Metal (Co, Fe) tribenzotetraazachlorin-fullerene conjugates: impact of direct p-bonding on the redox behaviour and oxygen reduction reaction (original) (raw)

Novel hexabutylsulphonyltribenzotetraazachlorin-fullerene (C 60) complexes of iron (FeHBSTBTAC-C 60) 25 and cobalt (CoHBSTBTAC-C 60) have been synthesized and their electrochemistry and oxygen reduction 26 reaction (ORR) compared with their octabutylsulphonylphthalocyanine analogues (FeOBSPc and CoO-27 BSPc). It is proved that electron-withdrawing substituents (-SO 2 Bu and C 60) on phthalocyanine macrocy-28 cle exhibit distinct impact on the solution electrochemistry of these metallophthalocyanine (MPc) 29 complexes. The more electron-withdrawing C 60 substituent suppressed ORR compared to the-SO 2 Bu 30 in alkaline medium. FeOBSPc showed the best ORR activity involving a direct 4-electron mechanism, a 31 rate constant of $1 Â 10 8 cm 3 mol À1 s À1 and a Tafel slope of À171 mV dec À1. 32