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Steric control of the excited-state intramolecular proton transfer in 3-hydroxyquinolones: steady-state and time-resolved fluorescence study.
J Phys Chem A. 2007 Sep 20; 111(37):8986-92.JP

Abstract

3-Hydroxyquinolones (3HQs), similarly to their 3-hydroxychromone analogs, undergo excited state intramolecular proton transfer (ESIPT) resulting in dual emission. In the ground state, 2-phenyl-3HQ derivatives are not flat due to a steric hindrance between the 2-phenyl group and the 3-OH group that participates in the ESIPT reaction. To study the effect of this steric hindrance on the ESIPT reaction, a number of 3HQ derivatives have been synthesized and characterized in different organic solvents by steady-state and time-resolved fluorescence techniques. According to our results, 2-phenyl-3HQ derivatives undergo much faster ESIPT (by nearly 1 order of magnitude) than their 2-methyl-3HQ analogs. Moreover, 1-methyl-2-phenyl-3HQ having a strongly twisted 2-phenyl group undergoes a two- to three-fold slower ESIPT compared to 2-phenyl-3HQ. These results suggest that the flatter conformation of 2-phenyl-3HQ, which allows a close proximity of the 2-phenyl and 3-OH groups, favors a fast ESIPT reaction. The absorption and fluorescence spectra of the 3HQ derivatives additionally confirm that the steric rather than the electronic effect of the 2-phenyl group is responsible for the faster ESIPT reaction. Based on the spectroscopic studies and quantum chemical calculations, we suggest that the 2-phenyl group decreases the rotational freedom of its proximal 3-OH group in the more planar conformation of 2-phenyl-3HQ. As a result, the conformations of 3HQ, where the 3-OH group orients to form an intramolecular H-bond with the 4-carbonyl group, are favored over those with a disrupted intramolecular H-bond. Therefore, the 2-phenyl group sterically favors the intramolecular H-bond and thus accelerates the ESIPT reaction. This conclusion provides a new understanding of the ESIPT process in 3-hydroxyquinolones and related systems and suggests new possibilities for the design of ESIPT based molecular sensors and switchers.

Authors+Show Affiliations

Department of Chemistry, Kyiv National Taras Shevchenko University, 01033 Kyiv, Ukraine. dmytro@pharma.u-strasbg.frNo 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

17718453

Citation

Yushchenko, Dmytro A., et al. "Steric Control of the Excited-state Intramolecular Proton Transfer in 3-hydroxyquinolones: Steady-state and Time-resolved Fluorescence Study." The Journal of Physical Chemistry. A, vol. 111, no. 37, 2007, pp. 8986-92.
Yushchenko DA, Shvadchak VV, Klymchenko AS, et al. Steric control of the excited-state intramolecular proton transfer in 3-hydroxyquinolones: steady-state and time-resolved fluorescence study. J Phys Chem A. 2007;111(37):8986-92.
Yushchenko, D. A., Shvadchak, V. V., Klymchenko, A. S., Duportail, G., Pivovarenko, V. G., & Mély, Y. (2007). Steric control of the excited-state intramolecular proton transfer in 3-hydroxyquinolones: steady-state and time-resolved fluorescence study. The Journal of Physical Chemistry. A, 111(37), 8986-92.
Yushchenko DA, et al. Steric Control of the Excited-state Intramolecular Proton Transfer in 3-hydroxyquinolones: Steady-state and Time-resolved Fluorescence Study. J Phys Chem A. 2007 Sep 20;111(37):8986-92. PubMed PMID: 17718453.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Steric control of the excited-state intramolecular proton transfer in 3-hydroxyquinolones: steady-state and time-resolved fluorescence study. AU - Yushchenko,Dmytro A, AU - Shvadchak,Volodymyr V, AU - Klymchenko,Andrey S, AU - Duportail,Guy, AU - Pivovarenko,Vasyl G, AU - Mély,Yves, Y1 - 2007/08/24/ PY - 2007/8/28/pubmed PY - 2007/11/10/medline PY - 2007/8/28/entrez SP - 8986 EP - 92 JF - The journal of physical chemistry. A JO - J Phys Chem A VL - 111 IS - 37 N2 - 3-Hydroxyquinolones (3HQs), similarly to their 3-hydroxychromone analogs, undergo excited state intramolecular proton transfer (ESIPT) resulting in dual emission. In the ground state, 2-phenyl-3HQ derivatives are not flat due to a steric hindrance between the 2-phenyl group and the 3-OH group that participates in the ESIPT reaction. To study the effect of this steric hindrance on the ESIPT reaction, a number of 3HQ derivatives have been synthesized and characterized in different organic solvents by steady-state and time-resolved fluorescence techniques. According to our results, 2-phenyl-3HQ derivatives undergo much faster ESIPT (by nearly 1 order of magnitude) than their 2-methyl-3HQ analogs. Moreover, 1-methyl-2-phenyl-3HQ having a strongly twisted 2-phenyl group undergoes a two- to three-fold slower ESIPT compared to 2-phenyl-3HQ. These results suggest that the flatter conformation of 2-phenyl-3HQ, which allows a close proximity of the 2-phenyl and 3-OH groups, favors a fast ESIPT reaction. The absorption and fluorescence spectra of the 3HQ derivatives additionally confirm that the steric rather than the electronic effect of the 2-phenyl group is responsible for the faster ESIPT reaction. Based on the spectroscopic studies and quantum chemical calculations, we suggest that the 2-phenyl group decreases the rotational freedom of its proximal 3-OH group in the more planar conformation of 2-phenyl-3HQ. As a result, the conformations of 3HQ, where the 3-OH group orients to form an intramolecular H-bond with the 4-carbonyl group, are favored over those with a disrupted intramolecular H-bond. Therefore, the 2-phenyl group sterically favors the intramolecular H-bond and thus accelerates the ESIPT reaction. This conclusion provides a new understanding of the ESIPT process in 3-hydroxyquinolones and related systems and suggests new possibilities for the design of ESIPT based molecular sensors and switchers. SN - 1089-5639 UR - https://www.unboundmedicine.com/medline/citation/17718453/Steric_control_of_the_excited_state_intramolecular_proton_transfer_in_3_hydroxyquinolones:_steady_state_and_time_resolved_fluorescence_study_ L2 - https://doi.org/10.1021/jp071075t DB - PRIME DP - Unbound Medicine ER -