Electron transfer (ET) kinetic rate constants k s in Ethaline (1:2 Choline Chloride + Ethylene Glycol) have been measured for two common redox couples (ferrocene/ferrocenium and ferrocyanide/ferricyanide) on a glassy carbon electrode and compared with ET kinetics in ionic liquids and classical organic solvents in the same conditions (acetonitrile and water). A particular care has been taken to treat ohmic drop in DES. For both couples, we found that ET rate constants are just a little lower than those measured in classical solvents (around 50% or less). These results contrast with ET rates in ionic liquids where electron transfers are considerably slower (100 times lower). Data are discussed as function of the solvent relaxation time using Marcus Theory for an adiabatic electron transfer.

A new side‐chain ferrocene (Fc)‐containing polyelectrolyte has been synthesized by controlled ring‐opening metathesis polymerization of a water‐soluble Fc‐containing norbornene‐based quaternary ammonium salt, as well as the corresponding covalently cross‐linked polyelectrolyte hydrogel. In order to provide Fc‐containing supramolecular polyelectrolyte hydrogels whose swelling property is largely improved by host−guest interaction, a covalently cross‐linked polyelectrolyte hydrogel is soaked into the β‐CD aqueous solution to form β‐CD@Fc supramolecular polyelectrolyte hydrogel, or alternatively the quaternary ammonium salt supramolecular monomer is first formed, then copolymerized with a crosslinking agent to fabricate the supramolecular hydrogel with better water absorption ability. All the Fc‐containing hydrogels exhibited good redox‐responsiveness with swelling–shrinking behaviors by chemically reversibly adjusting the disassembly/assembly of β‐CD@Fc inclusion complexes. This is the first example of side‐chain Fc‐containing polycationic supramolecular hydrogels possessing swelling–shrinking properties based on the splitting/combining of β‐CD and Fc units, and potential applications are expected as controlled drug delivery and actuators.

The electrochemical reduction of a series of substituted benzoquinone have been examined in ethaline chosen as an example of ionic deep eutectic solvent. Experiments show the importance of hydrogen-bonding interactions between the quinone intermediates and the solvent. The effects are notably visible on the values of reduction potentials that much more positive in ethaline than in a molecular solvent like acetonitrile and the small difference between the first and second reduction potentials. The amplitude of the stabilization increases with the donor character of the substituent. Concerning the second reduction, the peak currents are considerably smaller than those of the first reduction and almost disappear at high scan rates (above 50 V s -1 ). This behavior could be explained considering a chemical step prior to the electron transfer that becomes the limiting step (CE mechanism). As a remarkable feature, the electron transfer kinetics remain fast despite the hydrogen-bonding interactions (ks = 0.12 -0.14 cm s -1 ).