Synthesis of beta-Linked Diporphyrins and Their Homo- and Hetero-Bimetallic Complexes

beta-Meta- and -para-linked diporphyrins have been synthesized from two complementary routes using Suzuki cross-coupling and Adler condensation. Porphyrin boronate 6 cross couples with beta-monobromoporphyrin 2 to give unsymmetrically substituted porphyrin dimer 7c in high yield, and Adler condensation of beta-formylphenyltetraphenylporphyrins 9b,c with aryl aldehydes yields electronically tunable diporphyrins 7a-e. The homo- and hetero-bimetallic complexes 11a-c have been synthesized. Selective mono-metalation with zinc acetate at the beta-substituted site has been found for 7a. The Zn-Co diporphyrin complex 11c undergoes strong emission quenching compared to that of the diporphyrin 11a and dizinc diporphyrin 11b.