Oxygen reduction at negatively charged iron porphyrins heat-treated and bridged by alkaline-earth metal ions

Abstract

An ordered network of tetrasodium tetra(4-sulphonatophenyl)porphyrin iron(III) chloride (FeTPPS 4 Na 4 ), which exhibited a higher catalytic activity for oxygen reduction than Co and Ir(CO)TPPS 4 Na 4 , was fabricated by complexation with alkaline-earth metal ions. Heat treatment of these complexes enhanced their catalytic activity with the 2 highest performance observed with Ba 2+ -FeTPPS 4 . The onset potential for oxygen reduction (E onset ) was 720 mV vs. Ag|AgCl, which is almost the same as that for Pt-impregnated carbon black. The number of electrons, n, transferred during oxygen reduction at a Ba 2+ -FeTPPS 4 -coated electrode, as determined by rotating ring-disc experiments, was 3.9 and suggests that oxygen was reduced to water. A neutral solution of FeTPPS 4 Na 4 was acidified by the addition of barium ion, and the elemental ratio

Energy-Related Small Molecule Activation Reactions: Oxygen Reduction and Hydrogen and Oxygen Evolution Reactions Catalyzed by Porphyrin- and Corrole-Based Systems

“…Other Fe porphyrins studied as ORR catalysts include Fe III octaethylporphyrin chloride 45 (Figure ) and Fe III tetra­(4-sulfonatophenyl)­porphyrin chloride 46 (Figure ). Similar to the results reported by Costentin, Dridi, and Savéant, the adsorption of 45 on a GC electrode caused a positive shift of the Fe III /Fe II redox potential, indicating a stronger interaction between the Fe II form of 45 in the adsorbed state and the electrode surface. The coordination responsible for this effect could involve the back bonding of Fe II to unsaturated surface ligands (i.e., carbonyl-like groups).…”

Highly Sensitive Cobalt Porphyrin Biomimetic Catalyzed Flow Injection Chemiluminescence Determination of Diethylstilbestrol in Pharmaceuticals

“…Metalloporphyrin complexes are important 18 π-conjugated organic molecules and have been extensively used in a variety of chemical, biological and clinical studies to mimic the active sites of enzymes 12 . Metalloporphyrin complexes have been widely used as a substitute for enzymes in several chemiluminescence systems for analysis applications, but most are based on totally synthetic metallo-tetraarylporphyrins (MTPPs) or naturally occurred metalloporphyrins 13,14 .…”