Spectroscopic studies of the interaction of cobalt(II) N,N′,N″,N″′-tetramethyltetra-3,4-pyridinoporphyrazine with amino acids and nitrogen oxides

✍ Scribed by Mamothibe A. Thamae; Tebello Nyokong

• Publisher: John Wiley and Sons
• Year: 2001
• Tongue: English
• Weight: 130 KB
• Volume: 05
• Category: Article
• ISSN: 1088-4246
• DOI: 10.1002/jpp.551

✦ Synopsis

The interaction of histidine, cysteine, NO and nitrite with cobalt(II) N,N',N″,N‴-tetramethyltetra-3,4-tetrapyridinoporphyrazine ([ Co ^II^ tmtppa ]^4+^) is reported. Metal-based autoreduction of [ Co ^II^ tmtppa ]^4+^ occurs with the formation of the [ Co ^I^ tmtppa (-2)]^3+^ species in the presence of histidine and cysteine. Kinetic data for the auto reduction of [ Co ^II^ tmtppa ]^4+^ in the presence of these amino acids gave the rate constants k ~f~ = 2.1 × 10^1^ and 2.8 dm^3^ mol^-1^ s^-1^, for cysteine and histidine, respectively. One molecule of NO or nitrite was found to coordinate to the [ Co ^II^ tmtppa ]^4+^ species. The equilibrium and rate constants for the coordination of the nitric oxide were K = 2.3 × 10^4^ dm ^3^ mol ^-1^ and k ~f~ = 7.5 dm ^3^ mol ^-1^ s ^-1^, respectively. The coordination of nitrite to [ Co ^II^ tmtppa ]^4+^ occurred with an equilibrium constant of K = 2.0 × 10^2^ dm ^3^ mol ^-1^ and a rate constant of k ~f~ = 4.0 × 10^-3^ dm ^3^ mol ^-1^ s ^-1^. There was no evidence for the coordination of two molecules of nitrite to the [ Co ^II^ tmtppa ]^4+^ species.