The evaporation study of silicon-containing ionic liquid

Evaporation Study of an Ionic Liquid with a Double-Charged Cation

“…The MALDI mass spectra (positive and negative ion modes) of three [C 3 (MIm) 2 2+ ]­[Tf 2 N – ] 2 samples (Figures and ) demonstrated the molecular ions, i.e., {[C 3 (MIm) 2 2+ ]­[Tf 2 N – ]­[Tf 2 N • ]} •+ and {[C 3 (MIm) 2 •+ ]­[Tf 2 N – ] 2 } •– , to be completely absent. Such a behavior is quite typical for an IL in MALDI mass spectra. − The spectra of the starting sample and residue in the cell practically coincided. In both cases, the peaks of the {[C 3 (MIm) 2 2+ ][Tf 2 N – ]} + charged cluster and [Tf 2 N – ] parent anion predominated in positive and negative ion spectra, respectively.…”

“…The vapor of the IL was found to be composed of relatively weakly bound ionic molecules, − which are sometimes named ion pairs (ion triplets in the case of dicationic ILs , ). In mass spectra (various ionization techniques), they usually give fragmented [Cat + ] and [An – ] ions as main peaks in the positive and negative ion modes, respectively. ,,,,− The molecular ions have been managed to be detected only in field ionization mass spectra of 1-ethyl-3-methylimidazolium thiocyanate ([C 2 MIM + ]­[SCN – ]), 1-butyl-3-methylimidazolium tricyanomethide ([C 4 MIM + ]­[C­(CN) 3 – ]), N -butyl-3-methylpyridinium dicyanimide ([C 4 MPy + ]­[N­(CN) 2 – ]), and 1-butyl-1-methylpyrrolidinium bis­(trifluoromethanesulfonyl)­amide ([C 4 MPyrr + ]­[Tf 2 N – ]) . Ions, retaining both cationic and anionic portions, have been also observed in the electron impact ionization (EI) mass spectrum of the silicon-containing IL 1,2-dimethyl-3-(1′,1′,3′,3′-tetramethyl-3′-phenyldisiloxanyl)­methylimidazolium bis­(trifluoromethanesulfonyl)­amide ([PhC 5 OSi 2 MMIm + ]­[Tf 2 N – ]) .…”

“…In mass spectra (various ionization techniques), they usually give fragmented [Cat + ] and [An – ] ions as main peaks in the positive and negative ion modes, respectively. ,,,,− The molecular ions have been managed to be detected only in field ionization mass spectra of 1-ethyl-3-methylimidazolium thiocyanate ([C 2 MIM + ]­[SCN – ]), 1-butyl-3-methylimidazolium tricyanomethide ([C 4 MIM + ]­[C­(CN) 3 – ]), N -butyl-3-methylpyridinium dicyanimide ([C 4 MPy + ]­[N­(CN) 2 – ]), and 1-butyl-1-methylpyrrolidinium bis­(trifluoromethanesulfonyl)­amide ([C 4 MPyrr + ]­[Tf 2 N – ]) . Ions, retaining both cationic and anionic portions, have been also observed in the electron impact ionization (EI) mass spectrum of the silicon-containing IL 1,2-dimethyl-3-(1′,1′,3′,3′-tetramethyl-3′-phenyldisiloxanyl)­methylimidazolium bis­(trifluoromethanesulfonyl)­amide ([PhC 5 OSi 2 MMIm + ]­[Tf 2 N – ]) . Cluster ions, like {[Cat + ] 2 [An – ]} + and {[Cat + ]­[An – ] 2 } − , were observed in matrix-assisted laser desorption/ionization (MALDI) mass spectra. , Concerning dicationic ILs, they have been mentioned to show a double-charged parent ion [Cat 2+ ] and a single-charged cluster {[Cat 2+ ]­[An – ]} + as main peaks in the EI mass spectrum.…”

“…Most experimental work on the evaporation of ILs is focused on monocationic species. Nowadays, the vaporization enthalpy and saturated vapor pressures have been established for substituted imidazolium bis­(trifluoromethanesulfonyl)­amides, ,,,,− including those with organosilicon substituents, and also for 1-butyl-3-methylimidazolium hexafluorophosphate . Evaporation of the latter was accompanied by a partial thermal decomposition, yielding ethylimidazole as the abundant volatile product.…”

Properties of Dicationic Disiloxane Ionic Liquids

“…One of the specific properties of ionic liquids is their low volatility due to Coulomb interactions between the ions. The classical method for estimating the volatility of ionic liquids is to determine their evaporation enthalpy by various physical and chemical methods: Knudsen effusion mass spectrometry [33][34][35][36][37] or calorimetry [38]. Recently, there have been a significant number of studies where the volatility of ILs was evaluated by thermogravimetry [39][40][41].…”