Cofacial porphyrin dimers have attracted a considerable attention due to their potential as artificial reaction centers in the photosystem, bimetallic catalysts and function as host molecule. However, their syntheses have required troublesome multi-step reactions. Recently, we have reported a facile and efficient synthetic method for meso-heteroatom-substituted porphyrins from the corresponding meso-bromoporphyrins via the catalyst-free aromatic nucleophilic substitution (S_NAr) reactions.^1,2,3 In this work, we applied this efficient method to the synthesis of cofacial porphyrin dimers bridged by the dihydroxyarene derivatives. Reaction of resorcinol with an excess of meso-bromoporphyrin in the presence of base afforded the acyclic dimers 1 in good yield. The steric hindrance between porphyrin and substituents on resorcinol determined their formations. For example, 4,6-diethylresorcinol gave cofacial conformation whereas 2-methylresorcinol gave open conformation. Reaction of resorcinol or 2,7-dihydroxynaththalene with meso-dibromoporphyrin afforded cyclic porphyrin dimers 2 and 3 with rigid cofacial conformation in good yield. We will also report the synthesis, structural characterization, and physical properties of the obtained dimer and their metal complexes.

References

(1) K. Yamashita, K. Kataoka, M. S. Asano, K. Sugiura, Org. Lett. 2012, 14, 190–193.

(2) K. Yamashita, S. Sakamoto, A. Suzuki, K. Sugiura, Chem. Asian J. 2016, 11, 1004–1007.

(3) K. Yamashita, K. Kataoka, S. Takeuchi, M. S. Asano, K. Sugiura, J. Org. Chem. 2016, 81, 11176–11184.