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 photo-sensitizers.