High-Resolution Laser-Induced Fluorescence Spectra of 7-Azaindole−Water Complexes and 7-Azaindole Dimer

Nakajima, Atsushi; Hirano, Masahiro; Hasumi, R.; Kaya, Kunimitsu; Watanabe, Hidekazu; Carter, C. C.; Williamson, James M.; Miller, Terry A.

doi:10.1021/jp9614411

Cited by 108 publications

(105 citation statements)

References 31 publications

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“…The calculations for the adiabatic excitations predict a red shift in the excitation energy upon complexation with one water, in agreement with experiment, although the calculated MCQDPT2 red shift of 1.3 kcal/mol is somewhat smaller than the experimental value of 3.7 kcal/mol. 5,12 The tautomer (which is more stable in the excited state) is very slightly destabilized by the water molecule, so that energy difference between isomers becomes 18 kcal/mol, compared with 20 kcal/mol in the isolated structures as discussed above. The transition state for the tautomerization reaction (found at the MCSCF level) is shown in Figure 6.…”

Section: Resultsmentioning

confidence: 95%

The Ground and Excited State Hydrogen Transfer Potential Energy Surface in 7-Azaindole

Chaban

Gordon

1998

J. Phys. Chem. A

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Multireference wave functions, augmented by second-order perturbation theory, are used to examine the hydrogen transfer process in the ground and first excited states of 7-azaindole and in the 1:1 7-azaindole:water complex. The presence of one water molecule dramatically reduces the barrier to proton transfer in both electronic states. In the excited state the order of the two tautomers is reversed, and the barrier for the hydrogen transfer from the (now higher energy) normal structure to the tautomer in the presence of one water is estimated to be ≤6 kcal/mol. Disciplines Chemistry CommentsReprinted (adapted) ReceiVed: September 18, 1998; In Final Form: NoVember 4, 1998 Multireference wave functions, augmented by second-order perturbation theory, are used to examine the hydrogen transfer process in the ground and first excited states of 7-azaindole and in the 1:1 7-azaindole: water complex. The presence of one water molecule dramatically reduces the barrier to proton transfer in both electronic states. In the excited state the order of the two tautomers is reversed, and the barrier for the hydrogen transfer from the (now higher energy) normal structure to the tautomer in the presence of one water is estimated to be e6 kcal/mol.

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Section: Resultsmentioning

confidence: 95%

The Ground and Excited State Hydrogen Transfer Potential Energy Surface in 7-Azaindole

Chaban

Gordon

1998

J. Phys. Chem. A

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“…Kaya suggested three possible structures for the nonreactive dimer: T shaped, single bonded, and out of plane (8). High-resolution laser-induced fluorescence (LIF) studies in conjunction with simulated LIF structures for each species led Kaya and coworkers to conclude that the T-shaped structure is favored (9). However, in considering our findings that a water molecule actually enhances the reaction of the nonreactive dimer originally discussed by Kaya, we believe that Lopez-Martens et al's suggestion (17) that a biparallel dimer with out-of-plane hydrogen atoms is a reasonable possibility for the structure of the nonreactive dimer.…”

Section: Discussionmentioning

confidence: 99%

“…This ESDPT was first observed in solution by Kasha and coworkers (5). Later, Kaya and coworkers performed extensive supersonic jet spectroscopic studies on the 7-Aza monomer, dimer, and solvated forms of these species (6)(7)(8)(9). The first direct determination of the rates of the double-proton transfer was made in the gas phase by Zewail and coworkers (10), who provided definitive evidence for a stepwise rather than a concerted process.…”

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confidence: 89%

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Femtosecond cluster studies of the solvated 7-azaindole excited state double-proton transfer

Folmer

Wisniewski

Hurley

et al. 1999

Proc. Natl. Acad. Sci. U.S.A.

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Presented here are femtosecond pump-probe studies on the watersolvated 7-azaindole dimer, a model DNA base pair. In particular, studies are presented that further elucidate the nature of the reactive and nonreactive dimers and also provide new insights establishing that the excited state double-proton transfer in the dimer occurs in a stepwise rather than a concerted manner. A major question addressed is whether the incorporation of a water molecule with the dimer results in the formation of species that are unable to undergo excited state double-proton transfer, as suggested by a recent study reported in the literature [Nakajima, A., Hirano, M., Hasumi, R., Kaya, K., Watanabe, H., Carter, C. C., Williamson, J. M. & Miller, T. (1997) J. Phys. Chem. 101, 392-398]. In contrast to this earlier work, our present findings reveal that both reactive and nonreactive dimers can coexist in the molecular beam under the same experimental conditions and definitively show that the clustering of water does not induce the formation of the nonreactive dimer. Rather, when present with a species already determined to be a nonreactive dimer, the addition of water can actually facilitate the occurrence of the proton transfer reaction. Furthermore, on attaining a critical hydration number, the data for the nonreactive dimer suggest a solvation-induced conformational structure change leading to proton transfer on the photoexcited half of the 7-azaindole dimer. C luster science studies have long been utilized to yield unique perspectives of microscopic properties related to the bulk condensed phase (1). This approach involves the investigation of a broad spectrum of clusters ranging from isolated species to the study of fully solvated species, thus illustrating the progression from the gas phase to the condensed phase. In reference to our specific experiments as an example, we have been able to study the excited state double-proton transfer (ESDPT) of the 7-azaindole (7-Aza) dimer under conditions ranging from an isolated dimer to a state of solvation where the hydrogen-bonded dimer is clustered with as many as nine water molecules. As the number of water molecules on the nonreactive dimer increases, we begin to see evidence that the dimer molecule is behaving more as it would in a fully solvated condensed-phase environment. In support of these findings, it has been reported that clusters with as little as six waters begin to show liquid-like properties (2-4).The model DNA base pair 7-Aza has proven to be an interesting and enlightening species for study in both the gas and condensed phases. Of utmost interest is the double-proton transfer that the 7-Aza dimer undergoes on excitation to the S 1 state. This ESDPT was first observed in solution by Kasha and coworkers (5). Later, Kaya and coworkers performed extensive supersonic jet spectroscopic studies on the 7-Aza monomer, dimer, and solvated forms of these species (6-9). The first direct determination of the rates of the double-proton transfer was made in the gas phase by Zewail and c...

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“…Nakajima et al 4 investigated the geometric structures of 7-azaindole͑H 2 O͒ 1-3 and of the 7-azaindole dimer using laser-induced fluorescence spectroscopy with high resolution ͑ϳ0.01 cm −1 , equivalent to 300 MHz͒. They deduced a planar ring structure of 7-azaindole͑H 2 O͒ 1 from the rotational analysis of the spectrum and from ab initio calculations.…”

Section: Rotationally Resolved Electronic Spectroscopy Of Water Clustmentioning

confidence: 99%

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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High-Resolution Laser-Induced Fluorescence Spectra of 7-Azaindole−Water Complexes and 7-Azaindole Dimer

Cited by 108 publications

References 31 publications

The Ground and Excited State Hydrogen Transfer Potential Energy Surface in 7-Azaindole

The Ground and Excited State Hydrogen Transfer Potential Energy Surface in 7-Azaindole

Femtosecond cluster studies of the solvated 7-azaindole excited state double-proton transfer

Rotationally resolved electronic spectroscopy of water clusters of 7-azaindole

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