CHEN, Jingyuan

OPALLO, Marcin

SATOH, Masanori

SHUL, Galyna

Community Repository of Fukui

 ELECTROGENERATED ION TRANSFER ACROSS TOLUENE+IONIC 
LIQUID MIXTURE / AQUEOUS SOLUTION INTERFACE 
 
Galyna Shula, Masanori Satohb, Jingyuan Chenb, Marcin Opalloa 
a Institute of Physical Chemistry, Polish Academy of Sciences, Warszawa, Poland,  
b Department of Applied Physics, University of Fukui, Fukui, Japan 
Email: mopallo@ichf.edu.pl 
 
Introduction 
The electrochemical studies of ion transfer across ionic liquid / aqueous solution 
interface received some attention recently. This is because of its importance in 
extraction/separation processes [1] and established role of ionic liquids as electrochemical 
solvents [2,3]. Ion transfer processes across ionic liquid/water have been earlier studied by 
applying potential difference across liquid / liquid interface (see [4] and refs. therein). The 
generation of electric charge by electrochemical redox reaction within ionic liquid drop 
deposited on the electrode immersed in the aqueous solution represents alternative approach 
[5]. Here, this method was used to study ion transfer across toluene+ionic liquid/aqueous 
solution interface. The addition of toluene to ionic liquid allows for dissolution of large 
variety of hydrophobic metal complexes used as redox probes and substantially decreases 
viscosity of organic phase. On the other hand the addition of ionic liquid as electrolyte to 
nonpolar solvent [6] extends the range of media to study electrochemical ion transfer 
reactivity of porphyrinato metal complexes restricted to strongly coordinating solvents [7]. 
 
Results and discussion 
In the present study we use mixture of toluene and phosphonium–phosphate ionic 
liquid as organic phase and aqueous solution of salts composed of large variety of cations and 
anions. As redox probes we used ferrocene, its more hydrophobic derivatives: butyloferrocenes 
and decamethyloferrocene and Mn, Co and Fe porphyrinato complexes. The droplets of redox 
probe solution in studied mixture (and whenever possible in its pure components) were 
deposited on edge plane pyrolytic graphite electrode. After its immersion into aqueous solution 
their electrochemical behaviour was studied by cyclic voltammetry and differential pulse 
voltammetry. In most cases the dependence of redox potential on the aqueous electrolyte was 
observed. The magnitude of this effect depends also on hydrophobic properties of the redox 
probe. For more hydrophobic redox probes the correlation between redox potential and 
hydrophobic/hydrophilic properties of anion indicates anion insertion process following 
electrochemical generation of charge in organic phase. In the case of t-butyloferrocene as a 
redox probe the possible electrochemical signature of both anion insertion to and cation 
ejection from the organic phase at different potentials is observed. 
 
References 
[1] M. Koel, Crit. Rev. Anal. Chem. 35 (2005) 177. 
[2] M.C. Buzzeo, R.G. Evans, R.G. Compton, Chem. Phys. Chem. 5 (2004) 1106. 
[3] J. Zhang, A.M. Bond, Analyst 130 (2005) 1132. 
[4] N. Nishi, S. Imakura, T. Kakiuchi, Anal. Chem. 78 (2006) 2726. 
[5] J. Niedziolka, E. Rozniecka, J. Stafiej, J. Siriex-Plenet, L. Gaillon, D. Di Caprio, M. Opallo, Chem. 
Commun. (2005) 2954. 
[6] N.W. Duffy, A.M. Bond, Electrochem. Commun. 8 (2006) 892 
[7] M.J. Bonne, C. Reynolds, S. Yates, G. Shul, J. Niedziolka, M. Opallo, F. Marken, New J. Chem. 30 (2006) 
327. 


ELECTROGENERATED ION TRANSFER ACROSS TOLUENE+IONIC LIQUID MIXTURE / AQUEOUS SOLUTION INTERFACE

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