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

Abstract

Bromination of tris- and tetrakis-trifluoromethylated gallium corroles (3CF(3)-Ga and 4CF(3)-Ga) afforded tetrabrominated species 3CF(3)-4Br-Ga and 4CF(3)-4Br-Ga (yields: 20 % and 25 %) characterized by NMR, UV-vis spectroscopy, and mass spectrometry. Red-shifted absorption and emission bands were found; 3CF(3)-4Br-Ga and 4CF(3)-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 (3CF(3)-Ga and 4CF(3)-Ga). The respective phi(F) values were found to be 0.013 and 0.016; phosphorescence (lifetime=0.23 mu s) was observed for 3CF(3)-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. 4CF(3)-4Br-Ga allows for efficient catalytic photooxidative Br- to Br-2 conversion compared to the beta-octa-Br system (Br-8-Ga) structurally characterized here. This "hetero-multifunctionalization" approach, that is, is substitution with different sets of beta-substituents, can help optimize porphyrinoid properties.