Electroactive polymeric material with condensed structure on the basis of magnesium(II) polyporphine
Résumé
Previous publication of the authors presented evidences that electroch emical oxidation of Mg(II) porphine (fully unsubstituted porphyrin, MgP) in acetonitrile (AN) at a very low potential leads to deposition of films at electrode surface corresponding to typical electroactive polymers, with their reversible transition betwee n the electronconducting and insulating states depending on the electrode potential/oxidation level ("film of type I"). It is demonstrated in the actual publication that these films in contact with a monomer-free solution are subject to an irreversible transformation to quite a different material ("film of type II") under the influence of a higher positive potential (above 0.5-0.6 V vs. Ag/Ag + in AN). Films with the same properties may also be obtained directly by electrooxidation of the monomer, MgP, at a sufficiently high potential. Films of type II possess a high redox activity and electronic conductivity within the whole potential interval of above 3 V in the width. Their grayish color is related to a constant absorption intensity within the whole range of wavelengths studied (320-1000 nm). On the basis of a combination of experimental observations (ATR IR ad XPS) and literature data the molecular structure of this new material is assumed to be polymer chains of directly linked porphine units (with a par tial loss of Mg cations), probably with multiple bonds (meso-meso and β-β type) between the neighboring units.
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