Symmetrical and unsymmetrical quadruply aza-bridged closely interspaced cofacial bis(5,10,15,20-tetraphenylporphyrins). 4. Structure and conformational effects on electrochemistry and the catalysis of electrochemical reduction of dioxygen by doubly, triply, and quadruply N,N-dimethylene sulfonamide bridged dimer bis(cobalt tetraphenylporphyrins)