Water-Assisted Proton Transfer in the Monomer of 7-Azaindole

Folmer, D. E.; Wisniewski, E. S.; Stairs, Jason R.; Castleman, A. W.

doi:10.1021/jp0014263

Cited by 64 publications

(54 citation statements)

References 21 publications

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“…Ultrafast pump-probe spectroscopic studies on the hydrated 7-azaindole monomer provided evidence that an excited-state proton transfer can occur by means of a water proton bridge. [33] In addition, an ultrafast time-resolved transient absorption and resonance Raman spectroscopy study revealed that varying the water concentration in the solvent system changes the reaction rate of deprotection and rearrangement steps of the reaction for para- www.chemeurj.org hydoxyphenacyl diethylphosphate (HPDP) and para-hydroxyphenacyl dipehnylphosphate (HPPP) in H 2 O/MeCN mixed solvents. [34] Givens and co-workers also have suggested that a water molecule chain can carry a proton from the acidic p-OH site to the leaving-group phosphate.…”

Section: Resultsmentioning

confidence: 99%

Water‐ and Acid‐Mediated Excited‐State Intramolecular Proton Transfer and Decarboxylation Reactions of Ketoprofen in Water‐Rich and Acidic Aqueous Solutions

Yeung

Guan

et al. 2011

Chemistry A European J

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We present an investigation of the decarboxylation reaction of ketoprofen (KP) induced by triplet excited-state intramolecular proton transfer in water-rich and acidic solutions. Nanosecond time-resolved resonance Raman spectroscopy results show that the decarboxylation reaction is facile in aqueous solutions with high water ratios (water/acetonitrile ≥50%) or acidic solutions with moderate and strong acid concentration. These experimental results are consistent with results from density functional theory calculations in which 1) the activation energy barriers for the triplet-state intramolecular proton transfer and associated decarboxylation process become lower when more water molecules (from one up to four molecules) are involved in the reaction system and 2) perchloric acid, sulfuric acid, and hydrochloric acid can shuttle a proton from the carboxyl to carbonyl group through an initial intramolecular proton transfer of the triplet excited state, which facilitates the cleavage of the C-C bond, thus leading to the decarboxylation reaction of triplet state KP. During the decarboxylation process, the water molecules and acid molecules may act as bridges to mediate intramolecular proton transfer for the triplet state KP when KP is irradiated by ultraviolet light in water-rich or acidic aqueous solutions and subsequently it generates a triplet-protonated carbanion biradical species. The faster generation of triplet-protonated carbanion biradical in acidic solutions than in water-rich solutions with a high water ratio is also supported by the lower activation energy barrier calculated for the acid-mediated reactions versus those of water-molecule-assisted reactions.

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Section: Resultsmentioning

confidence: 99%

Water‐ and Acid‐Mediated Excited‐State Intramolecular Proton Transfer and Decarboxylation Reactions of Ketoprofen in Water‐Rich and Acidic Aqueous Solutions

Yeung

Guan

et al. 2011

Chemistry A European J

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“…2 of Ref. 5, are recorded only up to 7 ps. Thus, it is possible that a much longer time component is contained in their transient.…”

Section: Excited State Lifetimesmentioning

confidence: 99%

“…They attribute this behavior to a stepwise proton transfer from the 1H to the 7H position in the n = 2 and 3 cluster, while a single exponential decay for the n = 4 cluster was believed to be the signature of a concerted proton transfer. 5 Yokoyama et al performed IR-UV double resonance spectroscopy on 7-azaindole-water clusters together with ab initio molecular orbital calculations. 6 From their results hydrogen bonded single ring structures for the 7-azaindole͑H 2 O͒ n cluster with n =1-3 was deduced in the electronic ground state.…”

Section: Rotationally Resolved Electronic Spectroscopy Of Water Clustmentioning

confidence: 99%

“…22 Folmer et al found a biexponential decay with time constants of 360 and 6 ps in the excited state of 7-azaindole͑H 2 O͒ 2 using pump-probe spectroscopy. 5 They suggested that the existence of two different time constants points to a stepwise proton transfer reaction in the excited state. Later, Hara et al showed that, in the fluorescence emission spectra of the 7-azaindole͑H 2 O͒ 1-3 clusters in a molecular beam, no visible fluorescence could be detected.…”

Section: Excited State Lifetimesmentioning

confidence: 99%

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Rotationally resolved electronic spectroscopy of water clusters of 7-azaindole

Kalkman²,

Meerts³

et al. 2008

The Journal of Chemical Physics

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Electronically excited states of water clusters of 7-azaindole: Structures, relative energies, and electronic nature of the excited states J. Chem. Phys. 128, 214310 (2008) The rotationally resolved electronic spectra of the electronic origin of the 7-azaindole-͑H 2 O͒ 1 and of the 7-azaindole-͑H 2 O͒ 2 clusters have been measured in a molecular beam. From the rotational constants the structures in the S 0 and S 1 electronic states were determined as cyclic with the pyrrolo NH and the pyridino N atoms being bridged by one and two water molecules, respectively. Excited state lifetimes of about 10 ns for both clusters have been found. In the spectrum of the 7-azaindole-͑H 2 O͒ 2 cluster a splitting of the rovibronic band is observed, which can be traced back to a large amplitude motion, involving the out-of-plane hydrogen atoms of the water chain. Both the changes of the rotational constants upon electronic excitation and the orientation of the transition dipole point to a solvent induced state reversal between the L a and the L b states upon microsolvation.

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“…58,59,[62][63][64]69 Phototautomerization has also been discovered in complexes of 7AI with alcohols and water. [70][71][72][73][74][75][76][77][78][79][80][81][82][83][84] We have been carrying out detailed studies of bifunctional chromophores based on indole, pyrrole, pyridine, and carbazole units, such as 2-(2′-pyridyl)indoles, 4,5,8,13,18,20,21,31 2-(2′-pyridyl)-pyrrole, 32,85 7-(pyridyl)indoles, 35 dipyrido[2,3-a:3′,2′-i]carbazole, 10,22,25 7,8,9,10-tetrahydro-11H-pyrido [2,3-a]carbazole, 18,22 or 1H-pyrrolo [3,2-h]quinoline. 19,21,22,27,31,86 These molecules, structurally similar to 7AI, differ in the number of bonds between the proton donor (the NH group) and the acceptor (pyridine...…”

Section: Introductionmentioning

confidence: 99%

Structure and Photophysics of 2-(2‘-Pyridyl)benzindoles: The Role of Intermolecular Hydrogen Bonds

et al. 2007

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The photophysical properties of two isomeric 2-(2′-pyridyl)benzindoles depend on the environment. Strong fluorescence is detected in nonpolar and polar aprotic solvents. In the presence of alcohols, the emission reveals an unusual behavior. Upon titration of n-hexane solutions with ethanol, the fluorescence intensity goes through a minimum and then increases with rising alcohol concentration. Transient absorption and timeresolved emission studies combined with ground-and excited-state geometry optimizations lead to the conclusion that two rotameric forms, syn and anti, coexist in alcohols, whereas in nonpolar and aprotic polar media, only the syn conformation is present. The latter can form cyclic complexes with alcohols, which are rapidly depopulated in the excited state. In the presence of excess alcohol, syn f anti rotamerization occurs in the ground state, promoted by the cooperative action of nonspecific and specific effects such as solvent polarity increase and the formation of hydrogen bonds to both donor and acceptor sites of the bifunctional compounds.

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Water-Assisted Proton Transfer in the Monomer of 7-Azaindole

Cited by 64 publications

References 21 publications

Water‐ and Acid‐Mediated Excited‐State Intramolecular Proton Transfer and Decarboxylation Reactions of Ketoprofen in Water‐Rich and Acidic Aqueous Solutions

Water‐ and Acid‐Mediated Excited‐State Intramolecular Proton Transfer and Decarboxylation Reactions of Ketoprofen in Water‐Rich and Acidic Aqueous Solutions

Rotationally resolved electronic spectroscopy of water clusters of 7-azaindole

Structure and Photophysics of 2-(2‘-Pyridyl)benzindoles: The Role of Intermolecular Hydrogen Bonds

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