Metal (Co, Fe) tribenzotetraazachlorin–fullerene conjugates: Impact of direct π-bonding on the redox behaviour and oxygen reduction reaction

• Published in: Electrochemistry communications 2009-06, Vol.11 (6), p.1221-1225
• Main Authors: Ozoemena, Kenneth I., Mamuru, Solomon A., Fukuda, Takamitsu, Kobayashi, Nagao, Nyokong, Tebello
• Format: Article
• Language: English
• Subjects: Chemistry; Coordination compounds; Cyclic voltammetry; Electrochemistry; Electrodes: preparations and properties; Exact sciences and technology; General and physical chemistry; Inorganic chemistry and origins of life; Kinetics and mechanism of reactions; Metal (Fe, Co) phthalocyanine–C 60; Other electrodes; Oxygen reduction; Preparations and properties; RDE experiment
• ISSN: 1388-2481; 1873-1902
• DOI: 10.1016/j.elecom.2009.04.011

Novel hexabutylsulphonyltribenzotetraazachlorin–fullerene (C 60) complexes of iron (FeHBSTBTAC–C 60) and cobalt (CoHBSTBTAC–C 60) have been synthesized and their electrochemistry and oxygen reduction reaction (ORR) compared with their octabutylsulphonylphthalocyanine analogues (FeOBSPc and CoOBSPc). It is proved that electron-withdrawing substituents (–SO 2Bu and C 60) on phthalocyanine macrocycle exhibit distinct impact on the solution electrochemistry of these metallophthalocyanine (MPc) complexes. The more electron-withdrawing C 60 substituent suppressed ORR compared to the –SO 2Bu in alkaline medium. FeOBSPc showed the best ORR activity involving a direct 4-electron mechanism, a rate constant of ∼1 × 10 8 cm 3 mol −1 s −1 and a Tafel slope of −171 mV dec −1.