Vibrational Structure and Dynamics of p-Cresol Dimer from the Excitation Spectrum
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Date
1990
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Ohio State University
Abstract
The fluorescence excitation spectrum of p-Cresol dimer displays over 20 vibrational transitions in the first $50 cm^{-1}$ of the spectrum. Most of these can be assigned as combinations and overtones of two nearly harmonic modes of 8.5 and $13 cm^{-1}$ which are atbtuted to the intermolecular bend and torsion. The spectrum also exhibits a $109 cm^{-1}$ mode and its overtone at $217 cm^{-1}$ which are due to the the intermolecular stretch, but shows no transitions above $450 cm^{-1}$. This is in sharp contrast to the p-crasol H2O spectrum which displays prominant ring modes up to $800 cm^{-1}$. Comparison of the dimer and water complex hydrogen bond strengths by use of their stretching frequendes and a crude dialomic model shows the H bonding to be appreciably stronger in the dimer. Thus the lack of intesity above $450 cm^{-1}$ in the dimer spectrum cannot be attributed to direct dissociation of the dimer, but is most liky due to IVR which may then be followed by dissociation.
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Author Institution: Department of Chemistry, Moniana State University