Expanded porphyrins have been widely studied in their specific characteristics of NIR absorption and emission, non-linear optics, versatile electronic states, and multinuclear metal complexes. Generally, porphyrin and related compounds consist of one meso-carbon between pyrrole units, which usually provide the planar and rigid structures. On the other hand, an increase of the numbers of meso-carbons and pyrroles forms flexible frameworks in the formation of bent and distorted structures. Recently, we succeeded to synthesize aromatic rings–fused porphyrin(2.1.2.1) from dipyrrolylbenzene (DPB) [1] and a series of porphyrin(2.1.2.1), hexaphyrin(2.1.2.1.2.1) and octaphyrin(2.1.2.1.2.1) from diphenyldipyrrolylethene (DPDPYE). These porphyrins have unique bent and distorted structures, which are revealed by X-ray crystallography. Porphyrin(2.1.2.1) and hexaphyrin(2.1.2.1.2.1) work as nuclear ligands, which are able to be converted to various metal complexes. The electronic, optical and electrochemical properties and single crystal structures of these expanded porphyrins will be discussed.

Reference

[1] Kuzuhara, D.; Furukawa, W.; Kitashiro, A.; Aratani, N.; Yamada, H. Chem. Eur. J. 2016, 22, 10671.