Undecaphenylcorroles

A first major study of undecaphenylcorrole (UPC) derivatives
is
presented. Three different Cu-UPC derivatives with different para
substituents X (X = CF3, H, CH3) on the β-aryl
groups were synthesized via Suzuki–Miyaura coupling of Cu­[Br8TPC] and the appropriate arylboronic acid. A single-crystal
X-ray structure of the X = CF3 complex revealed a distinctly
saddled macrocycle conformation with adjacent pyrrole rings tilted
by ∼60–66° relative to one another (within the dipyrromethane units), which is somewhat higher than that observed for β-unsubstituted
Cu-TPC derivatives but slightly lower than that observed for Cu­[Br8TPC] (∼70°) derivatives.
Electrochemical and electronic absorption measurements afforded some
of the first comparative insights into meso versus β substituent
effects on the copper corrole
core. The Soret maxima of the Cu-UPC complexes (∼440–445
nm), however, are comparable to those of Cu­[Br8TPC] derivatives
and are considerably red-shifted relative to Cu-TPC derivatives. Para
substituents
on the β-phenyl groups were found to tune the redox
potentials of copper corroles more effectively than those on meso-phenyl substituents, a somewhat surprising observation
given that neither the HOMO nor LUMO has significant amplitudes at
the β-pyrrolic
positions.