Synthesis, characterization and electrode adsorption studies of porphyrins coordinated to ruthenium(II) polypyridyl complexes

Two new porphyrins, meso-tris-3,4-dimethoxyphenyl-mono-(4-pyridyl)porphyrin (H2MPy3,4DMPP) and meso-tris-3-methoxy-4-hydroxyphenyl-mono-(4-pyridyl)porphyrin (H2MPy3M4HPP), and their ruthenium analogs obtained by coordination of [Ru(bpy)2Cl]+ groups (where bpy = 2,2′-bipyridine) to the pyridyl nitrogens have been synthesized and studied by electronic absorption spectroscopy, cyclic voltammetry and spectroelectrochemistry. These ruthenated porphyrins couple Ru chromophores to porphyrins containing electroactive meso-substituents. The highest energy electronic absorption for the ruthenated complexes is assigned as a bpy(π) → bpy(π*) intraligand charge transfer while the next lowest energy electronic absorption is assigned as Ru(dπ) → bpy(π*) metal-to-ligand charge transfer (MLCT) transition. The RuIII/II couples occur at approximately 0.95 V versus the SHE reference electrode in acetonitrile solutions. The first oxidation of the porphyrin is localized on the 3,4-dimethoxyphenyl and 3-methoxy-4-hydroxyphenyl substituents, respectively. Electroactive surfaces result from adsorption of these compounds onto glassy carbon electrodes followed by anodic cycling in acidic media.

Graphical abstractPorphyrins containing electrochemically active meso-substituents and ruthenium polypyridyl groups have been prepared and studied. These new complexes display rich redox and spectroscopic properties. When adsorbed onto glassy carbon electrodes and cycled anodically in acidic media the modified electrodes show interesting electrochemical properties.Figure optionsDownload full-size imageDownload as PowerPoint slide