&bgr-Nitro-5,10,15-tritolylcorroles.

Functionalization of the &bgr;-pyrrolic positions of the corroie macrocycle with --NO2 groups Is limited at present to metallocorrolates due to the instability exhibited by corroie free bases under oxidizing conditions. A careful choice of the oxidant can limit the transformation of corroles into decomposition products or isocorroie species, preserving the corroie aromatidty, and thus allowing the insertion of nitro groups onto the corroie framework Here we report results obtained by reacting 5,10,lS-tritolylcorroIe (TTCorrH3) with the AgNO2/NaNO2 system, to give mono- and dinitrocorrole derivatives when stoichiometry is carefully controlled. Reactions were found to be regioselective, affording the 3-NO2TTCorrH3 and 3,17-(NO2)2TTCorrH3 isomers as the main products in the case of mono- and disubstitution, in 53 and 20% yields, respectively. In both cases, traces of other mono- and disubstituted isomers were detected, which were structurally characterized by X-ray crystallography. The influence of the &bgr;-nitro substituants on the corroie properties is studied in detail by UV--visible, electrochemical, and spectroelectrochemical characterization of these fimctionalized corroies. Density functional theory (DFT) and time-dependent DFT (TDDFT) calculations of the ground and excited state properties of these &bgr;-nitrocorrole derivatives also afforded significant information, dosely matching the experimental observations. It is found that the &bgr;-NO2 substituents conjugate with the Ä-aromatic system of the macrocycle, which initiates significant changes in both the spectroscopic and redox properties of the so fimctionalized corroies. This effect is more pronounced when the nitro group is introduced at the 2-position, because in this case the conjugation is, for steric reasons, more efficient than in the 3-nitro isomer. [ABSTRACT FROM AUTHOR]