HIGH RESOLUTION FLUORESCENCE EXCITATION SPECTRA OF THE 1- AND 2- HYDROXYNAPHTHALENES. DISTINGUISHING THE CIS AND TRANS $ROTAMERS.^{1}$
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Date
1989
Journal Title
Journal ISSN
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Publisher
Ohio State University
Abstract
It has been previously reported that the $S_{1}-S_{0}$ fluorescence excitation and absorption spectra of the 1- and 2-naphthols can be interpreted by assuming the existence of cis and trans rotamers, each with their own $0^{o}_{o}$ bands and vibrational $progressions.^{2,3}$ However, the evidence for the existence of these rotamers, and the assignment of a particular origin and progression to a specific rotamer, is indirect and inconclusive. We have examined several bands of 1- and 2- naphthol (OH and OD) at high resolution using LIF and a molecular beam. With linewidths on the order of 5 MHz, each band consists of $2000^{+}$ resolved rotational lines, and changes in the rotational constants due to the different geometrics of the two rotamers can be detected. We have also performed molecular orbital calculations on the $S_{0}$ and $S_{1}$ states at the single configuration Hartree-Fock level. Taken together, the results give an unambiguous proof of the existence of the different rotamers, an assignment of their spectra, and the key geometry changes that occur in the naphthois upon electronic excitation.
Description
$^{1}$ Work supported by NSF. $^{2}$ A Oikawa. H. Abe. N. Mikami. M. Ito. J. Phys. Chem. 88 5180 (1984). $^{3}$ J. M. Hollas. M. Z. B. Hussein. J. Mol. Spectrosc. 127 497 (1988).
Author Institution: Department of Chemistry, University of Pittsburgh.
Author Institution: Department of Chemistry, University of Pittsburgh.