Study of 7-azaindole in its first four singlet states

Catalán, Javier; Paz, J. L. G. De

doi:10.1063/1.1940607

Cited by 16 publications

(12 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…42 Considering that the ESDPT in the 7AIÀCH 3 OH complex was highly exothermic to give an early TS based on the Hammond's postulate and that different computational levels were used, the q 1 values of transferring protons in two complexes agreed well with each other. These results suggest that the acidity of the pyrrolic proton in 7AI, which becomes larger upon excitation, 44 might be similar to that of acetic acid.…”

Section: Resultsmentioning

confidence: 77%

Theoretical Studies for Excited-State Tautomerization in the 7-Azaindole–(CH₃OH)_n (n = 1 and 2) Complexes in the Gas Phase

Fang

Kim

2011

J. Phys. Chem. A

View full text Add to dashboard Cite

The excited-state tautomerization of 7-azaindole (7AI) complexes bonded with either one or two methanol molecule(s) was studied by systematic quantum mechanical calculations in the gas phases. Electronic structures and energies for the reactant, transition state (TS), and product were computed at the complete active space self-consistent field (CASSCF) levels with the second-order multireference perturbation theory (MRPT2) to consider the dynamic electron correlation. The time-dependent density functional theory (TDDFT) was also used for comparison. The excited-state double proton transfer (ESDPT) in 7AI-CH(3)OH occurs in a concerted but asynchronous mechanism. Similarly, such paths are also found in the two transition states during the excited-state triple proton transfer (ESTPT) of the 7AI-(CH(3)OH)(2) complex. In the first TS, the pyrrole ring proton first migrated to methanol, while in the second the methanol proton moved first to the pyridine ring. The CASSCF level with the MRPT2 correction showed that the former path was much preferable to the latter, and the ESDPT is much slower than the ESTPT. Additionally, the vibrational-mode enhanced tautomerization in the 7AI-(CH(3)OH)(2) complex was also studied. We found that the excitation of the low-frequency mode shortens the reaction path to increase the tautomerization rate. Overall, most TDDFT methods used in this study predicted different TS structures and barriers from the CASSCF methods with MRPT2 corrections.

show abstract

Section: Resultsmentioning

confidence: 77%

Theoretical Studies for Excited-State Tautomerization in the 7-Azaindole–(CH₃OH)_n (n = 1 and 2) Complexes in the Gas Phase

Fang

Kim

2011

J. Phys. Chem. A

View full text Add to dashboard Cite

show abstract

“…48 In 7-azaindole, 1 L a is found to be the fluorescent state even in the vapor phase according to CASSCF [49][50][51] and TDDFT studies. 52 It has been noted that, since in polycyclic aromatic molecules the 1 L b state is characterized by the essential multiconfigurational character, its energy is often overestimated by such single-referenced methods as TDDFT by 0.2-0.4 eV. 53 As a result, TDDFT calculations predict correctly the energy of the 1 1 A′ f 1 L a excitation, whereas they tend to overestimate the energy of the 1 L b state.…”

Section: Pq Monomermentioning

confidence: 97%

Excited-State Proton Transfer through Water Bridges and Structure of Hydrogen-Bonded Complexes in 1H-Pyrrolo[3,2-h]quinoline: Adiabatic Time-Dependent Density Functional Theory Study

Kyrychenko

Waluk

2006

J. Phys. Chem. A

View full text Add to dashboard Cite

Proton transfer reaction is studied for 1H-pyrrolo[3,2-h]quinoline-water complexes (PQ-(H(2)O)(n), n = 0-2) in the ground and the lowest excited singlet states at the density functional theory (DFT) level. Cyclic hydrogen-bonded complexes are considered, in which water molecules form a bridge connecting the proton donor (pyrrole NH group) and acceptor (quinoline nitrogen) atoms. To understand the effect of the structure and length of water bridges on the excited-state tautomerization in PQ, the potential energy profile of the lowest excited singlet state is calculated adiabatically by the time-dependent DFT (TDDFT) method. The S(0) --> S(1) excitation of PQ is accompanied by significant intramolecular transfer of electron density from the pyrrole ring to the quinoline fragment, so that the acidity of the N-H group and the basicity of the nitrogen atom of the quinoline moiety are increased. These excited-state acid-base changes introduce a driving force for the proton transfer reaction. The adiabatic TDDFT calculations demonstrate, however, that the phototautomerization requires a large activation energy in the isolated PQ molecule due to a high energy barrier separating the normal form and the tautomer. In the 1:1 cyclic PQ-H(2)O complex, the energy barrier is dramatically reduced, so that upon excitation of this complex the tautomerization can occur rapidly in one step as concerted asynchronous movements of the two protons assisted by the water molecule. In the PQ-(H(2)O)(2) solvate two water molecules form a cyclic bridge with sterically strained and unfavorable hydrogen bonds. As a result, some extra activation energy is needed for initiating the proton dislocation along the longer hydrogen-bond network. The full tautomerization in this complex is still possible; however, the cooperative proton transfer is found to be highly asynchronous. Large relaxation and reorganization of the hydrogen-bonded water bridge in PQ-(H(2)O)(2) are required during the proton translocation from the pyrrole NH group to the quinoline nitrogen; this may block the complete tautomerization in this type of solvate.

show abstract

“…1) which has 7-azaindole moiety instead. It has been shown that indole and 7-azaindole have different physical and photophysical properties and the difference is due to the presence of electron withdrawing pyridyl nitrogen in 7-azaindole [12][13][14]. The presence of the potent Hbond acceptor pyridyl nitrogen in 7-azaserotonin makes it biologically interesting, like 7-azaindole and its analogs [15].…”

Section: Introductionmentioning

confidence: 97%

Effect of pyridyl nitrogen on the conformational landscape of 7-azaserotonin: A computational study

Biswal¹,

Wategaonkar²

2009

Journal of Molecular Structure: THEOCHEM

View full text Add to dashboard Cite

Study of 7-azaindole in its first four singlet states

Cited by 16 publications

References 37 publications

Theoretical Studies for Excited-State Tautomerization in the 7-Azaindole–(CH₃OH)_n (n = 1 and 2) Complexes in the Gas Phase

Theoretical Studies for Excited-State Tautomerization in the 7-Azaindole–(CH₃OH)_n (n = 1 and 2) Complexes in the Gas Phase

Excited-State Proton Transfer through Water Bridges and Structure of Hydrogen-Bonded Complexes in 1H-Pyrrolo[3,2-h]quinoline: Adiabatic Time-Dependent Density Functional Theory Study

Effect of pyridyl nitrogen on the conformational landscape of 7-azaserotonin: A computational study

Contact Info

Product

Resources

About

Study of 7-azaindole in its first four singlet states

Cited by 16 publications

References 37 publications

Theoretical Studies for Excited-State Tautomerization in the 7-Azaindole–(CH3OH)n (n = 1 and 2) Complexes in the Gas Phase

Theoretical Studies for Excited-State Tautomerization in the 7-Azaindole–(CH3OH)n (n = 1 and 2) Complexes in the Gas Phase

Excited-State Proton Transfer through Water Bridges and Structure of Hydrogen-Bonded Complexes in 1H-Pyrrolo[3,2-h]quinoline: Adiabatic Time-Dependent Density Functional Theory Study

Effect of pyridyl nitrogen on the conformational landscape of 7-azaserotonin: A computational study

Contact Info

Product

Resources

About

Theoretical Studies for Excited-State Tautomerization in the 7-Azaindole–(CH₃OH)_n (n = 1 and 2) Complexes in the Gas Phase

Theoretical Studies for Excited-State Tautomerization in the 7-Azaindole–(CH₃OH)_n (n = 1 and 2) Complexes in the Gas Phase