Protoporphyrine cobalt complexes

The cobalt(n) complexes of protoporphyrin-IX dimethylester and mesoporphyrin-IX dimethylester have been reduced polarographically.113 The original study by Stynes and Ibers114 of the oxygenation of the amine complexes of cobalt(n) protoporphyrin-IX dimethylester has been criticized by Guidry and Drago,115 who suggest that the treatment of the data was incorrect and that the system is ill-defined. Ibers et al.116 have reconsidered their data and claim that this substantiates the earlier work and proves that the system is clearly defined. 

Several different sequences of reactions may be postulated for the conversion of the magnesium complexes of pheophytlns (chlorophylls) and Iron complexes of protoporphyrin IX and related porphyrins (hemes and hemlns) Into the nickel and vanadium porphyrins found In petroleum. One possible reason for the Isolation of only the nickel and oxovanadlum metalloporphyrlns Is that only they were resistant to degradation. While studies of Hodgson do Indicate that complexatlon of vanadium and nickel do Impart added thermal stability to porphyrins (12). Berezin has found that complexatlon of other metal Ions such as cobalt and copper also Imparts added thermal stability (13. 14). In addition, Hodgson s study Indicates that relatively little thermal degradation of the metalloporphyrlns has taken place In most crude oils (which would lead to unbound vanadium and nickel), One would expect that if little degradation of these metalloporphyrlns has occurred, complete disappearance of other metalloporphyrlns by thermal degradation Is an unreasonable assumption. 

Cobalt(I I )-protoporphyrin IX-reconstitu-ted Mb has also been found to form an affinity complex with MP-11 mono-layer electrodes [338, 339]. The association constant of the affinity complex between the reconstituted Mb and MP-11 corresponds to = 1.6 x 10 M , and the electron-transfer rate constant in... 

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