Effect of Ring Distortion upon Redox Potentials of Metalloporphyrins: Electrochemical Studies of Metallododecaphenylporphyrins

1995 ◽  
Vol 24 (10) ◽  
pp. 939-940 ◽  
Author(s):  
Jun Takeda ◽  
Mitsuo Sato
Keyword(s):  
Electrochemical Studies ◽  
Redox Potentials ◽  
Ring Distortion

scholarly journals Substitution Effect on the Charge Transfer Processes in Organo-Imido Lindqvist-Polyoxomolybdate

Molecules ◽  
2018 ◽  
Vol 24 (1) ◽  
pp. 44 ◽  
Author(s):  
Patricio Hermosilla-Ibáñez ◽  
Kerry Wrighton-Araneda ◽  
Walter Cañón-Mancisidor ◽  
Marlen Gutiérrez-Cutiño ◽  
Verónica Paredes-García ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Theoretical Study ◽  
Bathochromic Shift ◽  
Substitution Effect ◽  
Spectroscopic Properties ◽  
Electrochemical Studies ◽  
Redox Potentials ◽  
Metal Centre ◽  
Transfer Processes ◽  
Organic Fragment

Two new aromatic organo-imido polyoxometalates with an electron donor triazole group ([n-Bu4N]2[Mo6O18NC6H4N3C2H2]) (1) and a highly conjugated fluorene ([n-Bu4N]2[Mo6O18NC13H9]) (2) have been obtained. The electrochemical and spectroscopic properties of several organo-imido systems were studied. These properties were analysed by the theoretical study of the redox potentials and by means of the excitation analysis, in order to understand the effect on the substitution of the organo-imido fragment and the effect of the interaction to a metal centre. Our results show a bathochromic shift related to the charge transfer processes induced by the increase of the conjugated character of the organic fragment. The cathodic shift obtained from the electrochemical studies reflects that the electronic communication and conjugation between the organic and inorganic fragments is the main reason of this phenomenon.

scholarly journals Electrochemical behaviours of Eu(III)/E(II) and Ce(IV)/Ce(III) in H3PO4-H2O media : solvation and complexation reactions

2018 ◽  
Vol 149 ◽  
pp. 01092
Author(s):  
B. Belqat ◽  
S. Belcadi
Keyword(s):  
Rare Earth ◽  
Phosphoric Acid ◽  
Rare Earth Elements ◽  
Electrochemical Properties ◽  
Essential Elements ◽  
High Tech ◽  
Electrochemical Studies ◽  
Redox Potentials ◽  
Complexation Reactions ◽  
Phosphoric Acid Concentration

Many kinds of rare earth elements (REE) such as europium and cerium have been make them essential elements in many high-tech components. The electrochemical studies can be presented as an interesting indication for europium and cerium extraction from phosphoric solutions, including solvation and complexation reactions. The normal redox potentials of Eu3+/Eu2+ and Ce4+/Ce3+ systems have been determined in H3PO4-H2O media with various phosphoric acid concentration. The solvation of these elements in phosphoric media is characterized by their transfer activity coefficients "f" calculated from the corresponding normal redox potentials. The corresponding solvation increases with increasing the H3PO4 concentration. For each REE, the electrochemical properties depend on its number of charges and on its basic properties. Results suggest that solvation and complexation of REE phosphates are important in controlling REE concentration.

Control of the Redox Potential by Oxygen Limitation Inhibits Bioleaching of Pyrite

2009 ◽  
Vol 71-73 ◽  
pp. 401-404 ◽  
Author(s):  
Biao Wu ◽  
Jian Kang Wen ◽  
Gui Ying Zhou ◽  
Ren Man Ruan
Keyword(s):  
Redox Potential ◽  
Dissolution Rate ◽  
Oxygen Limitation ◽  
Metal Sulfides ◽  
Electrochemical Studies ◽  
Redox Potentials ◽  
Nitrogen Gas ◽  
Copper Sulfides ◽  
Fe Content ◽  
Constant Potential

Based on the bioleaching mechanism and electrochemical studies of metal sulfides, the dissolution rate of secondary copper sulfides and pyrite are controlled by redox potentials. Experiment on the bioleaching of the secondary copper sulfides under constant potential by sparging with nitrogen gas demonstrated, by analyzing Cu and Fe content of the bioleaching solution and residues, the pyrite and secondary cooper sulfides dissolution rates have large difference in various redox potential. The pyrite and secondary cooper sulfides have good selection when the redox potential controlled between 700mV and 760mV, we can realize the secondary copper sulfides bioleaching process be controlled, then supply theoretical guide for the iron-acid balance during copper bioleaching process.

scholarly journals Electrochemical studies of grid and linear type M^2+ (M=Zn, Cd and Pb) complexes of a bis-(hydrazone) bearing two symmetric carboxylic groups

2018 ◽  
Vol 21 (1) ◽  
pp. 113
Author(s):  
Wilson Giraldo ◽  
Elkin Romero ◽  
Manuel Chaur
Keyword(s):  
Smart Materials ◽  
Spin Crossover ◽  
Electrochemical Studies ◽  
Redox Potentials ◽  
Linear Type ◽  
Wave Voltammetry ◽  
Carboxylic Groups ◽  
Different Temperatures ◽  
Linear Correlations ◽  
Transoid Conformation

Herein  we  present  the  preparation  of  a  bis-(hydrazone)  containing  a  pyridine-pyrimidine-pyridine framework. This compound can be visualized as a double arm system able of coordinating two metal ions in a terpyridine-like manner. By NMR (1D and 2D) it was determined a transoid conformation  and  an  E  configuration  around  the  two  imine  double  bonds.  Complexation  with M2+ (M = Zn, Cd, and Pb) ions resulted in grid and linear type structures which were studied by cyclic and squared wave voltammetry at different temperatures. No linear correlations of the redox potentials as a function of temperature were observed. The latter is likely due to rearrangements in the structure or to spin crossover events. The present results deserve further studies on the electronic properties of these types of compounds for the development of smart materials.

scholarly journals Synthesis and Reactivity of (N2P2)Ni Complexes Stabilized by a Novel Diphosphonite Pyridinophane Ligand

2021 ◽  
Author(s):  
Kei Fuchigami ◽  
Michael B. Watson ◽  
Giang N. Tran ◽  
Nigam P. Rath ◽  
Liviu M. Mirica
Keyword(s):  
Photoelectron Spectroscopy ◽  
Aryl Halide ◽  
Bond Formation ◽  
Cross Coupling ◽  
Electrochemical Studies ◽  
Redox Potentials ◽  
Efficient Catalyst ◽  
X Ray ◽  
Ni Species

A series of (N2P2)Ni<sup>II</sup> complexes (N2P2 = P,P’-ditertbutyl-2,11-diphosphonito[3.3](2,6)pyridinophane) stabilized by a modified tetradentate pyridinophane ligand containing two phosphonite groups were synthesized and characterized. Cyclic voltammetry (CV) studies revealed the accessibility of the Ni<sup>I</sup> oxidation state at moderate redox potentials for these Ni<sup>II</sup> complexes. <i>In situ</i> EPR, low-temperature UV-vis, and electrochemical studies were employed to detect the formation of Ni<sup>I</sup> species during the reduction of Ni<sup>II</sup> precursors. Furthermore, the [(N2P2)Ni<sup>I</sup>(CNtBu)](SbF<sub>6</sub>) complex was isolated upon reduction of the Ni<sup>II</sup> precursor with 1 equiv of CoCp<sub>2</sub>, and was characterized by EPR and X-ray photoelectron spectroscopy (XPS). Finally, the (N2P2)Ni<sup>II</sup>Br<sub>2</sub> complex acts as an efficient catalyst for the Kumada cross-coupling of an aryl halide with an aryl or alkyl Grignard, suggesting that the N2P2 ligand can support the various Ni species involved in the catalytic C-C bond formation reactivity.

scholarly journals Morpholino-Substituted BODIPY Species: Synthesis, Structure and Electrochemical Studies

Crystals ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 36 ◽  
Author(s):  
Hawazen Hassanain ◽  
E. Stephen Davies ◽  
William Lewis ◽  
Deborah L. Kays ◽  
Neil R. Champness
Keyword(s):  
Solid State ◽  
Electronic Properties ◽  
Visible Spectrum ◽  
Methyl Groups ◽  
Electrochemical Studies ◽  
Redox Potentials ◽  
Dye Molecules ◽  
Halogen Bonds ◽  
Uv Visible ◽  
Solid State Structures

Functionalization of 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) chromophores at the 2,6-positions with iodo substituents and morpholino-substituted α-methyl groups affords molecules with strong absorbance in the visible spectrum. The effect of such substitution on the solid-state arrangements, absorption, fluorescence and electronic properties of these dye molecules is reported. The spectroscopic and spectroelectrochemical measurements display intense absorptions in the UV-visible spectrum with bathochromic shifts, in comparison to unfunctionalized BODIPY, and a positive shift in redox potentials due to functionalisation of the BODIPY core. Halogen bonds are observed in the solid-state structures of both halogenated BODIPY species, which in one case leads to the formation of an unusual halogen bonded framework.

Meso-tetrakis(3',5'-di-substituted-phenyl)porphyrins: structural, electrochemical redox and axial ligation properties

2005 ◽  
Vol 09 (06) ◽  
pp. 413-422 ◽  
Author(s):  
Muniappan Sankar ◽  
Puttaiah Bhyrappa ◽  
Babu Varghese ◽  
K. K. Praneeth ◽  
G. Vaijayanthimala
Keyword(s):  
Layer Structure ◽  
Lewis Acidity ◽  
Electrochemical Studies ◽  
Redox Potentials ◽  
Coordinate Structure ◽  
Axial Ligation ◽  
The Core ◽  
Order Of Magnitude ◽  
Electrochemical Redox ◽  
Hammett Parameter

A family of meta octa-substituted 5,10,15,20-tetraphenylporphyrin derivatives and their metal ( Cu(II) and Zn(II) ) complexes were examined by electrochemical studies. These functionalized MTPPs exhibited a dramatic anodic shift (>200 mV ) in their first ring redox potentials relative to the para-phenyl substituted-MTPP(X) complexes and follow a fairly linear relationship with the Hammett parameter of the substituents. The extent of Lewis acidity of the core Zn(II) center in these porphyrins was probed by axial ligation of bases of varying pK a values. The increase in K eq values of the electron deficient Zn(II) porphyrins are as high as an order of magnitude and increase with anodic shift of the electrochemical redox potentials of the porphyrin. A crystal structure of the Zn(II) octa(carboxyethylester phenyl)porphyrin shows six-coordination geometry with the coordination through peripheral ester groups to form a supramolecular two-dimensional layer structure while the ZnT (3',5'- DMP ) P complex exhibited a five-coordinate structure.

scholarly journals Synthesis and Reactivity of (N2P2)Ni Complexes Stabilized by a Novel Diphosphonite Pyridinophane Ligand

2021 ◽  
Author(s):  
Kei Fuchigami ◽  
Michael B. Watson ◽  
Giang N. Tran ◽  
Nigam P. Rath ◽  
Liviu M. Mirica
Keyword(s):  
Photoelectron Spectroscopy ◽  
Aryl Halide ◽  
Bond Formation ◽  
Cross Coupling ◽  
Electrochemical Studies ◽  
Redox Potentials ◽  
Efficient Catalyst ◽  
X Ray ◽  
Ni Species

A series of (N2P2)Ni<sup>II</sup> complexes (N2P2 = P,P’-ditertbutyl-2,11-diphosphonito[3.3](2,6)pyridinophane) stabilized by a modified tetradentate pyridinophane ligand containing two phosphonite groups were synthesized and characterized. Cyclic voltammetry (CV) studies revealed the accessibility of the Ni<sup>I</sup> oxidation state at moderate redox potentials for these Ni<sup>II</sup> complexes. <i>In situ</i> EPR, low-temperature UV-vis, and electrochemical studies were employed to detect the formation of Ni<sup>I</sup> species during the reduction of Ni<sup>II</sup> precursors. Furthermore, the [(N2P2)Ni<sup>I</sup>(CNtBu)](SbF<sub>6</sub>) complex was isolated upon reduction of the Ni<sup>II</sup> precursor with 1 equiv of CoCp<sub>2</sub>, and was characterized by EPR and X-ray photoelectron spectroscopy (XPS). Finally, the (N2P2)Ni<sup>II</sup>Br<sub>2</sub> complex acts as an efficient catalyst for the Kumada cross-coupling of an aryl halide with an aryl or alkyl Grignard, suggesting that the N2P2 ligand can support the various Ni species involved in the catalytic C-C bond formation reactivity.

Effect of Porphyrin Ring Distortion on Redox Potentials of .beta.-Brominated-Pyrrole Iron(III) Tetraphenylporphyrins

1994 ◽  
Vol 33 (23) ◽  
pp. 5169-5170 ◽  
Author(s):  
Karl M. Kadish ◽  
Francis D'Souza ◽  
Anne Villard ◽  
Marie Autret ◽  
Eric Van Caemelbecke ◽  
...  
Keyword(s):  
Porphyrin Ring ◽  
Redox Potentials ◽  
Ring Distortion

scholarly journals Electrochemical Studies of a Truncated Laccase Produced in Pichia pastoris

1999 ◽  
Vol 65 (12) ◽  
pp. 5515-5521 ◽  
Author(s):  
Mirjana Gelo-Pujic ◽  
Hyug-Han Kim ◽  
Nathan G. Butlin ◽  
G. Tayhas R. Palmore
Keyword(s):  
Electron Transfer ◽  
Pichia Pastoris ◽  
Active Site ◽  
Relative Activity ◽  
Cysteine Residue ◽  
Site Directed Mutagenesis ◽  
Electrochemical Studies ◽  
Redox Potentials ◽  
Hydrogen Electrode ◽  
C Terminus

ABSTRACT The cDNA that encodes an isoform of laccase from Trametes versicolor (LCCI), as well as a truncated version (LCCIa), was subcloned and expressed by using the yeast Pichia pastorisas the heterologous host. The amino acid sequence of LCCIa is identical to that of LCCI except that the final 11 amino acids at the C terminus of LCCI are replaced with a single cysteine residue. This modification was introduced for the purpose of improving the kinetics of electron transfer between an electrode and the copper-containing active site of laccase. The two laccases (LCCI and LCCIa) are compared in terms of their relative activity with two substrates that have different redox potentials. Results from electrochemical studies on solutions containing LCCI and LCCIa indicate that the redox potential of the active site of LCCIa is shifted to more negative values (411 mV versus normal hydrogen electrode voltage) than that found in other fungal laccases. In addition, replacing the 11 codons at the C terminus of the laccase gene with a single cysteine codon (i.e., LCCI→LCCIa) influences the rate of heterogeneous electron transfer between an electrode and the copper-containing active site (k het for LCCIa = 1.3 × 10−4 cm s−1). These results demonstrate for the first time that the rate of electron transfer between an oxidoreductase and an electrode can be enhanced by changes to the primary structure of a protein via site-directed mutagenesis.

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