Spectroscopic Study of Hydrogen Bonded7‐Azaindole Clusters

Nakajima, Atsushi; Ono, Fumiko; Kihara, Yuya; Ogawa, Akiko; Matsubara, Kayo; Ishikawa, Kiyoshi; Baba, Masaaki; Kaya, Kunimitsu

doi:10.1155/1995/63470

Cited by 25 publications

(20 citation statements)

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“…discussed in terms of the use of mass spectrometry and photoelectron spectroscopy. Figure 1 shows a TOF mass spectrum of (7-AzI) − n cluster anions produced with the pulsed discharge nozzle, which was almost the same as the mass spectrum obtained by the injection of electrons into the 7-AzI beam [24]. Analysis of the mass spectrum shows that no hydrogen atoms are lost, even with this discharge nozzle.…”

Section: Resultsmentioning

confidence: 65%

“…The details of the experimental setup have been provided elsewhere [24]. Briefly, the apparatus consists of a pulsed cluster anion source, a time-of-flight (TOF) mass spectrometer, and a magnetic bottle TOF spectrometer.…”

Section: Methodsmentioning

confidence: 99%

“…Furthermore, the geometric structure of 7-AzI clusters intrigues us, because it is capable of self-associating through hydrogen bonds [23,24]. Since a 7-AzI cluster has both donor and acceptor sites for hydrogen bonding, the geometric arrangements can lead to the formation of cyclic structures and/or open-chain structures.…”

Section: Introductionmentioning

confidence: 99%

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Photoelectron spectroscopy of 7-azaindole–water cluster anions

Nakajima

Hasumi

Kaya

1999

The European Physical Journal D

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The 7-azaindole (7-AzI) cluster anions and their H 2 O adducts were generated by electron attachment to the 7-AzI/7-AzI-H 2 O clusters, and their electronic properties studied with mass spectrometry and photoelectron spectroscopy. In the mass spectra of the 7-AzI cluster anions, (7-AzI) − n , monomer anions were missing due to negative electron affinity (EA), while clusters (n ≥ 2) have positive EA, and those having even n were more abundant than those at odd n. EA increased with cluster size from 0.88 eV at n = 2, and an even-odd alternation in the EA was seen. The even-odd alternation showed that the 7-AzI dimer acts as a unit for cluster formation. In the photoelectron spectrum of (7-AzI) − 2 at 266 nm, the second peak was observed 2.4 eV above the first peak; this is attributed to the triplet state of the neutral (7-AzI) 2 . Depending on the detachment energy, a movable peak, with the detachment of 420-300 nm (2.9-4.1 eV), was additionally observed between the first and the second peaks; this was thought to be caused by a delayed photoemission via an electronic excited state of the (7-AzI) − 2 anion.

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Section: Resultsmentioning

confidence: 65%

Section: Methodsmentioning

confidence: 99%

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Photoelectron spectroscopy of 7-azaindole–water cluster anions

Nakajima

Hasumi

Kaya

1999

The European Physical Journal D

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“…Even though the structure of the reactive dimer is well known and documented, currently we can only speculate about the structure of the nonreactive dimer despite the information presented in this study. 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).…”

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%

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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