Conformational effects on vibronic spectra and excited state dynamics of 3-fluorobenzoic acid dimer

The Journal of Chemical Physics
Chayan K NandiTapas Chakraborty

Abstract

Two conformational isomers of 3-fluorobenzoic acid dimer (3-FBA(2)) have been identified in a supersonic jet expansion by use of laser-induced fluorescence excitation (FE), UV-UV hole-burning, and dispersed fluorescence (DF) spectroscopic methods. In the FE spectrum, the S(1) origins of the two isomeric species appear at a frequency gap of only 24 cm(-1), and the vibronic intensities of the redshifted dimer (dimer I) are about two times weaker than those of dimer II. However, ab initio quantum chemistry calculations at the MP2/6-31G(**) level of theory predict that all the isomeric species of 3-FBA(2) have almost the same binding energy (approximately 17 kcal/mol) in the ground state. Furthermore, unlike benzoic acid dimer, the present system shows intense activity for a low-frequency mode in both the FE and DF spectra. With the aid of DFT (B3LYP/6-311G(**)) predicted normal mode frequencies, we have assigned the mode to the in-plane gear (cogwheel) vibration of the cyclic hydrogen-bonded frame of the dimer. The Franck-Condon profiles for vibronic excitation of the mode indicate that the distortion of the cyclic hydrogen bond frame as a result of S(1)<--S(0) excitation is larger for dimer I than dimer II. Moreover, the fluoresc...Continue Reading

References

Feb 6, 1999·Annual Review of Physical Chemistry·R I Cukier, D G Nocera
Jul 23, 2004·The Journal of Chemical Physics·Chayan K Nandi, Tapas Chakraborty

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Citations

Jan 6, 2006·The Journal of Chemical Physics·Chayan K NandiTapas Chakraborty
Jun 11, 2005·The Journal of Chemical Physics·Asier LongarteFernando Castaño
Jul 30, 2008·Chemphyschem : a European Journal of Chemical Physics and Physical Chemistry·Ivo KalkmanW Leo Meerts
Jul 13, 2006·The Journal of Physical Chemistry. a·Juan LiWei-Hai Fang

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