Reaction of organic and metallorganic π-cation Radicals: Electrical and electrochemical properties of polymeric materials obtained by oxidation of pyrrole and Tetraaza[14]annulenic nickel(II) complexes

The reactions between π-cation radicals generated by electrochemical or chemical oxidation of pyrrole and metallorganic complexes, i.e. tetramethyldibenzo[b,i] tetraaza[14]annulenenickel(II), Nitmdbtaa, and tetramethyldinaphtho[b,i]tetraaza[14] annulenenickel(II), Nitmdntaa, were investigated. There is voltammetric evidence that pyrrolyl units insert as organic spacers between nickel-macrocycle molecules when solutions containing controlled amounts of Nitmdbtaa and pyrrole are cycled in the range + 1.4 to −0.5 V (vs SCE). Thin conducting films of [(Nitmdbtaa)(Py)0.95(BF4)0.75]n grow over platinum, gold and glassy carbon surfaces. Solutions of Nitmdbtaa and pyrrole in CH2Cl2, upon chemical oxidation, show an unusual behaviour of the absorbance measured at λmax = 605 and 585 nm vs time. This is interpreted as due to a co-polymerization process and gives indications on the nature of the reaction intermediates. Layers of (Nitmdbtaa)n cannot be grown over polypyrrole (Ppy) by electrochemical methods. In its turn, Nitmdntaa is not found to co-polymerize with pyrrole but polymeric films of the complex can be generated on Ppy galvanostatically, by constant potential electrolysis at +1.4 V or by cycling from +1.4 to −0.5 V (vs SCE). These overlapped films show rectifying properties in the 0.0 to + 1.4 V potential range