Electrocatalysis on tetraruthenated nickel and cobalt porphyrins electrostatic assembled films

The meta and para-pyridine substituted isomers of nickel and cobalt meso-pyridylporphyrins coordinated to four [Ru(bpy)2Cl]+ complexes, M(TRPyP), have been obtained and fully investigated by means of electrochemistry and spectroelectrochemistry. These compounds form stable layer-by-layer electrostatic assembled films with tetrasulfonated phthalocyaninate cuprate(II) anion, exhibiting distinct electrocatalytic activity for sulfite and nitrite oxidation and reduction reactions. Interestingly, M(3-TRPyP)/CuTSPc films showed good electrocatalytic activity for the oxidation and reduction of sulfite and nitrite at pH 4.7, while at pH 6.8 both M(TRPyP) derivatives were active only for the oxidation process. Such differences were attributed to electronic structure of MTRPyPs and changes in the active site environment caused by the distinct structure and packing properties of the meta- and para-isomers, rather than to differences in the redox potentials. Summarizing, supramolecular electrocatalytic activity was demonstrated for those electrostatic assembled films introducing a new paradigm for the development of chemical sensors for simultaneous analysis of multiple substrates.