Molecular and supramolecular proton-transfer processes in 2(2′-hydroxyphenyl)-3H-imidazo[4,5-b]pyridine and its derivatives

Salman, Husein; Meltzman, Shai; Speiser, Shammai; Eichen, Yoav

doi:10.1016/s0022-2313(02)00513-6

Cited by 4 publications

(7 citation statements)

References 9 publications

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“…Scheme 2 depicts the proposed acid-base processes for 10 and 17. All the above phenomena are similar to other proton transfer driven systems [21].…”

Section: Solution Spectroscopysupporting

confidence: 85%

Crystal structures and solution spectroscopy of lophine derivatives

Fridman¹,

Kaftory²,

Eichen³

et al. 2009

Journal of Molecular Structure

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“…Scheme 2 depicts the proposed acid-base processes for 10 and 17. All the above phenomena are similar to other proton transfer driven systems [21].…”

Section: Solution Spectroscopysupporting

confidence: 85%

Crystal structures and solution spectroscopy of lophine derivatives

Fridman¹,

Kaftory²,

Eichen³

et al. 2009

Journal of Molecular Structure

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“…Salman et al report that diluted solutions of 1 in acetonitrile do not obey Beer's law due to the establishment of a dimerization equilibrium. 60 According to these authors, the equilibrium is completely shifted to the dimer in tetrahydrofuran, pentane, and ethanol, while in acetonitrile at low concentrations some dissociation of the dimer takes place.…”

Section: Resultsmentioning

confidence: 99%

“…48,58,59 Salman et al studied the influence of sample concentration on the spectra of 1 in different solvents. 60 Dual fluorescence was observed for 1 in different solvents. Krishnamoorthy, Dogra et al interpreted the strongly Stokes-shifted fluorescence band of 1 as being due to the emission of the tautomer obtained by the unimolecular ESIPT process from the hydroxyl group to the benzimidazole N, whereas the normal-Stokes-shifted band was assigned to the emission of conformers lacking the intramolecular hydrogen bond and therefore unable to undergo ESIPT.…”

Section: Introductionmentioning

confidence: 97%

“…The double fluorescence of 1 would be due, according to these authors, to the simultaneous emission of the proton-transferred H-bonded dimers and of the ESIPT tautomer. 60 The study described here was aimed specifically at establishing (a) the nature of the species present in the ground state in solutions of 1 in several solvents at different acidities, (b) the characteristics of the photoinduced processes undergone by these species, and (c) the influence of molecular structure on the fluorescence features of the excited species.…”

Section: Introductionmentioning

confidence: 99%

“…Concentration and solvent influence on the absorption spectra: no observable dimerization in the working concentration range. Salman et al report that diluted solutions of 1 in acetonitrile do not obey Beer's law due to the establishment of a dimerization equilibrium 60. …”

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confidence: 99%

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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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Microwave‐Assisted C‐2 Direct Alkenylation of Imidazo[4,5‐b]pyridines: Access to Fluorescent Purine Isosteres with Remarkably Large Stokes Shifts

2016

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We describe herein the first C‐2 direct alkenylation of the valuable 3H‐imidazo[4,5‐b]pyridine promoted by microwave‐assisted Pd/Cu co‐catalysis. The reaction is rapid and compatible with a wide range of functional groups either on the imidazo[4,5‐b]pyridine ring or on the styryl bromides thereby leading to the isolation of 23 compounds with moderate to good yields. The relevance of this method is demonstrated by its application to the synthesis of new cross‐conjuguated push–pull 2‐vinyl‐ and 2‐alkynylimidazo[4,5‐b]pyridines characterized by satisfactory fluorescence quantum yields and remarkable solvatofluorochromic properties.

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Molecular and supramolecular proton-transfer processes in 2(2′-hydroxyphenyl)-3H-imidazo[4,5-b]pyridine and its derivatives

Cited by 4 publications

References 9 publications

Crystal structures and solution spectroscopy of lophine derivatives

Crystal structures and solution spectroscopy of lophine derivatives

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

Microwave‐Assisted C‐2 Direct Alkenylation of Imidazo[4,5‐b]pyridines: Access to Fluorescent Purine Isosteres with Remarkably Large Stokes Shifts

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Molecular and supramolecular proton-transfer processes in 2(2′-hydroxyphenyl)-3H-imidazo[4,5-b]pyridine and its derivatives

Cited by 4 publications

References 9 publications

Crystal structures and solution spectroscopy of lophine derivatives

Crystal structures and solution spectroscopy of lophine derivatives

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

Microwave‐Assisted C‐2 Direct Alk­enylation of Imidazo[4,5‐b]pyr­idines: Access to Fluorescent Purine Isosteres with Remarkably Large Stokes Shifts

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Microwave‐Assisted C‐2 Direct Alkenylation of Imidazo[4,5‐b]pyridines: Access to Fluorescent Purine Isosteres with Remarkably Large Stokes Shifts