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Title: Spectroscopic identification of ethanol-water conformers by large-amplitude hydrogen bond librational modes

The far-infrared absorption spectra have been recorded for hydrogen-bonded complexes of water with ethanol embedded in cryogenic neon matrices at 2.8 K. The partial isotopic H/D-substitution of the ethanol subunit enabled by a dual inlet deposition procedure enables the observation and unambiguous assignment of the intermolecular high-frequency out-of-plane and the low-frequency in-plane donor OH librational modes for two different conformations of the mixed binary ethanol/water complex. The resolved donor OH librational bands confirm directly previous experimental evidence that ethanol acts as the O⋯HO hydrogen bond acceptor in the two most stable conformations. In the most stable conformation, the water subunit forces the ethanol molecule into its less stable gauche configuration upon dimerization owing to a cooperative secondary weak O⋯HC hydrogen bond interaction evidenced by a significantly blue-shift of the low-frequency in-plane donor OH librational band origin. The strong correlation between the low-frequency in-plane donor OH librational motion and the secondary intermolecular O⋯HC hydrogen bond is demonstrated by electronic structure calculations. The experimental findings are further supported by CCSD(T)-F12/aug-cc-pVQZ calculations of the conformational energy differences together with second-order vibrational perturbation theory calculations of the large-amplitude donor OH librational band origins.
Authors:
;  [1] ;  [2]
  1. Department of Chemistry, Technical University of Denmark, Kemitorvet 206, 2800 Kongens Lyngby (Denmark)
  2. MAX-IV Laboratory, Lund University, P.O. Box 118, 22100 Lund (Sweden)
Publication Date:
OSTI Identifier:
22493321
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 143; Journal Issue: 22; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ABSORPTION SPECTRA; ALLOCATIONS; AMPLITUDES; CHEMICAL BONDS; COMPLEXES; COOPERATIVES; CORRELATIONS; DEPOSITION; DIMERIZATION; ELECTRONIC STRUCTURE; ETHANOL; HYDROGEN; MOLECULES; NEON; PERTURBATION THEORY; WATER