Ligand-Bridged Heterobimetallic Polymers:  Silver(I)−Benzothiadiazole−Nickel Porphyrin Cation−Benzothiadiazole Arrays

Porphyrin {pi} cation radicals incorporating high oxidation states of Fe, Mn, Cr, and Ru catalyze epoxidations, hydroxylations, and oxidations of alkenes, alkanes, and other organic substrates. Ni(III) tetraaza complexes catalyze similar oxidations, and Ni(III) tetrapyrroles (factor 430) have been invoked in the catalytic cycle of methanogenic bacteria. Porphyrins with elegantly designed superstructures have also been synthesized in attempts to construct regiospecific catalysts that mimic the many biological processes mediated by porphyrins. The authors recently investigated a series of meso-tetraphenylporphyrins in which the introduction of pyrrole {beta} substituents forces the molecules to adopt severely distorted saddle conformations, e.g. 2,3,7,8,12,13,17,18-octaethyl-5,10,15,20-tetraphenylporphyrin: OETPP. The macrocycle distortions not only alter the physical and chemical properties of the molecules but also exert significant geometric effects.