Zwitterionic corroles: regioselective nucleophilic pyridination of a doubly linked biscorrole.

Pyridine attacks: Nucleophilic addition of pyridine derivatives to a doubly linked corrole, which is a stable singlet biradical species, occurs at the bay area with high regioselectivity to provide zwitterionic dimers (see picture; Ar = C(6)F(5)). Charge transfer between the anionic corrole and the pyridinium groups induces effective fluorescence quenching of the corrole dimer, which can be utilized for selective fluoride ion recognition.