title: Acetic acid-water complex: The first observation of structures containing the higher-energy acetic acid conformer.
abstract: Non-covalent interaction of acetic acid (AA) and water is studied experimentally by IR spectroscopy in a nitrogen matrix and theoretically at the MP2 and coupled-cluster with single and double and perturbative triple excitations [CCSD(T)]/6-311++G(2d,2p) levels of theory. This work is focused on the first preparation and characterization of complexes of higher-energy (cis) conformer of AA with water. The calculations show three 1:1 structures for the trans-AA⋯H2O complexes and three 1:1 structures for the cis-AA⋯H2O complexes. Two trans-AA⋯H2O and two cis-AA⋯H2O complexes are found and structurally assigned in the experiments. The two cis-AA⋯ ⋅ H2O complexes are obtained by annealing of a matrix containing water and cis-AA molecules prepared by selective vibrational excitation of the ground-state trans form. The less stable trans-AA⋯H2O complex is obtained by vibrational excitation of the less stable cis-AA⋯H2O complex. In addition, the 1:2 complexes of trans-AA and cis-AA with water molecules are studied computationally and the most stable forms of the 1:2 complexes are experimentally identified.
authors.affiliation: CQC, Department of Chemistry, University of Coimbra, Rua Larga, P-3004-535 Coimbra, Portugal.
authors.forename: Susy
authors.initials: S
authors.lastname: Lopes
authors.affiliation: CQC, Department of Chemistry, University of Coimbra, Rua Larga, P-3004-535 Coimbra, Portugal.
authors.forename: Rui
authors.initials: R
authors.lastname: Fausto
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