Nitrocorroles have recently been studied as potential agents against human cytomegalovirus infection for their antiviral activity.¹ They have also been incorporated into triple-decker complexes containing phthalocyanine macrocycles.² The nitrophenyl corroles can undergo multiple redox reactions at the conjugated macrocycle in addition to one or more reductions at the meso-nitrophenyl groups. Metal-centered reactions can also occur for some transition metal corroles. As part of our continuing studies into elucidating the electrochemistry of porphyrins, corroles and related macrocycles, we have synthesized a series of free-base and metallated nitrophenylcorroles which were electrochemically characterized in a variety of nonaqueous solvents. The structures of the investigated compounds are shown in Chart 1. The redox potentials for each electrode reaction of the above compounds were measured by cyclic voltammetry and spectra of the electroreduced and electroxidized forms of the corrloles were obtained by thin-layer UV-visible spectroelectrochemistry under the same solution condition. This data was then analyzed as a function of the solvent properties, the number and position of the meso-nitrophenyl substituents and the type or oxidation state of the central metal ion. Protonation and deprotonation constants of the free-base corroles were also determined by monitoring changes in the UV-visible spectra during titrations with different acids or bases. The free-base corroles can add one proton to form CorH₄⁺ and they can also lose one or two protons to form CorH₂^- and possibly CorH^-. These positively and negatively charged corroles are also electroactive and were characterized as to their electrochemistry and spectral properties.

1. Gros, C. P.; Desbois, N.; Michelin, C.; Demilly, E.; Tilkin-Mariame, A.-F.; Mariame, B.; Gallardo, F. ACS Infect. Dis. 2015, 1(8), 350-356.

2. Lu, G.; Li, J.; Jiang, X.; Ou, Z.; Kadish, K. M. Inorg. Chem. 2015, 54 (18), 9211-9222.