Carbazole-corrole and carbazole-prophyrin dyads: Synthesis, fluorescence and electrochemical studies

Donor-acceptor type carbazole-corrole and carbazole-porphyrin dyads 4-9 were synthesized and characterized. Corrole and porphyrin containing one meso-p-iodophenyl group were coupled to N-butyl-3-ethynyl-carbazole by a modified Sonogashira reaction. All the dyads were characterized by HRMS mass, NMR, UV-vis absorption, fluorescence and electrochemical techniques. Fluorescence studies of dyads 4, 7 and 8 indicated energy transfer from the donor carbazole moiety to the corresponding acceptor corrole/porphyrin moiety (up to 80%). The electron-releasing N-butyl-carbazole group affects the electronic properties of the corrole and porphyrin macrocycles in the dyads 4-9. Electrochemical studies revealed that dyads 4 and 5 are difficult to reduce compared to their corresponding monomers, as reflected by the cathodic shift in their reduction potentials. Meanwhile, dyads 6-9 exhibited an anodic shift in their reduction potentials, suggesting that they are easy to reduce compared to their corresponding monomers.