Inorganic Chemistry
Article
CV and RDV data of tetracarboxylated FePc32a and other iron
porphyrins,32b,c this may be due to the reduction of H2O2
occurring at or slightly more negative potentials than that of the
process from O2 to H2O2.
For mass transport controlled processes, the number of
electrons involved in the half reactions is related to the limiting
current and rotation rate, as described by the Levich equation
(eq 7):
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was partly supported by a Grant-in-Aid for Scientific
Research on Innovative areas (No. 20108007, “pi-Space”),
Scientific Research (B) (No. 23350095), and Young Scientist
(B) (No. 24750031) from the Ministry of Education, Culture,
Sports, Science, and Technology (MEXT).
iL = 0.62nFAD2/3C0v−1/6ω1/2
(7)
REFERENCES
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Here iL is the Levich current, n is the number of electrons
transferred in the half reaction, F is the Faraday constant (96
500 C mol−1), A is the electrode’s area (0.196 cm2), D is the
diffusion coefficient of O2 in the buffer solutions (1.7 × 10−5
cm2 s−1), v is the kinematic viscosity of the solution (0.01 cm2
s−1), C0 is the concentration of oxygen in solution (1.3 × 10−3
mol L−1), and ω is the angular rotation rate of the electrode
(rad s−1).10a,33
Plots of current density (I) versus rotation rate resulted in
linear curves in which the number of electrons n was calculated
from the angular coefficient (Figure 11). The values of n found
for the bare electrode and that coated with 2a were 1.8 and 1.7,
respectively, which indicate that the catalysis proceeds via a
two-electron mechanism (eq 5), with formation of the peroxide
anion. Compound 2b, however, shows n equal to 2.8. From the
data in Figures 9 and 10, this value may indicate a 2 + 2
mechanism, which consists of a first complete O2 to H2O2
process and a subsequent incomplete H2O2 to H2O process.
This often occurs for mononuclear FePcs and iron porphyr-
ins.32
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ASSOCIATED CONTENT
* Supporting Information
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S
Additional spectroscopic results of the studied phthalocyanines.
This material is available free of charge via the Internet at
AUTHOR INFORMATION
Corresponding Author
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(13) (a) Durmus, M.; Ahsen, V. J. Inorg. Biochem. 2010, 104, 297−
309. (b) Li, H.; Jensen, T. J.; Fronczek, F. R.; Vicente, G. H. J. Med.
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dx.doi.org/10.1021/ic4002048 | Inorg. Chem. XXXX, XXX, XXX−XXX