Voltammetric study of protonated 1,10-phenanthroline cation transfer across the water/nitrobenzene interface

Abstract

The ion transfer of 1,10-phenanthroline (phen) across the water/nitrobenzene interface has been studied in the pH range 1-7 by electrochemical methods, adding phen to the aqueous phase or to the organic (nitrobenzene) phase. Current-scan polarography at an ascending water electrode and potential-scan cyclic voltammetry at a stationary plane electrode were used. With each addition, an anodic wave caused by the transfer of a protonated phen (Hphen+) from the aqueous to the organic phase was observed. Here a detailed mechanism of the ion transfer is proposed by considering branch diffusions of phen species from the interface to either bulk phase by which the Hphen+ transfer producing the anodic wave is depressed. With the addition of phen to the aqueous phase, the wave became deformed, noisy and steep, and finally separated into two waves as the phen concentration was increased and the pH was decreased. This is probably caused by the interfacial adsorption of Hphen+. The adsorption phenomenon is also discussed with the aid of electrocapillary curves. © 1992.