title: Acetic acid dimers in a nitrogen matrix: Observation of structures containing the higher-energy conformer.
abstract: Acetic acid (AA) dimers are studied experimentally by infrared spectroscopy in a N2 matrix and theoretically at the MP2/6-311++G(2d,2p) level of approximation. This work is focused on the first preparation and characterization of structures containing the higher-energy (cis) conformer of AA. Nine trans-trans, fourteen trans-cis, and six cis-cis dimers are theoretically predicted. Five trans-trans and a number of trans-cis dimers are identified in the experiments, but no indication of cis-cis dimers is found. Two trans-trans dimers and the trans-cis dimers are reported for the first time. One trans-cis dimer is prepared by selective vibrational excitation of the structurally related trans-trans dimer, which converts one of the trans subunits to the cis form. Several trans-cis dimers are obtained by annealing of a matrix containing both trans and cis monomers of AA. Tunneling-induced conversion of the trans-cis dimers into trans-trans forms (including two new trans-trans forms) is observed at low temperatures.
authors.affiliation: Department of Chemistry, University of Coimbra, Rua Larga, P-3004-535 Coimbra, Portugal.
authors.forename: Susy
authors.initials: S
authors.lastname: Lopes
authors.affiliation: Institute of Physical Chemistry, Georg-August University, Tammannstr 6, D-37077 Göttingen, Germany.
authors.forename: Alexandra V
authors.initials: AV
authors.lastname: Domanskaya
authors.affiliation: Department of Chemistry, University of Helsinki, P.O. Box 55, FI-00014 Helsinki, Finland.
authors.forename: Markku
authors.initials: M
authors.lastname: Räsänen
authors.affiliation: Department of Chemistry, University of Helsinki, P.O. Box 55, FI-00014 Helsinki, Finland.
authors.forename: Leonid
authors.initials: L
authors.lastname: Khriachtchev
authors.affiliation: Department of Chemistry, University of Coimbra, Rua Larga, P-3004-535 Coimbra, Portugal.
authors.forename: Rui
authors.initials: R
authors.lastname: Fausto
mesh_terms: D019342:Acetic Acid / Q000737:chemistry*; D019281:Dimerization; D006860:Hydrogen Bonding; D008956:Models, Chemical; D015394:Molecular Structure; D009584:Nitrogen / Q000737:chemistry*; D011789:Quantum Theory; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature; D014732:Vibration
chemical_list: D009584:Nitrogen; D019342:Acetic Acid