Electrochemistry and photoelectrochemistry of phenothiazine dye-β-cyclodextrin inclusion complexes

Abstract

The electrochemistry and photoelectrochemistry of inclusion complexes of phenothiazine dyes with β- cyclodextrin (CD) have been studied. The electrochemical behaviour of phenothiazine dye inclusion complexes show that the CD complexation de-aggregates the dimer dye molecule into a monomer dye molecule. The diffusion coefficients calculated from the cyclic voltammetric data were found to increase with increasing CD concentration up to a molar ratio [CD]/[dye] = 2.0 ± 0.3. A further increase of CD concentration was found to decrease the diffusion coefficients. These observations show the formation of 1:1 and 1:2 dye-CD inclusion complexes. A two-fold increase in photogalvanic output for the dye - Fe²⁺ photoredox system was observed upon addition of CD to the dye solution. This is due to the de-aggregation of the photoinactive dimer dye into a photoactive monomer dye. The application of photoelectrochemical techniques to the study of CD complexation is reported.