Collect. Czech. Chem. Commun. 2009, 74, 167-188
Published online 2009-02-11 10:56:18

Bonding between the cesium cation and substituted benzoic acids or benzoate anions in the gas phase: A density functional theory and mass spectrometric study

Charly Mayeuxa, Lionel Massia, Jean-François Gala,*, Pierre-Charles Mariaa, Jaana Tammiku-Taulb, Ene-Liis Lohub and Peeter Burkb,*

a Laboratoire de Radiochimie, Sciences Analytiques et Environnement, and Plate-forme Technologique-Spectrométrie de Masse, Institute of Chemistry of Nice (FR CNRS 3037), University of Nice-Sophia Antipolis, 06108 Nice Cedex 2, France
b Institute of Chemistry, University of Tartu, Jakobi 2, 51014 Tartu, Estonia


Substituent effects on the formation of cesium cation complexes with a series of 17 benzoic acids (AH), benzoates (A), and the ion pairs (Cs+A) are studied by density functional theory (DFT) and mass spectrometry. This study is positioned in the context of the fate of cesium in the environment, with emphasis of the influence of natural organic matter and humic substances. The bond length Cs+-(carboxylic O) in the various adduct geometries are discussed as regards the interaction strength, but quantitative relationships are limited by secondary effects arising mostly from long-distance interactions in systems bearing polar groups in meta-position. Relative cesium cation affinities of [Cs+A] were experimentally determined by the kinetic method, i.e. by dissociating the required cesium cluster formed by electrospray ionization in a quadrupole ion-trap. Experiments and calculations are in agreement, except for the adducts derived from 3- and 4-hydroxybenzoic acids. A change in the localization of the negative charge is proposed as a possible explanation for the divergence.

Keywords: Cesium cation; Affinity; Basicity; Gas phase; DFT calculations; Mass spectrometry; Substituent effects; Benzoic acids.

References: 56 live references.