Spectroscopic and electrochemical characterization of solutions and films of a new redox couple: Co(II)/Co(III) N-confused porphyrin

Co(II) ion was introduced in N-confused tetraphenylporphyrin (NCTPP) as evidenced by ESR and UV–Vis spectroscopy as well as electrochemical methods. The Co(II)NCTPP complex shows a typical ESR spectrum of a high spin 3d7 Co(II) ion, Soret bands at 460 and 445 nm in CH2Cl2 and CH3CN, respectively, and oxidation potential of +0.55 V vs. Ag/AgCl/KCl (satd.). Adsorbed films of Co(II)NCTPP on glassy carbon electrodes are stable and show reversible redox waves in aqueous basic solutions attributed to the Co(II)/Co(III)NCTPP couple with E1/2 = +0.025 V at pH 14. It is also shown that NCTPP can be electropolymerized and the films readily metallate with Co(II) ions.