESIPT) process based on density functional theory and timedependent density functional theory methods. On the basis of the calculation of electron density ρ(r) and Laplacian ∇ 2 ρ(r) at the bond critical point using atoms-in-molecule theory, the intramolecular hydrogen bonds (O 1 -H 2 ⋯O 5 and O 3 -H 4 ⋯O 5 ) have been supported to be formed in the S 0 state. Comparing the prime structural variations of quercetin involved in its 2 intramolecular hydrogen bonds, we find that these 2 hydrogen bonds should be strengthened in the S 1 state, which is a fundamental precondition for facilitating the ESIPT process. Concomitantly, infrared vibrational spectra analysis further verifies this viewpoint. In good agreement with previous experimental spectra results, we find that quercetin reveals 2 kinds of excited-state structures (quercetin* and quercetin-PT1*) in the S 1 state. Frontier molecular orbitals depict the nature of electronically excited state and support the ESIPT reaction. Our scanned potential energy curves according to variational O 1 -H 2 and O 3 -H 4 coordinates demonstrate that the proton transfer process should be more likely to occur in the S 1 state via hydrogen bond wire O 1 -H 2 ⋯O 5 rather than O 3 -H 4 ⋯O 5 because of the lower potential energy barrier 2.3 kcal/mol. Our present work explains previous experimental result and makes up the deficiency of mechanism in previous experiment. In the end, we make a reasonable assignment for ESIPT process of quercetin.

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Proton Phototransfers in Doubly Hydrogen Bonded Dimers: The Photophysics of 6,7,8,9-Tetrahydro-5H-pyrido[2,3-b]indole Dimers

Cited by 6 publications

References 34 publications

Photoinduced Proton and Charge Transfer in 2-(2′-Hydroxyphenyl)imidazo[4,5-b]pyridine

Photoinduced Proton and Charge Transfer in 2-(2′-Hydroxyphenyl)imidazo[4,5-b]pyridine

Photophysics and Photodynamics of 1′-Hydroxy-2′-acetonaphthone (HAN) in Micelles and Nonionic Surfactants Forming Vesicles: A Comparative Study of Different Microenvironments of Surfactant Assemblies

A theoretical assignment on excited‐state intramolecular proton transfer mechanism for quercetin

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