Porphyrins and Corroles with 2,6-Pyrimidyl Substituents

Corroles and porphyrins with 2,6-pyrimidyl substituents are reported for the first time, together with the spectroscopic data and the crystal structures of the free-base porphyrin and of the phosphorus and cobalt complexes of the corrole

Tuning the Photophysical and Redox Properties of Metallocorroles by Iodination

Facile procedures were developed for selective iodination of aluminum and gallium corroles; crystallographic characterization shows that the main structural aspects are not changed (the macrocycle remains planar). Absorption maxima are red-shifted by 3–5 nm/iodine, singlet lifetimes are reduced to <80 ps, and emissions from long-lived excited states come into effect. The iodinated corroles display prompt fluorescence, phosphorescence, and delayed thermal fluorescence, all at room temperature. The effect on redox potentials appears to be additive for each additional iodine and, surprisingly, is practically identical to that of the other three halides. The conclusions of this work are of large importance for the design of metallocorroles that are best suited for the various applications where metallocorroles are used as catalysts and photosensitizers

Tuning the Photophysical and Redox Properties of Metallocorroles by Iodination

Facile procedures were developed for selective iodination of aluminum and gallium corroles; crystallographic characterization shows that the main structural aspects are not changed (the macrocycle remains planar). Absorption maxima are red-shifted by 3–5 nm/iodine, singlet lifetimes are reduced to <80 ps, and emissions from long-lived excited states come into effect. The iodinated corroles display prompt fluorescence, phosphorescence, and delayed thermal fluorescence, all at room temperature. The effect on redox potentials appears to be additive for each additional iodine and, surprisingly, is practically identical to that of the other three halides. The conclusions of this work are of large importance for the design of metallocorroles that are best suited for the various applications where metallocorroles are used as catalysts and photosensitizers

Variables That Influence Cellular Uptake and Cytotoxic/Cytoprotective Effects of Macrocyclic Iron Complexes

Determination of the cellular uptake of macrocyclic iron­(III) complexes by a facile method, accompanied by cell viability tests under both basal and induced oxidative stress, demonstrates that protection against <i>intracellular</i> oxidative stress requires reasonably high internalization and favorable anti/prooxidant profiles. Of the four tested complexes, only amphipolar iron­(III) corrole met these criteria

5d Early-Transition-Metal Corroles: a Trioxo-Bridged Binuclear Tungsten(VI) Derivative

The synthesis and full characterization of the first tungsten corrole reveal that it is a binuclear trioxo-bridged complex of tungsten­(VI), a coordination motif without precedence for tungsten chelated by other ligands

Intriguing Chemistry of Molybdenum Corroles

The development of new methodologies for gaining access to low-valent molybdenum complexes led to spectroscopic identification of mononuclear (oxo)­molybdenum­(IV) corroles, as well as the full characterization of a binuclear molybdenum­(IV) corrole that is bridged through axial O atoms by a Mg­(THF)₄ moiety

Intriguing Chemistry of Molybdenum Corroles

The development of new methodologies for gaining access to low-valent molybdenum complexes led to spectroscopic identification of mononuclear (oxo)­molybdenum­(IV) corroles, as well as the full characterization of a binuclear molybdenum­(IV) corrole that is bridged through axial O atoms by a Mg­(THF)₄ moiety

Reactive Intermediates Involved in Cobalt Corrole Catalyzed Water Oxidation (and Oxygen Reduction)

A detailed investigation of the cobalt corrole Co­(tpfc) as molecular catalyst for electrochemical water oxidation uncovered many important mechanism-of-action details that are crucial for the design of optimally performing systems. This includes the identification of the redox states that do and do not participate in catalysis and very significant axial ligand effects on the activity of the doubly oxidized complex. Specifics deduced for the electrocatalysis under homogeneous conditions include the following: the one-electron oxidation of the cobalt­(III) corrole is completely unaffected by reaction conditions; catalysis coincides with the second oxidation event; two catalytic waves develop in the presence of OH^–, and the one at lower overpotential is dominant under more basic conditions. Comparative spectroelectrochemical measurements performed for Co­(tpfc) and Al­(tpfc), the analogous corrole chelated by the nonredox active aluminum, revealed that the second oxidation process of Co­(tpfc) is much more significantly metal-centered than the first one. EPR studies revealed that shift from fully corrole-centered to partially metal-centered in the singly oxidized complex [Co­(tpfc)]⁺ is achievable with fluoride as axial ligand. The analogous experiment, but with hydroxide instead of fluoride, could not be performed because of a surprising phenomenon: formation of a cobalt–superoxide complex that is actually relevant to oxygen reduction rather than to water oxidation. Nevertheless, fluoride and hydroxide induce very similar effects in terms of the appearance of two catalytic waves, lowering of onset potentials, and increasing the catalytic activity. The main conclusions from the accumulated data are that the apparent pH effect is actually due to hydroxide binding to the cobalt center and that π-donating axial ligands play pivotal and beneficial roles regarding the main factors that are important for facilitating the oxidation of water

Surprising Route to a Monoazaporphyrin and Full Characterization of Its Complexes with Five Different 3d Metals

In the search for mild agents for the oxidative cyclization of tetrapyrromethane to the corresponding corrole, we discovered a route that leads to a monoazaporphyrin with three meso-CF3 groups. Optimization studies that allowed access to appreciable amounts of this new macrocycle paved the way for the preparation of its cobalt, copper, nickel, zinc, and iron complexes. All complexes were fully characterized by various spectroscopic methods and X-ray crystallography. Their photophysical and electrochemical properties were determined and compared to those of analogous porphyrins in order to deduce the effect of the peripheral N atom. Considering the global efforts for designing efficient alternatives to platinum group metal (PGM) catalysts, they were also absorbed onto a porous carbon electrode material and studied as electrocatalysts for the oxygen reduction reaction (ORR). The cobalt complex was found to be operative at a quite positive catalytic onset potential and with good selectivity for the desirable 4-electrons/4-protons pathway

Expected and Unexpected Transformations of Manganese(III) Tris(4-nitrophenyl)corrole

The synthesis and characterization of manganese complexes of 5,10,15-tris­(4-nitrophenyl) corrole in different oxidation states are described. Adoption of established protocols for the synthesis of (nitrido)­manganese­(V) complexes led to the expected corrole derivative as a minor product, accompanied by nitrogen atom insertion into the macrocycle. The major product was fully characterized via the combination of spectroscopy and X-ray crystallography as (nitrido)­manganese­(V) 6-azahemiporphycene