2 research outputs found
Temperature and Pressure Dependence of the Electrical Conductivity of 1‑Butyl-3-methylimidazolium Bis(trifluoromethanesulfonyl)amide
The
electrical conductivities of the ionic liquid 1-butyl-3-methylimidazolium
bisÂ(trifluoroÂmethanesulfonyl)Âamide ([BMIM]Â[Tf<sub>2</sub>N]) have been determined between (273 and 353) K over an extended
pressure range up to 250 MPa by both electrochemical impedance spectroscopy
and conductance bridge techniques. The results obtained by the two
techniques are generally in good agreement, within 3%, though the
conductance bridge results yield lower values outside the experimental
uncertainties at higher conductivities, that is, at higher temperature
and lower pressures where the maximum deviation is −7%. The
temperature and pressure dependence of both the conductivity and molar
conductivity have been represented by modified Vogel–Fulcher–Tammann
equations. The molar conductivity scales with the viscosity, with
overlapping isobars and isotherms, so that a Walden plot, the logarithmic
projection of molar conductivity versus fluidity (reciprocal viscosity),
is a straight line with a similar slope (0.924) to those obtained
for other 1,3-dialkylimidazolium ionic liquids
Excited-State Proton Transfer of Cyanonaphthols in Protic Ionic Liquids: Appearance of a New Fluorescent Species
Excited-state proton
transfer (ESPT) of 5-cyano-2-naphthol (5CN2)
and 5,8-dicyano-2-naphthol (DCN2) in three different protic ionic
liquids (PILs), triethylammonium trifluoromethanesulfonate ([N<sub>222</sub>H]Â[CF<sub>3</sub>SO<sub>3</sub>]), triethylammonium methanesulfonate
([N<sub>222</sub>H]Â[CH<sub>3</sub>SO<sub>3</sub>]), and triethylammonium
trifluoroacetate ([N<sub>222</sub>H]Â[CF<sub>3</sub>COO]), was studied
by time-resolved fluorescence. In [N<sub>222</sub>H]Â[CF<sub>3</sub>SO<sub>3</sub>], both 5CN2 and DCN2 showed fluorescence only from
ROH* (normal form of substituted naphthol in the excited states),
indicating that no ESPT occurred in [N<sub>222</sub>H]Â[CF<sub>3</sub>SO<sub>3</sub>]. For 5CN2 in [N<sub>222</sub>H]Â[CH<sub>3</sub>SO<sub>3</sub>], fluorescence bands from ROH* and RO<sup>–</sup>*
(anionic form of substituted naphthol in the excited states) were
observed, indicating that 5CN2 could dissociate proton to surrounding
solvents and form RO<sup>–</sup>*. More interestingly, 5CN2
in [N<sub>222</sub>H]Â[CF<sub>3</sub>COO] and DCN2 in [N<sub>222</sub>H]Â[CH<sub>3</sub>SO<sub>3</sub>] and [N<sub>222</sub>H]Â[CF<sub>3</sub>COO] showed an anomalous fluorescence band around 470 nm (5CN2) or
around 520 nm (DCN2) which has not been reported previously. The kinetics
of each fluorescent component of 5CN2 and DCN2 was analyzed on the
basis of the time profile of fluorescence intensity. Plausible ESPT
schemes of 5CN2 and DCN2 were discussed on the basis of the kinetics
and the basicity of anion in PILs