title: Diffuse Vibrational Signature of a Single Proton Embedded in the Oxalate Scaffold, HO2CCO2(-).
abstract: To understand how the D2d oxalate scaffold (C2O4)(2-) distorts upon capture of a proton, we report the vibrational spectra of the cryogenically cooled HO2CCO2(-) anion and its deuterated isotopologue DO2CCO2(-). The transitions associated with the skeletal vibrations and OH bending modes are sharp and are well described by inclusion of cubic terms in the normal mode expansion of the potential surface through an extended Fermi resonance analysis. The ground state structure features a five-membered ring with an asymmetric intramolecular proton bond. The spectral signatures of the hydrogen stretches, on the contrary, are surprisingly diffuse, and this behavior is not anticipated by the extended Fermi scheme. We trace the diffuse bands to very strong couplings between the high-frequency OH-stretch and the low-frequency COH bends as well as heavy particle skeletal deformations. A simple vibrationally adiabatic model recovers this breadth of oscillator strength as a 0 K analogue of the motional broadening commonly used to explain the diffuse spectra of H-bonded systems at elevated temperatures, but where these displacements arise from the configurations present at the vibrational zero-point level.
authors.affiliation: Sterling Chemistry Laboratory, Yale University , New Haven, Connecticut 06520, United States.
authors.forename: Conrad T
authors.initials: CT
authors.lastname: Wolke
authors.affiliation: Sterling Chemistry Laboratory, Yale University , New Haven, Connecticut 06520, United States.|Department of Chemistry, Purdue University , West Lafayette, Indiana 47907, United States.
authors.forename: Andrew F
authors.initials: AF
authors.lastname: DeBlase
authors.affiliation: Sterling Chemistry Laboratory, Yale University , New Haven, Connecticut 06520, United States.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Leavitt
authors.affiliation: Department of Chemistry, University of Washington , Seattle, Washington 98195, United States.
authors.forename: Anne B
authors.initials: AB
authors.lastname: McCoy
authors.affiliation: Sterling Chemistry Laboratory, Yale University , New Haven, Connecticut 06520, United States.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Johnson