To pi or not to pi - how does methanol dock onto anisole?

To pi or not to pi - how does methanol dock onto anisole?
Heger, M.; Altnoeder, J.; Poblotzki, A. & Suhm, M. A.  (2015) 
Physical Chemistry Chemical Physics17(19) pp. 13045-13052.​

Authors
Heger, Matthias; Altnoeder, Jonas; Poblotzki, Anja; Suhm, Martin A. 
Issue Date
2015
Type
Journal Article
Publisher
Royal Soc Chemistry
Journal
Physical Chemistry Chemical Physics 
Organization
Institut für Physikalische Chemie 
ISSN
1463-9084; 1463-9076
Abstract
Anisole offers two similarly attractive hydrogen bond acceptor sites to an incoming hydrogen bond donor: its oxygen atom and its delocalized pi electron system. Electronic structure calculations up to the CCSD(T)/AVTZ level suggest an isoenergetic situation for methanol after harmonic zero point energy correction, within less than 1 kJ mol(-1). Linear infrared absorption spectroscopy in the OH stretching fundamental range applied to a cold supersonic jet expansion of anisole and methanol in helium shows that the oxygen binding site is preferred, with about 20 times less pi-bonded than O-bonded dimers despite the non-equilibrium collisional environment. Accidental band overlap is ruled out by OH overtone and OD stretching spectroscopy. Furthermore, the diagonal anharmonicity constant of the OH stretching mode is derived from experiment and reaches 80% of the monomer distortion found in the methanol dimer, as expected for a weaker hydrogen bond to the aromatically substituted oxygen. To reconcile these experimental findings with ab initio theory, accurate nuclear and electronic structure calculations involving AVQZ basis sets are required. Dispersion-corrected double-hybrid density functional theory provides a less expensive successful structural approach.
Publication of Göttingen University
Yes
Sponsor
Funder: Deutsche Forschungsgemeinschaft (DFG) [SU 121/4, SPP 1807]
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