title: Subtle solvation behaviour of a biofuel additive: the methanol complex with 2,5-dimethylfuran.
abstract: Methanol is shown to engage two nearly equivalent solvation sites in 2,5-dimethylfuran, the electron-rich π cloud and the electron-deficient oxygen site. The latter only wins by a slight margin, thanks to the methyl group undergoing secondary interactions with the ring. These secondary attractions reduce the hydrogen bond-induced OH frequency shift of the OH-O contact, whereas the π cloud allows for a combined action of both binding mechanisms in the OH-π arrangement. In total, the hydrophobic character of 2,5-dimethylfuran is well reflected in the weak pair interactions, as judged by the small solvation shifts. Methanol solvation of 2,3-benzofuran is revisited and shown to be more ambiguous than previously thought, involving competition between five- and six-ring π clouds and the oxygen site for the OH group. The six-ring π cloud is slightly preferred. FTIR spectroscopy in supersonic jets is in systematic agreement with dispersion-corrected harmonic B3LYP and also B2PLYP predictions for these competing furan docking sites. Deuteration of the OH group helps to identify the docking sites because of its attenuated zero-point energy weakening effect on localized hydrogen bonds. Extension to less methylated furans is proposed in the context of a future forecasting competition for the performance of quantum chemical methods for intermolecular interactions.
authors.affiliation: Institut für Physikalische Chemie, Universität Göttingen, Tammannstr. 6, 37077 Göttingen, Germany. msuhm@gwdg.de.
authors.forename: Anja
authors.initials: A
authors.lastname: Poblotzki
authors.affiliation: Institut für Physikalische Chemie, Universität Göttingen, Tammannstr. 6, 37077 Göttingen, Germany. msuhm@gwdg.de.
authors.forename: Jonas
authors.initials: J
authors.lastname: Altnöder
authors.affiliation: Institut für Physikalische Chemie, Universität Göttingen, Tammannstr. 6, 37077 Göttingen, Germany. msuhm@gwdg.de.
authors.forename: Martin A
authors.identifier: http://orcid.org/0000-0001-8841-7705
authors.initials: MA
authors.lastname: Suhm