The one-electron oxidation of hydroxy(tetramesitylporphyrinato)iron(III)

2000 ◽  
Vol 78 (10) ◽  
pp. 1318-1324
Author(s):  
David H Jones ◽  
A Scott Hinman
Keyword(s):  
Electron Transfer ◽  
Cyclic Voltammetry ◽  
Oxidation Product ◽  
Supporting Electrolyte ◽  
Cation Radical ◽  
Time Dependent ◽  
Porphyrin Ring ◽  
Initial Oxidation ◽  
Heterogeneous Electron Transfer ◽  
The One

The oxidation of hydroxy(tetramesitylporphyrinato)Fe(III) ([Fe(tmp)]OH) has been investigated by voltammetric and spectroelectrochemical techniques in CH2Cl2 containing tetra(n-butyl)ammonium hexafluorophosphate as supporting electrolyte. In this medium, the first one-electron oxidation is reversible on the time scale of cyclic voltammetry. The UV–vis spectrum, as obtained by double potential step chronoabsorptometry, indicates that the oxidation is centered at the porphyrin ring to form the corresponding π-cation radical. At longer times, or higher potentials, oxidation of [Fe(tmp)]OH leads to loss of hydroxide and formation of [Fe(tmp+)]PF6 π-cation radical. The time-dependent process is consistent with an ECE type mechanism, with the chemical step being slow conversion to neutral [Fe(tmp)]PF6. At higher potentials, the initial oxidation product loses a second electron. The overpotential dependent oxidation suggests an EEC type mechanism with the second electrochemical step being a slow heterogeneous electron transfer from the Fe-OH moiety.Key words: hydroxy(tetramesitylporphyrinato)iron(III), oxidation, electrochemistry, spectroelectrochemistry, π-cation radical.

In situ Fourier transform infrared spectroelectrochemical studies of the oxidation of some octaethylporphyrin complexes

1993 ◽  
Vol 71 (12) ◽  
pp. 1975-1982 ◽  
Author(s):  
A. Scott Hinman ◽  
Temitayo Olorunyolemi
Keyword(s):  
Cation Radical ◽  
Porphyrin Ring ◽  
In Situ Ftir ◽  
Metal Centre ◽  
Initial Oxidation ◽  
Porphyrin Ligand ◽  
Spectral Changes ◽  
Marker Band ◽  
Absorbance Band

The oxidations of OEPNi(II), OEPCu(II), OEPFe(III)Cl, OEPMn(III)ClO4, OEPAg(II), OEPCo(II), and OEPZn(II) (OEP = 2,3,7,8,12,13,17,18-octaethylporphyrin dianion) have been studied by in situ FTIR reflectance spectroelectrochemistry in dibromomethane. One-electron oxidation of the porphyrin ring to produce a π-cation radical results in the appearance of a strong new absorbance band near 1550 cm−1. Other features typical of π-cation radical formation are a strong absorbance increase near 1470 cm−1, and absorbance decreases near 1270 and 1018 cm−1. Oxidation of the metal centre, as observed for OEPCo(II) in the presence of CH3CN, and for OEPAg(II), results in considerably less perturbation of the vibrational spectra of the complexes. For OEPCo(II) in dry dibromomethane, initial oxidation at the porphyrin ligand is followed by a second oxidation at the metal centre. This order is reversed when acetonitrile is added to solution. Production of porphyrin π-dications was observed for OEPCu(II) and OEPNi(II). This results in a shift of the 1550 cm−1 π-cation radical marker band to higher energy, and a strong absorbance increase near 1380 cm−1. Unusual spectral changes observed on one-electron oxidation of OEPZn(II) are suggested to result from the formation of a dimer.

scholarly journals Reduction of ferric haemoproteins by tetrahydropterins: a kinetic study

2005 ◽  
Vol 392 (3) ◽  
pp. 583-587 ◽  
Author(s):  
Chantal Capeillere-Blandin ◽  
Delphine Mathieu ◽  
Daniel Mansuy
Keyword(s):  
Electron Transfer ◽  
Cytochrome C ◽  
Cytochrome B5 ◽  
Reduction Rate ◽  
Cation Radical ◽  
Order Reduction ◽  
Reduction Potentials ◽  
Electron Reduction ◽  
The One

We previously showed that one-electron transfer from tetrahydropterins to iron porphyrins is a very general reaction, with formation of an intermediate cation radical similar to the one detected in NO synthase. As a model reaction, the rates of reduction of eight haemoproteins by diMePH4 (6,7-dimethyltetrahydropterin) have been studied and correlated with their one-electron reduction potentials, Em (FeIII/FeII). On the basis of kinetic data analyses, a bimolecular collisional mechanism is proposed for the electron transfer from diMePH4 to ferrihaemoproteins. Haemoproteins with reduction potentials below −160 mV were shown not to be reduced by diMePH4 to the corresponding ferrohaemoproteins. For haemoproteins with reduction potentials more positive than −160 mV, such as chloroperoxidase, cytochrome b5, methaemoglobin and cytochrome c, there was a good correlation between the second-order reduction rate constant and the redox potential, Em (FeIII/FeII):The rate of reduction of cytochrome c by BH4 [(6R)-5,6,7,8-tetrahydrobiopterin] was determined to be similar to that of the reduction of cytochrome c by diMePH4. These results confirm the role of tetrahydropterins as one-electron donors to FeIII porphyrins.

Kinetics and electrochemical studies of uranium in acetate and formate media by cyclic voltammetry

2007 ◽  
Vol 95 (12) ◽  
Author(s):  
A. S. A. Khan ◽  
Riaz Ahmed ◽  
M. L. Mirza
Keyword(s):  
Cyclic Voltammetry ◽  
Transfer Rate ◽  
Supporting Electrolyte ◽  
Electrochemical Studies ◽  
Hanging Mercury Drop Electrode ◽  
Electron Transfer Rate ◽  
Cyclic Voltammetric ◽  
Heterogeneous Electron Transfer ◽  
Electron Transfer Rate Constant ◽  
Voltammetric Behavior

SummaryThe cyclic voltammetric behavior of uranyl ion was investigated at hanging mercury drop electrode in perchlorate supporting electrolyte. The standard heterogeneous electron transfer rate constant “

The role of supporting electrolyte in heterogeneous electron transfer

2017 ◽  
Vol 21 (7) ◽  
pp. 1833-1845 ◽  
Author(s):  
Galina A. Tsirlina
Keyword(s):  
Electron Transfer ◽  
Supporting Electrolyte ◽  
Heterogeneous Electron Transfer

scholarly journals Electrochemical Evidences for the Enhancement of Heterogeneous Electron Transfer Rates of Riboflavin in the Presence of Copper

2015 ◽  
Vol 62 (2) ◽  
pp. 147-152 ◽  
Author(s):  
Md Abdul Jabbar ◽  
Shaila Salahuddin ◽  
Rowshan Jahan Mannan ◽  
Abu Jafar Mahmood
Keyword(s):  
Electron Transfer ◽  
Cyclic Voltammetry ◽  
Carbon Electrode ◽  
Transfer Rates ◽  
Nuclear Complex ◽  
Heterogeneous Electron Transfer ◽  
Anodic Stripping ◽  
Overall Stability ◽  
Pulse Voltammetry ◽  
Good Agreement

Evidences for the enhancement of the heterogeneous electron transfer rates of riboflavin in the presence of copper in aqueous medium with a glassy carbon electrode were investigated by cyclic voltammetry, chronocoulometry and differential anodic stripping pulse voltammetry. It was found that copper exhibits a multi-nuclear complex with riboflavin in aqueous KCl solution. The overall stability constant of the complex was calculated (log? = 11.17), which is in a good agreement for the formation of a stable copper-riboflavin complex. DOI: http://dx.doi.org/10.3329/dujs.v62i2.21980 Dhaka Univ. J. Sci. 62(2): 147-152, 2014 (July)

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