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

Abstract

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(BF 4) 0.75] n grow over platinum, gold and glassy carbon surfaces. Solutions of Nitmdbtaa and pyrrole in CH 2Cl 2, upon chemical oxidation, show an unusual behaviour of the absorbance measured at λ max = 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.