Tags

Type your tag names separated by a space and hit enter

Two competitive routes in the lactim-lactam phototautomerization of a hydroxypyridine derivative cation in water: dissociative mechanism versus water-assisted proton transfer.
J Phys Chem A. 2005 Nov 17; 109(45):10189-98.JP

Abstract

Ground-state tautomerism and excited-state proton-transfer processes of 2-(6'-hydroxy-2'-pyridyl)benzimidazolium in H2O and D2O have been studied by means of UV-vis absorption and fluorescence spectroscopy in both steady-state and time-resolved modes. In the ground state, this compound shows a tautomeric equilibrium between the lactim cation, protonated at the benzimidazole N3, and its lactam tautomer, obtained by proton translocation from the hydroxyl group to the pyridine nitrogen. Direct excitation of the lactam tautomer leads to its own fluorescence emission, while as a result of the increase of acidity of the OH group and basicity at the pyridine N upon excitation, the lactim species undergoes a proton translocation from the hydroxyl group to the nitrogen, favoring the lactam structure in the excited state. No fluorescence emission from the initially excited lactim species was detected due to the ultrafast rate of the excited-state proton-transfer processes. The lactim-lactam phototaumerization process takes place via two competitive excited-state proton-transfer routes: a one-step water-assisted proton translocation (probably a double proton transfer) and a two-step pathway which involves first the dissociation of the lactim cation to form an emissive intermediate zwitterionic species and then the acid-catalyzed protonation at the pyridine nitrogen to give rise to the lactam tautomer.

Authors+Show Affiliations

Departamento de Química Física, Facultade de Química, Universidade de Santiago de Compostela, E-15782 Santiago de Compostela, Spain.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

16833311

Citation

Penedo, J Carlos, et al. "Two Competitive Routes in the Lactim-lactam Phototautomerization of a Hydroxypyridine Derivative Cation in Water: Dissociative Mechanism Versus Water-assisted Proton Transfer." The Journal of Physical Chemistry. A, vol. 109, no. 45, 2005, pp. 10189-98.
Penedo JC, Rodríguez MC, Lema IG, et al. Two competitive routes in the lactim-lactam phototautomerization of a hydroxypyridine derivative cation in water: dissociative mechanism versus water-assisted proton transfer. J Phys Chem A. 2005;109(45):10189-98.
Penedo, J. C., Rodríguez, M. C., Lema, I. G., Lustres, J. L., Mosquera, M., & Rodríguez-Prieto, F. (2005). Two competitive routes in the lactim-lactam phototautomerization of a hydroxypyridine derivative cation in water: dissociative mechanism versus water-assisted proton transfer. The Journal of Physical Chemistry. A, 109(45), 10189-98.
Penedo JC, et al. Two Competitive Routes in the Lactim-lactam Phototautomerization of a Hydroxypyridine Derivative Cation in Water: Dissociative Mechanism Versus Water-assisted Proton Transfer. J Phys Chem A. 2005 Nov 17;109(45):10189-98. PubMed PMID: 16833311.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Two competitive routes in the lactim-lactam phototautomerization of a hydroxypyridine derivative cation in water: dissociative mechanism versus water-assisted proton transfer. AU - Penedo,J Carlos, AU - Rodríguez,M Carmen Ríos, AU - Lema,Iria García, AU - Lustres,J Luis Pérez, AU - Mosquera,Manuel, AU - Rodríguez-Prieto,Flor, PY - 2006/7/13/pubmed PY - 2007/7/26/medline PY - 2006/7/13/entrez SP - 10189 EP - 98 JF - The journal of physical chemistry. A JO - J Phys Chem A VL - 109 IS - 45 N2 - Ground-state tautomerism and excited-state proton-transfer processes of 2-(6'-hydroxy-2'-pyridyl)benzimidazolium in H2O and D2O have been studied by means of UV-vis absorption and fluorescence spectroscopy in both steady-state and time-resolved modes. In the ground state, this compound shows a tautomeric equilibrium between the lactim cation, protonated at the benzimidazole N3, and its lactam tautomer, obtained by proton translocation from the hydroxyl group to the pyridine nitrogen. Direct excitation of the lactam tautomer leads to its own fluorescence emission, while as a result of the increase of acidity of the OH group and basicity at the pyridine N upon excitation, the lactim species undergoes a proton translocation from the hydroxyl group to the nitrogen, favoring the lactam structure in the excited state. No fluorescence emission from the initially excited lactim species was detected due to the ultrafast rate of the excited-state proton-transfer processes. The lactim-lactam phototaumerization process takes place via two competitive excited-state proton-transfer routes: a one-step water-assisted proton translocation (probably a double proton transfer) and a two-step pathway which involves first the dissociation of the lactim cation to form an emissive intermediate zwitterionic species and then the acid-catalyzed protonation at the pyridine nitrogen to give rise to the lactam tautomer. SN - 1089-5639 UR - https://www.unboundmedicine.com/medline/citation/16833311/Two_competitive_routes_in_the_lactim_lactam_phototautomerization_of_a_hydroxypyridine_derivative_cation_in_water:_dissociative_mechanism_versus_water_assisted_proton_transfer_ L2 - https://doi.org/10.1021/jp0518355 DB - PRIME DP - Unbound Medicine ER -