Stable [48]-, [50]-, and [52]dodecaphyrins(1.1.0.1.1.0.1.1.0.1.1.0): the largest Hückel aromatic molecules

Abstract

[52]Dodecaphyrin(1.1.0.1.1.0.1.1.0.1.1.0) was quantitatively oxidized with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) to the corresponding [50]dodecaphyrin. Further oxidation of [50]dodecaphyrin with MnO2 quantitatively afforded [48]dodecaphyrin. Of the three, [50]dodecaphyrin showed Hückel aromatic character as the largest aromatic molecule reported to date. Protonation of [50]dodecaphyrin with methanesulfonic acid (MSA) led to the formation of a planar tetraprotonated species that displayed a sharp and intense Soret-like band at 906 nm with ε=6.5×10(5) M(-1) cm(-1) and Q-band-like bands at 1346 and 1600 nm.

Keywords: aromaticity; dodecaphyrins; expanded porphyrins; planar molecules; protonation.