Extrazeolite electron transfer at zeolite encapsulated polypyridyl metal complexes coated electrodes

Abstract

Polypyridyl metal complexes ([Ru(bpy)₃]²⁺ and [Fe(bpy)₃]²⁺) were synthesized inside the supercages of zeolite-Y and adsorbed on the surface of zeolite-Y (represented as Ru(II)-Y(_c/s) and Fe(II)-Y(_c/s), where "c" refers the supercage of zeolite-Y and "s" refers the surface of zeolite-Y). These zeolite-encapsulated metal complexes were coated on a platinum electrode, and their electrochemical properties were studied in 0.1 M Na₂SO₄ and in 0.05 M H₂SO₄. The Ru(II)-Y_(c) and Fe(II)-Y_(c) were electroinactive in 0.1 M Na₂SO₄. The same metal complexes in zeolite show electrochemical activity in the presence of H+ ions. The electroinactivity of Ru(II)-Y_(c) and Fe(II)-Y_(c) complexes in 0.1 M Na₂SO₄ shows that the intrazeolite electron transfer is not occurring. The disintegration of zeolite-Y in the presence of H⁺ ions leads to the random distribution of the polypyridyl metal complexes and shows that extrazeolite electron-transfer mechanism is operating as in the case of zeolite surface adsorbed metal complexes.