Gas-phase dissociation of ionic liquid aggregates studied by electrospray ionisation mass spectrometry and energy-variable collision induced dissociation

✍ Scribed by Ana M. Fernandes; João A. P. Coutinho; Isabel M. Marrucho

• Publisher: John Wiley and Sons
• Year: 2009
• Tongue: English
• Weight: 277 KB
• Volume: 44
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/jms.1484

✦ Synopsis

Abstract

Positive singly charged ionic liquid aggregates [(C~n~mim)~m+1~(BF~4~)~m~]^+^ (mim = 3‐methylimidazolium; n = 2, 4, 8 and 10) and [(C~4~mim)~m+1~(A)~m~]^+^ (A = Cl^−^, BF~4~^−^, PF~6~^−^, CF~3~SO~3~^−^ and (CF~3~SO~2~)~2~N^−^) were investigated by electrospray ionisation mass spectrometry and energy‐variable collision induced dissociation. The electrospray ionisation mass spectra (ESI‐MS) showed the formation of an aggregate with extra stability for m = 4 for all the ionic liquids with the exception of [C~4~mim][CF~3~SO~3~]. ESI‐MS‐MS and breakdown curves of aggregate ions showed that their dissociation occurred by loss of neutral species ([C~n~mim][A])~a~ with a ≥ 1. Variable‐energy collision induced dissociation of each aggregate from m = 1 to m = 8 for all the ionic liquids studied enabled the determination of E~cm, 1/2~ values, whose variation with m showed that the monomers were always kinetically much more stable than the larger aggregates, independently of the nature of cation and anion. The centre‐of‐mass energy values correlate well with literature data on ionic volumes and interaction and hydrogen bond energies. Copyright © 2008 John Wiley & Sons, Ltd.