Cyclic Voltammograms of Thin Film Cobalt Phthalocyanine Derivatives, Assignment of Each Cathodic Wave Formation of Protonated Species of Cobalt(I) Phthalocyanines

<jats:title>Abstract</jats:title><jats:p>Cyclic voltammograms(cvs) of thin films of (29H, 31H,‐phthalocyaninato‐N<jats:sup>29</jats:sup>, N<jats:sup>30</jats:sup>, N<jats:sup>31</jats:sup>, N<jats:sup>32</jats:sup>)cobalt(II): CoPc (1), CoPc(COOH)<jats:sub>4</jats:sub> (2), and monomeric CoPc(COOH)<jats:sub>8</jats:sub> (3) shown in Fig. 1 have been investigated. Cv of <jats:bold>2</jats:bold> on a glassy carbon electrode, in a N<jats:sub>2</jats:sub> saturated 1 M sulfuric acid solution, shows four cathodic waves at 0.10 V (<jats:italic>a</jats:italic>), —0.20 V (<jats:italic>b</jats:italic>), —0.48 V (<jats:italic>c</jats:italic>), and —0.73 V (<jats:italic>d</jats:italic>) vs. see. Each wave is assigned as follows; both <jats:italic>a</jats:italic> and <jats:italic>b:</jats:italic> redox of central Co(II)/α‐form of HCo(I)Pc(COOH)<jats:sub>4</jats:sub> (4), <jats:italic>c:</jats:italic> redox of <jats:bold>4</jats:bold>/H<jats:sub>2</jats:sub>Co(I)Pc(COOH)<jats:sub>4</jats:sub> (<jats:bold>6</jats:bold>), <jats:italic>d:</jats:italic> formation of H<jats:sub>3</jats:sub>Co(I)Pc(COOH)<jats:sub>4</jats:sub> (7). Incomplete air oxidation of 7 gives a film β‐form of HCoPc(COOH)<jats:sub>4</jats:sub> (5) which showed a cathodic wave at — 0.56 V vs. see (<jats:italic>d</jats:italic>) to give 7. Chemical reduction of 2 with Na<jats:sub>2</jats:sub>S was followed by cv of thin film of the reaction mixture. Protonation of the product gives semistable film of 5. These assignments are based on the visible spectra, color change and cv behavior of the thin films of 2 under polarization at various potentials. Cv of 3 shows four reversible cathodic waves corresponding to that of 2. Reversibility of the forth wave (<jats:italic>e</jats:italic>) seemed to relate strongly with the character and the number of the substituent on the macrocyclic ring.</jats:p>