Modified Electrodes Using Mixed Langmuir−Blodgett Films Containing a Ruthenium Complex: Features of the Monolayers at Air−Liquid Interface

Abstract

Mixed Langmuir−Blodgett (LB) films of arachidic acid (AA) and [Ru(L)(totpy)(OH2)](ClO4)2 (L = Ph2AsCH2CH2AsPh2; 4-totpy = 4‘-(4-tolyl-2,2‘:6‘,2‘ ‘-terpyridine)) complex (2:1) were used in the preparation of modified electrodes. The incorporation of the metallic complex into mixed monolayers is noticed from the surface pressure (π−A) and surface potential (ΔV−A) isotherms. The π−A curves show a phase transition region between the expanded and condensed liquid states (LE-LC) at 35 mN/m, which is not present in the π−A curves for pure AA monolayers. In the ΔV−A isotherms there is a large expansion of the critical area and the difference between the minimum and maximum surface potential (ΔΔV) increases with the concentration of the ruthenium complex in the mixed monolayer. Combining the π−A curve data with the ultraviolet−visible spectra for the corresponding LB films, the dissociation degree of the fatty acid within the mixed LB films is calculated as 0.67. The FTIR spectra confirm the partial dissociation of the acid. The cyclic voltammograms of the modified electrodes of AA/ruthenium complex (2:1) at pH = 8.1, in the presence of benzyl alcohol showed pronounced enhancement of the anodic current corresponding to the RuIV/RuIII couple. This is indicative of an electrocatalytic behavior.