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From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding
Published on: March 24, 2018
Fast substitution reactions of Pt(II) in different ionic liquids. reactivity control by anionic components
Peter Illner1, Svetlana Begel, Simon Kern
1Inorganic Chemistry, Department of Chemistry and Pharmacy, University of Erlangen-Nurnberg, Egerlandstrasse 1, 91058 Erlangen, Germany.
Abstract:
The effect of several imidazolium-based ionic liquids on the rate and mechanism of the substitution reaction of [Pt(terpyridine)Cl](+) with thiocyanate was investigated as a function of thiocyanate concentration and temperature under pseudo-first-order conditions using stopped-flow and other kinetic techniques. The obtained rate constants and activation parameters showed good agreement with the ion-pair stabilization energies between the anions of the ionic liquids and the cationic Pt(II) complex derived from density-functional theory calculations (RB3LYP/LANL2DZp) and with parameters derived from the linear solvation energy relationship set by the Kamlet-Taft beta parameter, which is a measure of a solvent's hydrogen bonding acceptor ability. In general, the substitution reactions followed an associative mechanism as found for conventional solvents, but the observed rate constants showed a significant dependence on the nature of the anionic component of the ionic liquid used as solvent. The second order rate constant measured in [emim][NTf(2)] is 2000 times higher than the one measured in [emim][EtOSO(3)]. This difference is much larger than observed for a neutral entering nucleophile studied before.
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