title: Communication: The ionization spectroscopy of mixed carboxylic acid dimers.
abstract: We report mass analyzed threshold ionization spectroscopy of supersonically cooled gas phase carboxylic complexes with 9-hydroxy-9-fluorenecarboxylic acid (9HFCA), an analog of glycolic acid. The vibrationally resolved cation spectrum for the 9HFCA complex with formic acid allows accurate determination of its ionization potential (IP), 64,374 ± 8 cm(-1). This is 545 cm(-1) smaller than the IP of 9HFCA monomer. The IPs of 9HFCA complexes with acetic acid and benzoic acid shift by -1133 cm(-1) and -1438 cm(-1), respectively. Density functional calculations confirm that Cs symmetry is maintained upon ionization of the 9HFCA monomer and its acid complexes, in contrast to the drastic geometric rearrangement attending ionization in complexes of 9-fluorene carboxylic acid. We suggest that the marginal geometry changes and small IP shifts are primarily due to the collective interactions among one intramolecular and two intermolecular hydrogen bonds in the dimer.
authors.affiliation: School of Basic Medical Sciences, Xinxiang Medical University, Xinxiang, Henan 453003, China.
authors.forename: Zhijun
authors.initials: Z
authors.lastname: Yang
authors.forename: Quanli
authors.initials: Q
authors.lastname: Gu
authors.forename: Carl O
authors.initials: CO
authors.lastname: Trindle
authors.forename: J L
authors.initials: JL
authors.lastname: Knee