title: Probing the low-barrier hydrogen bond in hydrogen maleate in the gas phase: a photoelectron spectroscopy and ab initio study.
abstract: The strength of the low-barrier hydrogen bond in hydrogen maleate in the gas phase was investigated by low-temperature photoelectron spectroscopy and ab initio calculations. Photoelectron spectra of maleic and fumaric acid monoanions (cis-/trans-HO(2)CCH=CHCO(2)(-)) were obtained at low temperatures and at 193 nm photon energy. Vibrational structure was observed for trans-HO(2)CCH=CHCO(2)(-) due to the OCO bending modes; however, cis-HO(2)CCH=CHCO(2)(-) yielded a broad and featureless spectrum. The electron binding energy of cis-HO(2)CCH=CHCO(2)(-) is about 1 eV blue-shifted relative to trans-HO(2)CCH=CHCO(2)(-) due to the formation of intramolecular hydrogen bond in the cis-isomer. Theoretical calculations (CCSD(T)/ aug-cc-pVTZ and B3LYP/aug-cc-pVTZ) were carried out to estimate the strength of the intramolecular hydrogen bond in cis-HO(2)CCH=CHCO(2)(-). Combining experimental and theoretical calculations yields an estimate of 21.5 +/- 2.0 kcal/mol for the intramolecular hydrogen bond strength in hydrogen maleate.
authors.forename: Hin-Koon
authors.initials: HK
authors.lastname: Woo
authors.forename: Xue-Bin
authors.initials: XB
authors.lastname: Wang
authors.forename: Lai-Sheng
authors.initials: LS
authors.lastname: Wang
authors.forename: Kai-Chung
authors.initials: KC
authors.lastname: Lau
mesh_terms: D055598:Chemical Phenomena; D002627:Chemistry, Physical; D005650:Fumarates / Q000737:chemistry; D005740:Gases / Q000737:chemistry*; D006860:Hydrogen Bonding; D008298:Maleates / Q000737:chemistry*; D008968:Molecular Conformation; D015394:Molecular Structure; D013057:Spectrum Analysis
chemical_list: D005650:Fumarates; D005740:Gases; D008298:Maleates; C032005:fumaric acid; C030272:maleic acid