Substituent effects on metallophthalocyanines adsorbed on graphite on their activity for the electrooxidation of hydrazine.

Content Provider	Semantic Scholar
Author	Geraldo, Daniela A. Linares, Cristian Zagal, José H.
Copyright Year	2002
Abstract	In this work we have examined the effect of substituents on phthalocyanines of cobalt and iron on their catalytic activity for the electrooxidation of hydrazine. The activity of the different substituted phthalocyanines was examined by adsorbing them on graphite electrodes. The complexes used with electron-donating groups were: cobaltoctaethylhexyloxyphthalocyanine (CoOEHPc); cobalttetraneopentoxyphthalocyanine (CoTNPPc); cobalttetramethoxyphthalocyanine (CoMeOPc) cobalttetraaminophthalocyanine (CoTAPc) and cobalt-2,3 naphthalocyanine (CoNPc). Unsubstituted cobaltphthalocyanine (CoPc) was also used. Complexes with electron-withdrawing groups were cobalttetranitrophthalocyanine (CoTNPc) and cobaltdodecafluorophthalocyanine (CoPcF16). Fig.1 shows typical results obtained for the oxidation of hydrazine catalyzed with cobalt phthalocyanines substituted with both electron-donating (left part of the curve) and electron-withdrawing (right part of the curve) groups on the periphery of the ligand. The data is presented as a plot of log I (at constant potential) versus Co(II) /(I) formal redox potential of the catalyst. For some complexes (on the right) the rate of the reaction increases with the driving force of the catalyst (measured as it redox potential) but for those on the left it decreases. The same plot is obtained when plotting log I versus the sum of the Hammett parameters of the substituents on the periphery of the phthalocyanine ring. A similar curve is obtained when the ligand is kept the same (phthalocyanine) and the metal is varied (Cr,Mn,Fe,Ni and Cu) and log I is plotted versus the number of d-electrons of the central metal. Results similat to those in Fig.1 are obtained when using iron unsubstituted phthalocyanine (FePc) and substituted iron phthalocyanines with electron-donating groups irontetramethoxyphthalocyanine (FeMeOPc) irontetraaminophthalocyanine (FeTAPc) irontetracarboxyphthalocyanine (FeTCPc) iron-2,3 naphthalocyanine (FeNPc) and with electron-withdrawing groups were iron-tetranitrophthalocyanine (FeTNPc) and iron-dodecachlorophthalocyanine (FePcF16).
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Resource Type	Article