Abstract
In bis(trifluoromethylsulfonyl)amide (TFSA−)–based ionic liquid, 1-ethyl-3-methylimidazolium TFSA− ([C2mim][TFSA]), the complex formation equilibria of Zn2+ ion with acetonitrile (AN) molecules have been investigated using 15N NMR spectroscopy with a help of density functional theory (DFT) calculation. Based on a comparison of the experimental 15N NMR peak of the TFSA− N atom with the calculated ones, the structure of the Zn2+ solvation complex with TFSA− anions formed in [C2mim][TFSA] has been determined. Three TFSA− anions coordinate with Zn2+ as bidentate ligands to form the monovalent complex of [Zn(tfsa)3]−. To determine the structure of the Zn2+−AN complexes formed in the [C2mim][TFSA]–AN solutions, the numbers of the experimental 15N NMR peaks of AN molecules coordinated with Zn2+ were compared with those calculated by the DFT. The complexes of [Zn(tfsa)2(an)2], [Zn(tfsa)(an)4]+, and [Zn(an)6]2+ are formed in the solutions. Their stability constants were determined from the relationship between the chemical shift value of TFSA− anions isolated from Zn2+ and the concentration ratio of AN to Zn2+.
Published Version
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