Evidence for laser-induced formation of solvated electrons in room temperature ionic liquids

The photolytic generation of solvated electrons was observed for the first time in two room temperature ionic liquids (RTILs), trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide (IL) and 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethylsulfonyl)imide (IL). A 70 fs UV-pulse was used to...

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Bibliographic Details
Published in:Physical chemistry chemical physics : PCCP 2006-01, Vol.8 (27), p.3192-3196
Main Authors: Chandrasekhar, N, Endres, F, Unterreiner, A-N
Format: Article
Language:English
Subjects:
Absorption
Computer Simulation
Electrons
Free Radical Scavengers - chemistry
Imides - chemistry
Ions - chemistry
Lasers
Models, Chemical
Photochemistry
Photolysis
Piperidines - chemistry
Pyrrolidines - chemistry
Spectrophotometry, Ultraviolet
Temperature
Ultraviolet Rays
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Summary:The photolytic generation of solvated electrons was observed for the first time in two room temperature ionic liquids (RTILs), trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide (IL) and 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethylsulfonyl)imide (IL). A 70 fs UV-pulse was used to excite the RTILs, while the transient response was monitored in the visible and near-infrared spectral regions. Immediately after excitation, a pulse duration limited rise of the induced absorption indicated the formation of solvated electrons suggesting the existence of pre-formed traps in RTILs. A broad transient absorption spectrum with a full width at half maximum of about 0.9 eV, typical for solvated electrons, was reconstructed from the transient profiles. Wavelength-independent relaxation dynamics at longer delay times suggest a lifetime of solvated electrons in the ns regime in agreement with results from pulse radiolysis studies. Adding 1,1-dimethylpyrrolidinium iodide to IL led to an increase of the UV absorbance and consequently, to an increase of the yield of solvated electrons. Furthermore, this solute is an efficient electron scavenger causing the transients to decay within about 40 ps.
ISSN:1463-9076
1463-9084
DOI:10.1039/b606234b