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Towards Understanding the Solvent‐Dynamic Control of the Transport and Heterogeneous Electron‐Transfer Processes in Ionic Liquids
Author(s) -
Bhat Mohsin Ahmad,
Ingole Pravin P.,
Randriamahazaka Hyacinthe
Publication year - 2017
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201600442
Subject(s) - ionic liquid , electron transfer , solvent , ionic bonding , chemistry , chemical physics , organic chemistry , ion , catalysis
The impact of temperature‐induced changes in solvent dynamics on the diffusion coefficient and standard rate constant k 0 for heterogeneous electron transfer (ET) of ethylferrocene (EFc) in 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([BMIM][PF 6 ]) is investigated. The results are analysed to understand the impact of solvent‐dynamic control, solute–solvent interactions and solvent friction on the transport of redox probes and k 0 . Concentration dependence of the diffusion coefficient of EFc in [BMIM][PF 6 ] is observed. This is attributed to the solute‐induced enhancement of the structural organisation of the ionic liquid (IL), which is supported by the concentration‐dependent UV/Vis absorption and photoluminescence responses of EFc/[BMIM][PF 6 ] solutions. Similar values of the activation energies for mass transport and ET and a linear relationship between the diffusion coefficient and the heterogeneous ET rate is observed. The ratio between the diffusion coefficient and the heterogeneous rate constant allows a characteristic length L d , which is temperature‐independent, to be introduced. The presented results clearly establish that mass transport and heterogeneous ET of redox probes are strongly correlated in ILs. It is proposed that the apparent kinetics of heterogeneous ET reactions in ILs can be explained in terms of their impact on thermal equilibration, energy dissipation and thermal excitation of redox‐active probes.