“Hetero-Multifunctionalization” of Gallium Corroles: Facile Synthesis, Phosphorescence, Redox Tuning, and Photooxidative Catalytic Improvement

Bromination of tris- and tetrakis-trifluoromethylated gallium corroles (3CF₃−Ga and 4CF₃−Ga) afforded tetrabrominated species 3CF₃−4Br−Ga and 4CF₃−4Br−Ga (yields: 20 % and 25 %) characterized by NMR, UV-vis spectroscopy, and mass spectrometry. Red-shifted absorption and emission bands were found; 3CF₃−4Br−Ga and 4CF₃−4Br−Ga displayed 5–12 nm shifts in their Soret bands and 8–17 nm shifts for their Q bands, compared to the respective nonbrominated species (3CF₃−Ga and 4CF₃−Ga). The respective Φ_F values were found to be 0.013 and 0.016; phosphorescence (lifetime=0.23 μs) was observed for 3CF₃−4Br−Ga (anaerobic, RT). The effect of tetrabromination on redox potentials (0.89 and 0.99 V) gave a 85 mV shift per Br atom in the reduction potential. 4CF₃−4Br−Ga allows for efficient catalytic photooxidative Br⁻ to Br₂ conversion compared to the β-octa-Br system (Br₈−Ga) structurally characterized here. This “hetero-multifunctionalization” approach, that is, is substitution with different sets of β-substituents, can help optimize porphyrinoid properties.