Viscosity vs. temperature effects in excited-state double proton transfer. Comparison of 1-azacarbazole with 7-azaindole

Waluk, Jacek; Grabowska, Anna; Pakuła, B.; Sepioł, Jerzy

doi:10.1021/j150650a028

Cited by 47 publications

(43 citation statements)

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“…The analysis of the spectrophotometric titration data by using the classical HendersonHasselbach equation [23] (inside the pH range) and the Excess Acidity Function method [24] (outside the pH range) renders pK a values of 4.10±0.05 and 14.5±0.2 for the C→N and N→A prototropic equilibria, respectively. These pK a values, in good agreement with those previously reported by others authors and ourselves [13,21], are similar to those published for 7AI (4.5±0.1 and 12.1, respectively) [8]. On the other hand, these pK a s values indicate that while the pyridinic nitrogen atom of AC is the less basic of the four isomers of the carboline ring, the acidity of the pyrrolic proton is similar within the carboline family [21].…”

Section: Spectral Characterization Of the Prototropic Species Of Ac Isupporting

confidence: 92%

“…Thus, using the mean of the absorption and emission wavelengths to estimate the frequencies ν Nd 0 28,682 cm −1 , ν Np 027,979 cm −1 , ν C 025,575 cm −1 and ν A 0 24,266 cm −1 the ΔpKas values of −5.0, and+9.3 for C→N p , and N d →A equilibria, respectively, have been obtained. Using a similar approach, Waluk et al [13] calculated ΔpKa values of −7.5 and +10.8 for the C→N and N→A equilibria, respectively. However, since these authors did not consider the existence of two different neutral species, these data cannot be directly compared with our data.…”

Section: Spectral Characterization Of the Prototropic Species Of Ac Imentioning

confidence: 99%

“…α-carboline, or 1-azacarbazole, AC, Scheme 1, is another representative diaza-aromatic molecule that can experience an ESDPT process and phototautomerism. Because of its structural relation with 7AI, the photophysics of AC has received outstanding attention [10][11][12][13][14][15][16][17][18][19][20]. Thus, it has been reported that AC forms, similarly to 7AI, cyclic doubly hydrogen-bonded dimers and solute/solvent complexes in hydrocarbon and alcoholic solvents, respectively.…”

Section: Introductionmentioning

confidence: 99%

“…Upon photoexcitation, these species promote the AC phototautomerism undergoing an ESDPT process and emitting dual fluorescence. In bulk water, AC also shows the apparently anomalous photophysical behavior of 7AI [10,13,19]. Consequently, it has been presumed that AC also forms cyclic doubly hydrogen bonded monohydrates similar to those of 7AI.…”

Section: Introductionmentioning

confidence: 99%

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Spectral and Photophysical Properties of α-carboline (1-Azacarbazole) in Aqueous Solutions

et al. 2011

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The absorption and fluorescence spectra of α-carboline, 9H-pyrido[2,3-b]indole, AC, in organic aprotic solvents containing different water proportions and in acid/base aqueous solutions inside and outside the pH range have been examined. In the organic aprotic solvents, the addition of increasing concentrations of water sequentially quenches and shifts to the red the fluorescence spectra of AC. These spectral changes have been rationalized assuming the formation, at the lower water concentrations, of a discrete ground state non-cyclic weakly fluorescent AC hydrate emitting at 376 nm that, upon increasing the water concentrations, evolves to a higher order AC poly hydrate emitting at 397 nm. The changes of the AC absorption spectra in aqueous acid/basic solutions indicate the existence of three ground state prototropic species; the pyridinic protonated cation, C (pK(a) = 4.10 ± 0.05), the neutral, N (pK(a) = 14.5 ± 0.2), and the pyrrolic deprotonated anion, A. Conversely, the changes of the AC fluorescence spectra in these media indicate the existence of four excited state species emitting at 376 nm, 397 nm, 460 nm and 465 nm. Since the emissions at 376 nm and 397 nm satisfactorily match those of the hydrates observed in the organic-water mixtures, they were consistently assigned to two differently hydrated ground state N species. The remaining emissions at 460 nm and 465 nm have been assigned without ambiguity, on the basis of their excitation spectra, to the C and A species, respectively. The excited-state pK(a)s of the prototropic species of AC have been estimated by using the Förster-Weller cycle.

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Section: Spectral Characterization Of the Prototropic Species Of Ac Isupporting

confidence: 92%

Section: Spectral Characterization Of the Prototropic Species Of Ac Imentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Spectral and Photophysical Properties of α-carboline (1-Azacarbazole) in Aqueous Solutions

et al. 2011

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“…This dimer has also been claimed that it can be used as a prototype system to mimic the elementary reactions involved in the photomutagenesis in the DNA base pairs [1,6]. Because of its structural relation with 7-AI, 1-azacarbazole dimer, (1-AC) 2 , has also long been recognized as a model for the DNA base pairs and has attracted considerable interest as a model system to investigate the phototautomerism of 7-AI [7][8][9]. Figure 1 shows schematically the photo-tautomerization process of these dimers involving a double proton-transfer reaction, and the process has been thoroughly studied in solution with various laser spectroscopic techniques in order to understand whether this process can be of significance in mutagenesis [10][11][12][13][14].…”

Section: Introductionmentioning

confidence: 99%

Dynamics of proton transfer reactions of model base pairs in the ground and excited states: Revisited

Fuke

Ishikawa

2015

Chemical Physics Letters

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A review of the proton transfer reactions (PTR) of model base pairs such as the 7-azaindole and 1-azacarbazole dimers is presented, including some of the recent progress in the laser spectroscopy of these dimers. Advances in computational chemistry now allow to calculate reliable potential energy surfaces of the excited-state PTR, which is indispensable to understand the experimental results. The comprehensive results on the spectroscopy and reactivity of these dimers are outlined for fully explaining the excited state PTR of model base pairs on the basis of the current theoretical studies. Moreover, the recent studies on the PTR in the ground state relating to a back proton translocation of tautomeric dimer of 7-azaindole are presented. Finally, the outlook on the study of the PTR of model base pairs is addressed to further explore the reaction dynamics of these benchmark systems.

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Excited‐State Double Proton Transfer in Model Base Pairs: The Stepwise Reaction on the Heterodimer of 7‐Azaindole Analogues

Hsieh

Lai

et al. 2008

ChemPhysChem

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A four fused-ring system 11-propyl-6H-indolo[2,3-b]quinoline (6 HIQ) is strategically designed and synthesized; it possesses a central moiety of 7-azaindole (7AI) and undergoes excited-state double proton transfer (ESDPT). Despite a barrierless type of ESDPT in the 6 HIQ dimer, femtosecond dynamics and a kinetic isotope effect provide indications for a stepwise ESDPT process in the 6 HIQ/7AI heterodimer, in which 6 HIQ (deuterated 6 HIQ) delivers the pyrrolyl proton (deuteron) to 7AI (deuterated 7AI) in less than 150 fs, forming an intermediate with a charge-transfer-like ion pair, followed by the transfer of a pyrrolyl proton (deuteron) from cation-like 7AI (deuterated 7AI) to the pyridinyl nitrogen of the anion-like 6 HIQ (deuterated 6 HIQ) in approximately 1.5+/-0.3 ps (3.5+/-0.3 ps). The barrier of second proton transfer is estimated to be 2.86 kcal mol(-1) for the 6 HIQ/7AI heterodimer.

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Viscosity vs. temperature effects in excited-state double proton transfer. Comparison of 1-azacarbazole with 7-azaindole

Cited by 47 publications

References 3 publications

Spectral and Photophysical Properties of α-carboline (1-Azacarbazole) in Aqueous Solutions

Spectral and Photophysical Properties of α-carboline (1-Azacarbazole) in Aqueous Solutions

Dynamics of proton transfer reactions of model base pairs in the ground and excited states: Revisited

Excited‐State Double Proton Transfer in Model Base Pairs: The Stepwise Reaction on the Heterodimer of 7‐Azaindole Analogues

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