Photoelectron Spectroscopy of the 6-Azauracil Anion

Chen, Jing; Buonaugurio, Angela; Dolgounitcheva, O.; Zakrzewski, V. G.; Bowen, Kit H.; Ortiz, J. V.

doi:10.1021/jp303964j

Cited by 4 publications

(11 citation statements)

References 54 publications

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“…The VEDE of the most stable, canonical VB anion of 5-azauracil is predicted to exceed 1 eV and is comparable to its counterpart obtained experimentally and theoretically for 6-azauracil. 23 The closest anionic structure, 13, a very rare tautomer, has a VEDE above 2 eV. Thus, these two structures might be represented in photoelectron spectra of anionic 5-azauracil.…”

Section: ■ Resultsmentioning

confidence: 99%

“…The valence-bound, canonical anion of 5-azauracil is expected to be observed under experimental conditions comparable with those reported for 6-azauracil or thiouracils. 23 A wide band is expected in a photoelectron spectrum of the VB anion, for its VEDE is 1.1 eV. A very rare, imino−oxo, VB tautomer also may be observed in such experiments and will have a peak near 2.0 eV.…”

Section: ■ Conclusionmentioning

confidence: 93%

“…The VB anion of 6-azauracil has been observed experimentally and studied theoretically. 23 This anion also was stable adiabatically (and therefore vertically) and gave rise to a broad band with a maximum at 1.2 eV. This peak was assigned to electron detachment from a canonical structure of 6-azauracil.…”

Section: ■ Introductionmentioning

confidence: 96%

“…A typical DB anion is identified by a sharp, narrow peak with an electron binding energy close to zero, 30 whereas a typical VB anion is characterized by a broad, structured peak with a maximum usually at about 1−1.5 eV. 23 In principle, a molecule could form anions of both types. The canonical form of uracil was found to produce a weakly bound DB anion 30−32 with a vertical electron detachment energy (VEDE) measured at 0.086 eV.…”

Section: ■ Introductionmentioning

confidence: 99%

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Valence-Bound and Diffuse-Bound Anions of 5-Azauracil

et al. 2014

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Structures, isomerization energies, and electron binding energies of 5-azauracil and its anions have been calculated ab initio with perturbative, coupled-cluster, and electron-propagator methods. Tautomeric structures, including those produced by proton transfer to a CH group, have been considered. Dyson orbitals and pole strengths from electron-propagator calculations validated a simple, molecular-orbital picture of anion formation. In one case, an electron may enter a delocalized π orbital, yielding a valence-bound (VB) anion with a puckered ring structure. The corresponding electron affinity is 0.27 eV; the vertical electron detachment energy (VEDE) of this anion 1.05 eV. An electron also may enter a molecular orbital that lies outside the nuclear framework, resulting in a diffuse-bound (DB) anion. In the latter case, the electron affinity is 0.06 eV and the VEDE of the DB anion is 0.09 eV. Another VB isomer that is only 0.02 eV more stable than the neutral molecule has a VEDE of 2.0 eV.

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Section: ■ Resultsmentioning

confidence: 99%

Section: ■ Conclusionmentioning

confidence: 93%

Section: ■ Introductionmentioning

confidence: 96%

Section: ■ Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Valence-Bound and Diffuse-Bound Anions of 5-Azauracil

et al. 2014

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“…Recently, investigations on the tautomerism of 5‐azauracil and 6‐azauracil anions were published. However, there are not studies on tautomeric conversions in solution (particularly, water) of neutral azauracils.…”

Section: Introductionmentioning

confidence: 99%

A Hybrid statistical mechanics—quantum chemical model for proton transfer in 5‐azauracil and 6‐azauracil in water solution

Маркова

Pejov

Enchev

2015

Int J of Quantum Chemistry

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A hybrid statistical physics—quantum‐chemical methodology was implemented to study the water‐assisted intramolecular proton‐transfer processes in 5‐ and 6‐azauracils in aqueous solutions. The solvent effects were included in the model by explicit inclusion of two pairs of water molecules, which model the relevant part of the first hydration shell around the solute. The position of these water molecules was initially estimated by carrying out a classical Metropolis of dilute water solutions of the title compounds and subsequently analyzing solute–solvent intermolecular interactions in the Monte Carlo‐generated configurations. Sequentially to the statistical physics simulation, ab initio quantum mechanical (QM) level of theory was implemented. The effects of the water as solvent (at ab initio QM level) were introduced at two different levels—using solute–solvent clusters (four‐water molecules) and using the same clusters embedded in an external continuum. Full geometry optimizations of these complexes were carried out at MP2/6–31 + G(d, p) and conductor‐polarizable continuum model (C‐PCM)/MP2/6–31 + G(d, p). Single point calculations were performed at CCSD(T)/6–31 + G(d, p)//MP2/6–31 + G(d, p) computational level to obtain more accurate energies. According to our calculations hydrated azauracils should exist in three forms: mainly dioxo form and two hydroxy forms. The calculated proton transfer activation energies for tautomeric reactions of 5‐azauracil and 6‐azauracil show different pictures for these two compounds. According to C‐PCM/MP2/6–31 +G(d, p) data, water‐assisted proton transfer in 5‐azauracil realizes through two parallel reactions: 1,3,5‐triazine‐2,4(1H,3H)‐dione → 6‐hydroxy‐1,3,5‐triazin‐2(1H)‐one and 1,3,5‐triazine‐2,4(1H,3H)‐dione → 4‐hydroxy‐1,3,5‐triazin‐2(1H)‐one. Tautomeric equilibrium in 6‐azauracil in water could occur by two contiguous reactions: 1,2,4‐triazine‐3,5(2H,4H)‐dione → 5‐hydroxy‐1,2,4‐triazin‐3(2H)‐one and 5‐hydroxy‐1,2,4‐triazin‐3(2H)‐one → 3‐hydroxy‐1,2,4‐triazin‐5(2H)‐one. The proton transfer investigated reactions in 5‐ and 6‐azauracils involve concerted atomic movement. © 2015 Wiley Periodicals, Inc.

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Electron Propagator Theory

Corzo

Ortiz

2017

Advances in Quantum Chemistry

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Photoelectron Spectroscopy of the 6-Azauracil Anion

Cited by 4 publications

References 54 publications

Valence-Bound and Diffuse-Bound Anions of 5-Azauracil

Valence-Bound and Diffuse-Bound Anions of 5-Azauracil

A Hybrid statistical mechanics—quantum chemical model for proton transfer in 5‐azauracil and 6‐azauracil in water solution

Electron Propagator Theory

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