THE TEMPERATURE AND SURROUNDINGS DEPENDENT NONHARMONIC IR VIBRATIONAL SPECTRUM OF TROPOLONE
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Date
1999
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Ohio State University
Abstract
Infrared spectra are reported for tropolone in the vapor phase near 350 K, and dissolved in $CS_{2}$ and $CCl_{4}$ solvents near 300 K. These results are compared with IR spectra of tropolone suspended in Ar and Ne matrices near 5 K, and with fluorescence-dip IR spectra in the $3000 cm^{-1}$ region obtained by the Zwier group for jet-cooled tropolone. The collected experiments reveal temperature and surroundings dependent transitions. Comparisons of the observed frequencies and intensities with harmonic spectra predicted by MO computation (B3LYP and MP2) using 6-311G(df,pd) and 6-311G(d,p) basis sets for the OCCOH ring and $C_{5}H_{5}$ loop, respectively, suggest a broad spectral landscape of nonharmonic behavior by tropolone. MO computation at the above level reduces the energy of the $C_{2v}$ saddle-point configuration to only 3.64 kcal/mol above that of the optimized geometry. The results are believed to suggest that in its electronic ground state tropolone tunnels between its two equivalent PES minima via a complex multidimensional process depending strongly on heavy atom skeletal motions.
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Author Institution: Department of Chemistry and Biochemistry, Texas Tech University