TY - JOUR
T1 - Ultraviolet photoionization efficiency of the vaporized ionic liquid 1-butyl-3-methylimidazolium tricyanomethanide
T2 - Direct detection of the intact ion pair
AU - Chambreau, Steven D.
AU - Vaghjiani, Ghanshyam L.
AU - Koh, Christine J.
AU - Golan, Amir
AU - Leone, Stephen R.
PY - 2012/10/4
Y1 - 2012/10/4
N2 - We present the first direct measurement of a neutral, intact ion pair photoionization efficiency (PIE) curve for a vaporized ionic liquid, 1-butyl-3-methylimidazolium tricyanomethanide, using tunable vacuum ultraviolet (VUV) photoionization time-of-flight mass spectrometry (PI-TOFMS). The ionization potential (IP) for the ion pair is experimentally determined to be 6.6 ± 0.5 eV, which matches reasonably well with the adiabatic IP of 7.3 ± 0.2 eV calculated at the M06/6-31+G(d,p) level of theory. The lifetime to dissociation of the cation-radical complex formed upon ionization of the ion pair is highly dependent upon entropic contributions. Thermal gravimetric analyses (TGA) determined the enthalpy of vaporization to be ΔH vap(298 K) = 143.5 ± 6.2 kJ/mol and that vaporization of BMIM +TCM - as ion pairs is the dominant mechanism for mass loss under the experimental conditions for VUV PI-TOFMS (T = 433 K).
AB - We present the first direct measurement of a neutral, intact ion pair photoionization efficiency (PIE) curve for a vaporized ionic liquid, 1-butyl-3-methylimidazolium tricyanomethanide, using tunable vacuum ultraviolet (VUV) photoionization time-of-flight mass spectrometry (PI-TOFMS). The ionization potential (IP) for the ion pair is experimentally determined to be 6.6 ± 0.5 eV, which matches reasonably well with the adiabatic IP of 7.3 ± 0.2 eV calculated at the M06/6-31+G(d,p) level of theory. The lifetime to dissociation of the cation-radical complex formed upon ionization of the ion pair is highly dependent upon entropic contributions. Thermal gravimetric analyses (TGA) determined the enthalpy of vaporization to be ΔH vap(298 K) = 143.5 ± 6.2 kJ/mol and that vaporization of BMIM +TCM - as ion pairs is the dominant mechanism for mass loss under the experimental conditions for VUV PI-TOFMS (T = 433 K).
UR - http://www.scopus.com/inward/record.url?scp=84867167216&partnerID=8YFLogxK
U2 - 10.1021/jz301242w
DO - 10.1021/jz301242w
M3 - Article
AN - SCOPUS:84867167216
SN - 1948-7185
VL - 3
SP - 2910
EP - 2914
JO - Journal of Physical Chemistry Letters
JF - Journal of Physical Chemistry Letters
IS - 19
ER -