Reversible Reduction and Reoxidation of Entire Thin Films of Octacyanophthalocyanine

The electrochemical properties of solid films of Mt‐2,3,9,10,16,17,23,24‐octacyanophthalocyanine 2 were studied by cyclic voltammetry in aqueous electrolytes. The thin (10–100 nm) film electrodes show remarkably stable electrochromic redox behavior, and the charge exchanged in the cathodic and anodic waves, respectively, was found to be between 2 and 3 F/mol for scan rates up to 400 mV/s. For charge compensation, the intercalation of cations is required. At low pH values (intercalation of protons), nernstian behavior was observed, while in alkaline solutions the intercalation of the cations Li+, Na+, or K+ into the solid film was found to be the rate‐determining step. From the half‐width of the current waves, the number of electrons involved in the overall reaction was inferred and found to be different in acid and alkaline solutions. Compared to unsubstituted phthalocyanines 1, the characteristic qualities of the electrodes are associated with the high electric conductivity of 2 and the electron accepting properties of the substituents of the ligand.