ELECTROCHEMISTRY OF METALLOPORPHYRINS AND VIOLOGENS AT ZEOLITE Y MODIFIED ELECTRODES: EVIDENCE FOR ELECTRON TRAPPING BY MONOMOLECULAR PORPHYRIN LAYERS.

Cyclic voltammetric data are presented for electrodes coated with zeolite Y powder containing porphyrins and viologens. Half-wave potentials for viologen cations (methylviologen, benzylviologen, or N,N prime -(1,3-propenyl)-2,2 prime -bipyridinium) do not change significantly when they are exchanged into zeolite Y, whereas the reduction potentials for cobalt and zinc tetrakis (N-methyl-4-pyridyl)porphyrins shift (relative to aqueous solution) by plus 200 mV. When a viologen cation is ion exchanged into the bulk of the zeolite, and cobalt tetrakis(N-methyl-4-pyridyl)porphyrin is adsorbed onto its outer surface in monolayer quantities, current rectification and charge trapping reactions are observed.