Electrospray Mass Spectral Fragmentation Study of N,N′-Disubstituted Imidazolium Ionic Liquids

The tandem positive electrospray mass spectrometry (ESMSn) fragmentation of ionic liquids incorporating the 1-methyl-imidazolium ring substituted on NII with an alkyl chain functionalized with an alcohol, carboxylic acid, or an iodobenzyl or iodobenzoyl ester is presented for the first time. The influence of chain length and function is studied. Esterified structures led to intense CID fragments lacking the imidazolium ring allowing full characterization of the ester moiety. Fragment ion compositions for this interesting and newly important class of compounds are established through accurate mass data and deuterium labeling. The presence of the cationic ring system produces intense even electron molecular cations in electrospray that undergo multiple stages of CID to yield fragments which often are radical cations. Unusual losses of methyl and hydrogen radicals are frequently noted.