One pot synthesis of unusual meso-dipyrrinyl corrole

Abstract

We have synthesized an unusual meso-dipyrrinyl corrole 1 in one pot reaction using 2 + 1 approach, by condensing pentafluorobenzaldehyde with meso-free dipyrromethane under TFA catalyzed reaction conditions followed by oxidation with a mild oxidant such as p-chloranil. The product was not obtained when we used other aldehydes such as p-nitrobenzaldehyde and p-cyanobenzaldehyde as well as when we changed the oxidant from p-chloranil to DDQ. We elucidated the molecular structure of 1 using detailed 1D and 2D NMR spectroscopy. The absorption spectrum showed typical Soret band and three Q-bands with slight shifts in the peak maxima compared to meso-free corrole. The meso-dipyrrinyl corrole was decently fluorescent and showed emission band at 678 nm. The preliminary study showed that the meso-free carbon of meso-dipyrrinyl corrole was sufficiently reactive for functionalization but the resulted functionalized meso-dipyrrinyl corroles were not stable to isolate. Our attempts to prepare metal complexes of meso-dipyrrinyl corroles remained unsuccessful because of the unstable nature of the resulted coordination complexes.