Demetallization hydrogen peroxide

Regarding non-pyrolyzed macrocycles, hydrogen peroxide formed in the reduction cycle can lead to broken bonds between the substituents and the tetrapyrrole core. Changes in the electronic structure connected therewith cause a decrease of the reduction activity. In acidic conditions as given in PEM-FC, demetallation can also cause an activity decline [71, 87, 98, 102, 210, 211]. Furthermore, carbon monoxide is able to bind irreversibly to the metal centers and thereby deactivating them [212]. With respect to Eq. 16.7, carbon monoxide might be formed by carbon oxidation during FC operation. 

Demetallation was readily achieved by treatment with alkaline hydrogen peroxide... 

Abd-El-Aziz and coworkers have also reported the preparation of organoiron polymers containing azobenzene chromophores in their sidechains. Scheme 14 shows the synthesis of orange and red-colored cationic polymers (58) that absorbed between 417 and 489 nm. Polymers 58 were subsequently demetallated to produce their corresponding organic analogs (59). Photolysis of polymers 59 in the presence of hydrogen peroxide resulted in the decoloration of these polymers. 

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