Red edge excitation study of cooperative double proton transfer in 7-azaindole

Waluk, Jacek; Bulska, Hanna; Pakuła, B.; Sepioł, Jerzy

doi:10.1016/0022-2313(81)90030-2

Cited by 30 publications

(22 citation statements)

References 3 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…7-Azaindole and its dimer have produced considerable insight into the type of ESDPT implicated in DNA mutagenesis. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] In a series of investigations the complexation of the 2-(2 0 -pyridyl)indole system with alcohols has been studied. [20][21][22][23][24][25][26] This work primarily used spectroscopic probes to study the nature of solvent-solute complexation and to investigate ESDPT enabled by a hydrogen bonded alcohol bridge between the donor and acceptor nitrogens on the indole and pyridyl rings, respectively.…”

Section: Introductionmentioning

confidence: 99%

2-(2′-Pyridyl)pyrroles: Part I. Structure and energetics of pyridylpyrroles, their dimers, complexes and excited states

Schmidtke

MacManus-Spencer

Klappa

et al. 2004

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

Section: Introductionmentioning

confidence: 99%

2-(2′-Pyridyl)pyrroles: Part I. Structure and energetics of pyridylpyrroles, their dimers, complexes and excited states

Schmidtke

MacManus-Spencer

Klappa

et al. 2004

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

“…This dimer certainly seems to be the main stable one observed in equilibrium conditions at 298 K in solution studies, and the essential one by which to observe biprotonic transfer dimer f luorescence. Previously, a ''nonreactive'' (non-proton-transfer) dimer (15,16) and larger oligomeric forms of 7AI have been suggested (31)(32)(33). Fuke and Kaya (16) demonstrated that the relative amount of reactive and nonreactive dimers depends on the stagnation pressure of the carrier gas.…”

Section: Dimerization Modes Of 7ai In Adiabatic Nozzle Supercooled Momentioning

confidence: 99%

The concerted mechanism of photo-induced biprotonic transfer in 7-azaindole dimers: Structure, quantum-theoretical analysis, and simultaneity principles

Catalán

Pérez

Valle

et al. 2002

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

View full text Add to dashboard Cite

Six stable dimer models for 7-azaindole (including the classic C2h doubly hydrogen-bonded, coplanar, centrosymmetric dimer) are considered to be observable in adiabatic nozzle jet molecular beams. They are analyzed by hybrid density functional theory (DFT), the MP2 ab initio method for the ground electronic state, and the single-excitation configuration interaction (CIS) (over frozen ground state optimized geometries obtained from DFT) excited state calculations, for global potential minima and proton-transfer potential energy curves. Three simultaneity principles are stated: (i) intermolecular coherent excitation molecular exciton simultaneity, (ii) intramolecular acid-base change simultaneity at the pyrrolo-N-H and aza-N proton-donor, proton-acceptor sites, and (iii) intermolecular simultaneity of catalytic proton-donor, proton-acceptor action. It is suggested that the formation of the classic C2h dimer of 7-azaindole, which is considered exclusively by previous researchers, can be formed from at least one of the several card-pack hydrogen-bonded dimers in a secondary slower step approaching a microsecond scale, instead of the picosecond events at the supersonic nozzle. It is proposed that the complexity of dimerization modes is the basis of the postexcitation, postionization diverse kinetic isotope results.T he photoinduced biprotonic transfer in the classic 7-azaindole (7AI) hydrogen-bonded C 2h dimer (refs. 1 and 2 and references therein) seemingly has revealed contrasting mechanisms according to the experimental techniques applied. Electronic spectroscopic observations and quantum theoretical calculations require a concerted (3) one-step simultaneous intermolecular transfer of the two protons involved in the hydrogen bonding of the 7AI base pair. In contrast, femtosecond laser-pulsed photo-excitation followed by femtosecond laserpulsed ionization and then time-of-flight (TOF) mass spectrometry (4-6), or with giant laser pulse-induced coulomb explosion (7, 8) followed by TOF mass spectrometry of the resultant ions (and molecular fragments), has suggested to these researchers a two-step neutral H-atom transfer, based on kinetic analysis of the ion appearance and isotopic effects. We shall return to the question of neutral H-atom transfer vs. H ϩ (proton) transfer at the end of the companion paper (9).In the first part of this paper, we give an outline summary of the spectroscopic demands on simultaneity of the biprotonic transfer for the concerted transfer mechanism, and then in the second part we present an analysis of the structures and protontransfer potential functions and the energies of formation for the variety of 7AI stable dimers that could form at supersonic velocities in the adiabatic-nozzle supercooled molecular beam. This presentation is suggested as a pathway to resolving the conflict between the spectroscopic and the kinetic results. Background of 7AI Dimer Biprotonic TransferFor photo-induced biprotonic transfer we emphasize three strict requirements of simultaneity of action that must exist.

show abstract

“…In 1980, Bulska and Chodkowska [2] examined the ESR and luminescence spectra of concentrated solutions (10 Ϫ3 to 10 Ϫ2 M) of 7AI in 3MP at 77 K and found them to exhibit phosphorescence with the 0 -0 component at 426 nm; they concluded that "Our measurements show that, at low temperatures, the tautomeric fluorescence is overlapped by the isoenergetic monomeric phosphorescence" (i.e., they assigned the phosphorescence to the monomer form, T 1 (M)). In 1981, Waluk et al [3] discussed this assignment and noted that it was highly unlikely for the observed phosphorescence of a 10 Ϫ2 M solution of 7AI in 3MP at 77 K to belong to monomeric 7AI [T 1 (M)], since only the dimeric form stable in the ground electronic state [S 0 n (D)] was excited and concluded that the phosphorescing triplets [T 1 n (D)] must be generated via tautomeric [S 1 t (D)] singlets and that the phosphorescence must involve back-proton transfer according to:…”

mentioning

confidence: 98%

On the molecular structure that produces the phosphorescence of 7‐azaindole

Catalán

2004

Int J of Quantum Chemistry

View full text Add to dashboard Cite

ABSTRACT:The structured phosphorescence with a 0 -0 component at ϳ430 nm exhibited by 7-azaindole is not due to its monomer, its normal or tautomeric C 2h dimer, or its oligomeric forms consisting of five monomers, but rather to a molecular structure resulting from the interaction of the C 2h dimer with a polar molecule (7-azaindole itself, another solute or the solvent). Such an interaction breaks the C 2h symmetry of 7-azaindole dimer, thereby facilitating the localization of the electronic excitation on one of the dimer molecules and resulting in the presence of dimers of C 1 symmetry. Based on the results, the structure that produces this phosphorescence is a normal dimer exhibiting a double hydrogen bond but no symmetry constraint. Surprisingly, its first triplet state, T 1 n (D C1 ), is ϳ20 kcal/mol below the first triplet state for the system of C 2h symmetry.

show abstract

Red edge excitation study of cooperative double proton transfer in 7-azaindole

Cited by 30 publications

References 3 publications

2-(2′-Pyridyl)pyrroles: Part I. Structure and energetics of pyridylpyrroles, their dimers, complexes and excited states

2-(2′-Pyridyl)pyrroles: Part I. Structure and energetics of pyridylpyrroles, their dimers, complexes and excited states

The concerted mechanism of photo-induced biprotonic transfer in 7-azaindole dimers: Structure, quantum-theoretical analysis, and simultaneity principles

On the molecular structure that produces the phosphorescence of 7‐azaindole

Contact Info

Product

Resources

About