A vitamin B 12 derivative, heptapropyl cobyrinate perchlorate, was readily trapped onto an indium tin oxide (ITO) electrode by a sol-gel reaction. The complex was physically retained in a silica gel film which is formed on an ITO electrode. The thickness of the film could be controlled by the withdrawing speed of the dip coating process. Formation of a sol-gel film was confirmed by SEM measurements, and the total amount of the complex in the film was determined by UV-VIS absorption spectra. The complex exhibits the Co II /Co I redox couple at Ϫ0.42 V vs. Ag-AgCl. The amount of the electroactive complex in the sol-gel film deduced from electrochemical measurements is 3.0 × 10 Ϫ11 and 6.2 × 10 Ϫ11 mol cm Ϫ2 for thicknesses of 170 and 330 nm, respectively. This electroactive complex shows a high reactivity towards organic halides, and the controlled-potential electrolysis of benzyl bromide using the sol-gel modified electrode at Ϫ1.20 V vs. Ag-AgCl in aqueous solution containing 0.1 M KCl afforded dehalogenated products, bibenzyl and toluene, with a total turnover number of >1000 for 1 h.

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Surface pressure (π)-area (A) isotherms were studied to analyze the interactions between a hydrophilic ionic liquid (IL) (ethyl(2-hydroxyethyl)dimethylammonium methanesulfonate) and a pure dipalmitoylphosphatidylcholine (DPPC) film or a DPPC-cholesterol mixed film. When the hydrophilic IL was added to an underlayer solution, the isotherm shifted toward higher areas. Intriguingly, when the hydrophilic IL was added, the packing of the film materials became loose and the elastic modulus decreased, resulting in increased flexibility. This phenomenon was most evident under a cholesterol mole fraction of 0.2. This composition resembles that of cell membranes, which typically comprise phospholipids and cholesterol, suggesting that this hydrophilic IL may be able to interact significantly with biological membranes.

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