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Spectral tuning by switching C–H...O hydrogen bonds: Rotation-induced spectral shifts of 7-hydroxyquinoline·HCOOH isomers.
- Source :
- Journal of Chemical Physics; 1/14/2008, Vol. 128 Issue 2, p024304, 13p, 4 Diagrams, 5 Charts, 9 Graphs
- Publication Year :
- 2008
-
Abstract
- Spectral tuning effects on visible chromophores by hydrogen bonds are central to the chemistry of vision and of photosynthesis. A model for large spectral tuning effects by hydrogen bond switching is provided by the 7-hydroxyquinoline·HCOOH complex, which forms two isomers, CTN1 and CTN2, both with an HCOOH...N hydrogen bond but with different (quinoline)C–H...O==C hydrogen bonds. A 180° rotation of the HCOOH moiety around the O–H...N hydrogen bond exchanges the C–H...O hydrogen bonds, rotates the dipole moment of HCOOH, and leads to an ∼850 cm<superscript>-1</superscript> shift of the electronic spectrum. Mass-selected S<subscript>1</subscript>←S<subscript>0</subscript> resonant two-photon ionization, UV-UV holeburning, S<subscript>1</subscript>→S<subscript>0</subscript> fluorescence spectra, and photoionization efficiency curves of the two 7-hydroxyquinoline·HCOOH isomers were measured in supersonic expansions. Comparison to ab initio calculations allow us to determine the H-bond connectivity and structure of the two isomers and to assign their inter- and intramolecular vibrations. The Franck-Condon factors of the intermolecular shear vibration χ in the S<subscript>1</subscript>←S<subscript>0</subscript> spectra indicate that the weak C–H...O hydrogen bond contracts markedly in the CTN1 isomer but expands in the CTN2 isomer. These changes of H-bond lengths agree with the spectral shifts. In contrast, the strong O–H...N hydrogen bond undergoes little change upon S<subscript>1</subscript>←S<subscript>0</subscript> excitation. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00219606
- Volume :
- 128
- Issue :
- 2
- Database :
- Complementary Index
- Journal :
- Journal of Chemical Physics
- Publication Type :
- Academic Journal
- Accession number :
- 28528050
- Full Text :
- https://doi.org/10.1063/1.2816710