Spectroscopic and electrochemical studies of high-valent water soluble manganese porphyrine. Electrocatalytic water oxidation.

ALEJANDRA LUNA, FERNANDO MOYANO, LEONIDES SERENO, FABIANA D'ERAMO

ELECTROCHIMICA ACTA

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2014 vol. 135 p. 301 - 310

0013-4686

Abstract This paper reports the intermediate species of water-soluble 5,10,15,20- tetra(N-methylpyridyl) porphyrinato manganese (III) chloride,[PMn(III)]Cl5,obtained by homogeneous chemical oxidation and electrochemical oxidation in aqueous media. In order to understand some of the electrochemical processes,studies focused on UV-vis and cyclic voltammetry techniques. Firstly,[PMn(III)]Cl5 was characterized by spectroscopy in pH 7 and 10, measuring the changes produced by oxidation with a chemical agent. These studies showed that intermediates with higher oxidation states, [PMn(IV)=O]Cl4 and [PMn(V)=O]Cl5, are formed under these conditions and they are more stable at pH 10 at room temperature. The same result was obtained by electrochemical oxidation. The electrochemical studies showed that [PMn(III)]Cl5 is adsorbed on glassy carbon electrode surface. However, this does not help explain the high oxidation current obtained in both pHs at high anodic potentials. The experimental results obtained indicate that the chloride ion present in the porphyrin structure and the water of the reaction medium are active species responsible for the observed catalytic current at high potentials.