Issue 15, 2012

Zwitterionic clusters with dianion core produced by electrospray ionisation of Brønsted acidic ionic liquids

Abstract

New Brønsted acidic ionic liquids (BAILs) are prepared by treating zwitterions, which are composed of an imidazolium cation and a sulfonate anion, with an alkanedisulfonic acid. Acidification of the zwitterions produces the cation and deprotonation of the alkanedisulfonic acid forms the anion of the new BAILs. Direct laser desorption/ionisation (LDI), matrix-assisted LDI (MALDI) and electrospray ionisation (ESI) are employed to transfer ions into the gas-phase for detection by mass spectrometry and for dissociation studies by tandem mass spectrometry. The components of the BAILs are confirmed by LDI and MALDI by the detection of the respective cation and anion and by ESI by the observation of the cation and the dianion. A prominent feature of ESI is the formation of aggregates (cluster ions). Positively charged cluster ions are formally composed of multiple zwitterions plus one additional proton. In the negative-ion mode the clusters also incorporate the zwitterions which are, however, linked with the alkanedisulfonate dianion. In collision-induced dissociations (CID), the cationic aggregates show the evaporation of zwitterions until the protonated zwitterion is reached. Similarly, the cluster dianions release zwitterions until the free alkane disulfonate dianion is reached. However, the 1 : 1 adduct of dianion and zwitterion also displays proton transfer and Coulomb explosion into the mono-protonated disulfonic mono-anion and an imidazole-based carbene with sulfonate mono-anion.

Graphical abstract: Zwitterionic clusters with dianion core produced by electrospray ionisation of Brønsted acidic ionic liquids

Article information

Article type
Paper
Submitted
21 Dec 2011
Accepted
05 Mar 2012
First published
14 Mar 2012

Phys. Chem. Chem. Phys., 2012,14, 5115-5121

Zwitterionic clusters with dianion core produced by electrospray ionisation of Brønsted acidic ionic liquids

J. Li, W. Wei, L. C. Nye, P. S. Schulz, P. Wasserscheid, I. Ivanović-Burmazović and T. Drewello, Phys. Chem. Chem. Phys., 2012, 14, 5115 DOI: 10.1039/C2CP24071H

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