title: The influence of large-amplitude librational motion on the hydrogen bond energy for alcohol-water complexes.
abstract: The far-infrared absorption spectra have been recorded for hydrogen-bonded complexes of water with methanol and t-butanol embedded in cryogenic neon matrices at 2.8 K. The partial isotopic substitution of individual subunits enabled by a dual inlet deposition procedure provides for the first time unambiguous assignments of the intermolecular high-frequency out-of-plane and low-frequency in-plane donor OH librational modes for mixed alcohol-water complexes. The vibrational assignments confirm directly that water acts as the hydrogen bond donor in the most stable mixed complexes and the tertiary alcohol is a superior hydrogen bond acceptor. The class of large-amplitude donor OH librational motion is shown to account for up to 5.1 kJ mol(-1) of the destabilizing change of vibrational zero-point energy upon intermolecular OHO hydrogen bond formation. The experimental findings are supported by complementary electronic structure calculations at the CCSD(T)-F12/aug-cc-pVTZ level of theory.
authors: Department of Chemistry, Technical University of Denmark, Kemitorvet 206, 2800 Kgs. Lyngby, Denmark. rewl@kemi.dtu.dk.
authors: J
authors: J
authors: Andersen
authors: J
authors: J
authors: Heimdal
authors: R
authors: R
authors: Wugt Larsen
mesh_terms: D000438:Alcohols / Q000737:chemistry*; D006860:Hydrogen Bonding; D009038:Motion; D011789:Quantum Theory; D014867:Water / Q000737:chemistry*
chemical_list: D000438:Alcohols; D014867:Water