The rigidity of self-assembled cofacial porphyrins influences selectivity and kinetics of oxygen reduction electrocatalysis

We report the electrocatalytic Oxygen Reduction Reaction on a rigid Co(ii) porphyrin prism scaffold bridged by Ag(i) ions. The reactivity of this scaffold differs significantly from previous prism catalysts in that its selectivity is similar to that of monomer (∼35% H₂O) yet it displays sluggish kinetics, with an order of magnitude lower k_s of ∼0.5 M⁻¹ s⁻¹. The deleterious cofacial effect is not simply due to metal-metal separation, which is similar to our most selective prism catalysts. Instead we conclude the structural rigidity is responsible for these differences.