Adsorption Behavior of N-Containing Heterocycles at a Mercury/Water Interface

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Abstract
Adsorption behavior of 1-methylimidazole and 1-methylbenzimidazole at a mercury/water interface were investigated by electrocapillary measurement. These heterocycles showed a horizontal orientation at lower surface excesses, but at higher surface excesses a vertical one complicated by the presence of the horizontal one. In positive surface charge density, 1-methylbenzimidazole showed an anomalous behavior in which the potential drops across the inner layer, Δ2Mφ does not change with adsorption through the displacement of the water molecules on the electrode. The analysis of the electrosorption valency indicated the absence of a partial charge transfer between the electrode and the adsorbate. This anomalous behavior was interpreted by the compensation effect between the polarization of the water molecules due to the permanent dipoles and that of the 1-methylbenzimidazole molecules due to the dipoles induced in the electric field.