ANODIC-DISSOLUTION OF METALLOPHTHALOCYANINE LAYERS AND THEIR INTRINSIC OXIDATION

Voltammetric measurements at a Pt-RRDE, where vacuumdeposited MePc-layers (70-700 nm) are present at the disc, were performed in 0.1 M LiClO4 in acetonitrile. Any dissolved MePc(z+)-species can be rereduced at the ring. Anodic dissolution was found to be the only process in the case of FePc and CoPc at relatively negative potentials. The cations dissolve layer by layer. For NiPc and CuPc, three different anodic processes can be distinguished: I) Anodic insertion of anions into the solid without any dissolution of cationic species. II) A further insertion of anions at more positive potentials, which is accompanied by a slow dissolution of the material. This is indicated by a relatively weak cathodic ring current. Lattice dynamics in the course of the anodic insertion of anions leads to a destabilization of the solid. III) A strong ring current shows the anodic dissolution of the whole MePc-layer at even more positive potentials. It is accompanied by a chemical dissolution to release the anions, which were inserted in the course of steps I and II. The consequences with respect to the long term stability of MePc are discussed.