Synthesis of π-Ring-Fused Porphyrin(2.1.1.1)s and Their Rh(I) Complexes.

Stable and simplest expanded porphyrins, π-ring-fused porphyrin(2.1.1.1)s and Rh(I) complexes, have been obtained for the first time. Two free bases show chair-shaped molecular conformations, as if reassembled by the halves of porphyrin(1.1.1.1) and porphyrin(2.1.2.1). The insertion of Rh(CO) 2 groups induced more twisted molecular conformations. The NMR spectra, X-ray structure, NICS, and ACID of obtained molecules all support their nonaromaticity due to chair-shaped molecular conformations. The protonated and Rh(I) coordination of porphyrin(2.1.1.1)s process red-shifted absorptions in the NIR region.