Cooperativity in ionic liquids

Simone Kossmann; Jens Thar; Barbara Kirchner; Patricia A Hunt; Tom Welton

doi:10.1063/1.2191493

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Cooperativity in ionic liquids

Simone Kossmann, Jens Thar, Barbara Kirchner, Patricia A Hunt and Tom Welton

The Journal of chemical physics, Vol.124(17), pp.174506-174506-12

05/07/2006

DOI: https://doi.org/10.1063/1.2191493

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https://hdl.handle.net/2376/114729

PMID: 16689582

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Abstract

Cooperativity in ionic liquids is investigated by means of static quantum chemical calculations. Larger clusters of the dimethylimidazolium cation paired with a chloride anion are calculated within density functional theory combined with gradient corrected functionals. Tests of the monomer unit show that density functional theory performs reasonably well. Linear chain and ring aggregates have been considered and geometries are found to be comparable with liquid phase structures. Cooperative effects occur when the total energy of the oligomer differs from a simple sum of monomer energies. Cooperative effects have been found in the structural motifs examined. A systematic study of linear chains of increasing length (up to nine monomer units) has shown that cooperativity plays a more important role than expected and is stronger than in water. The Cl...H distance of the chloride to the most acidic proton increases with an increasing number of monomer units. The average bond distance approaches 218.9 pm asymptotically. The dipole moment grows almost linearly and the dipole moment per monomer unit reaches the asymptotic value of 16.3 D. The charge on the chloride atoms decreases with an increasing chain length. In order to detect local hydrogen bonding in the clusters a new parametrization of the shared-electron number method is introduced. We find decreasing hydrogen bond energies with an increasing cluster size for both the first hydrogen bond to the most acidic proton and the average hydrogen bond.

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Title: Cooperativity in ionic liquids
Creators: Simone Kossmann - Institut für Physikalische und Theoretische Chemie, Universität Bonn, Wegelerstrasse 12, D-53115 Bonn, Germany
Jens Thar
Barbara Kirchner
Patricia A Hunt
Tom Welton
Publication Details: The Journal of chemical physics, Vol.124(17), pp.174506-174506-12
Academic Unit: Molecular Biosciences, School of
Publisher: United States
Identifiers: 99900548252701842
Language: English
Resource Type: Journal article