ESR-spectroscopy in ionic liquids: Dynamic linebroadening effects caused by electron-self exchange reactions within the methylviologene redox couple.
Well-resolved ESR-spectra of the methylviologene radical cation (MV*+) are recorded in room-temperature liquid ions as solvents. The temperature dependences of the ESR-coupling constants are similar to those measured in classical organic solvents. Electron-self exchange rates are reported for the methylviologene redox couple (MV++/MV*+) in 1-butyl-3-methylimidazolium hexafluorophosphate (bmim+ PF6-), 1-butlyl-3-methylimidazolium fluoroborate (bmim+ BF4-) and 1-ethyl-3-imidazolium ethylsulfate (emim+ O3SOEt-) within a temperature range of 350 K < or = T < or = 460 K. The diffusion controlled rate constants observed vary between 8.2 x 10(7) M(-1) s(-1) and 1.2 x 10(9) M(-1) s(-1). From temperature-dependent measurements the activation energies obtained range from 27.4 kJ/mol in emim+ O3SOEt- to 42.1 kJ/mol in bmim+ PF6-, respectively.
Grampp
Günter
G
Institute of Physical and Theoretical Chemistry, Graz University of Technology, Technikerstrasse 4/I, A-8010 Graz, Austria. grampp@ptc.tugraz.at
Kattnig
Daniel
D
Mladenova
Boryana
B
D001881:Borates / Q000737:chemistry*; D004058:Diffusion; D004578:Electron Spin Resonance Spectroscopy; D004583:Electrons; D007093:Imidazoles / Q000737:chemistry*; D010084:Oxidation-Reduction; D010269:Paraquat / Q000737:chemistry*; D012996:Solutions / Q000737:chemistry
C419324:1-butyl-3-methylimidazolium tetrafluoroborate; D001881:Borates; D007093:Imidazoles; D012996:Solutions; D010269:Paraquat