Kinetic Studies on the Electron Transfer between Azide and Nickel(IV) Oxime Imine Complexes in Aqueous Solution

1996 ◽  
Vol 69 (12) ◽  
pp. 3475-3482 ◽  
Author(s):  
Santanu Bhattacharya ◽  
Pradyot Banerjee
Keyword(s):  
Aqueous Solution ◽  
Electron Transfer ◽  
Kinetic Studies

New low-spin Co(II) complexes with novel tripodal 1,1,1-tris(dimethylphosphinomethyl)ethane ligand: electron transfer kinetics and spectroscopic characterization of Co(II)P6 and Co(II)P3S3 ions in aqueous solution

2001 ◽  
Vol 79 (9) ◽  
pp. 1344-1351 ◽  
Author(s):  
Satoshi Iwatsuki ◽  
Kenji Obeyama ◽  
Nobuyoshi Koshino ◽  
Shigenobu Funahashi ◽  
Kazuo Kashiwabara ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Electron Transfer ◽  
Spin State ◽  
Kinetic Studies ◽  
Spectroscopic Characterization ◽  
Electronic Configuration ◽  
Exchange Reactions ◽  
Teller Distortion ◽  
Jahn Teller ◽  
Controlled Potential

Substitution-inert Co(II) complexes with tripodal 1,1,1-tris(dimethylphosphinomethyl)ethane were produced in aqueous solution by the controlled-potential electrolysis. EPR studies indicated that the Co(II)P6 and Co(II)P3S3 species are in the low-spin t62ge1g state. The analyses of the absorption spectra of the Co(II) species in solution indicated significant Jahn–Teller distortion in Co(II)P6 and Co(II)P3S3 ions as expected for the low-spin d7 electronic configuration, while less distortion was observed for the Co(II)S6 ion. Kinetic studies of the redox reactions involving these Co(III/II) species confirmed that the electron self-exchange reactions for the Co(III/II)P6 and Co(III/II)P3S3 couples are relatively fast (kex ~ 1 × 104 dm3 mol–1 s–1), which is consistent with the results for other low-spin – low-spin Co(III/II) couples. It was concluded that the nephelauxetic effect of the P-donor atom stabilizes the low-spin state in Co(II), and that the rather rapid electron exchange rates for these Co(III/II) couples were explained by the lack of the spin reorganization process required for the ordinary low-spin – high-spin Co(III/II) couples.Key words: cobalt(III/II), spin state, EPR study, kinetics, electron transfer.

Flavin radicals, conformational sampling and robust design principles in interprotein electron transfer: the trimethylamine dehydrogenase-electron-transferring flavoprotein complex

2004 ◽  
Vol 71 ◽  
pp. 1-14
Author(s):  
David Leys ◽  
Jaswir Basran ◽  
François Talfournier ◽  
Kamaldeep K. Chohan ◽  
Andrew W. Munro ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Kinetic Studies ◽  
Molecular Assembly ◽  
Conformational Sampling ◽  
Trimethylamine Dehydrogenase ◽  
Key Residues ◽  
Electron Transferring Flavoprotein ◽  
Electron Transfer Complex

TMADH (trimethylamine dehydrogenase) is a complex iron-sulphur flavoprotein that forms a soluble electron-transfer complex with ETF (electron-transferring flavoprotein). The mechanism of electron transfer between TMADH and ETF has been studied using stopped-flow kinetic and mutagenesis methods, and more recently by X-ray crystallography. Potentiometric methods have also been used to identify key residues involved in the stabilization of the flavin radical semiquinone species in ETF. These studies have demonstrated a key role for 'conformational sampling' in the electron-transfer complex, facilitated by two-site contact of ETF with TMADH. Exploration of three-dimensional space in the complex allows the FAD of ETF to find conformations compatible with enhanced electronic coupling with the 4Fe-4S centre of TMADH. This mechanism of electron transfer provides for a more robust and accessible design principle for interprotein electron transfer compared with simpler models that invoke the collision of redox partners followed by electron transfer. The structure of the TMADH-ETF complex confirms the role of key residues in electron transfer and molecular assembly, originally suggested from detailed kinetic studies in wild-type and mutant complexes, and from molecular modelling.

Micellar catalysis of organic reactions. VIII. Kinetic studies of the hydrolysis of 2-acetyloxybenzoic acid (aspirin) in the presence of micelles

1982 ◽  
Vol 35 (7) ◽  
pp. 1357 ◽  
Author(s):  
TJ Broxton
Keyword(s):  
Aqueous Solution ◽  
Cetyltrimethylammonium Bromide ◽  
Cetylpyridinium Chloride ◽  
Kinetic Studies ◽  
Base Catalysis ◽  
Plateau Region ◽  
General Base ◽  
Mechanism Of Hydrolysis ◽  
Ph Range ◽  
Hydrolysis Of

The hydrolysis of 2-acetyloxybenzoic acid in the pH range 6-12 has been studied in the presence of micelles of cetyltrimethylammonium bromide (ctab) and cetylpyridinium chloride (cpc). In the plateau region (pH 6-8) the hydrolysis is inhibited by the presence of micelles, while in the region where the normal BAC2 hydrolysis (pH > 9) occurs the reaction is catalysed by micelles of ctab and cpc. The mechanism of hydrolysis in the plateau region is shown to involve general base catalysis by the adjacent ionized carboxy group both in the presence and absence of micelles. This reaction is inhibited in the presence of micelles because the substrate molecules are solubilized into the micelle and water is less available in this environment than in normal aqueous solution.

A New Approach to Fluorescent Chemosensor of Cu2+ Ion

2014 ◽  
Vol 513-517 ◽  
pp. 65-69
Author(s):  
Xiao Jun Hu ◽  
Xin Yan Hu ◽  
Zhi Zhang
Keyword(s):  
Aqueous Solution ◽  
Electron Transfer ◽  
Self Assembly ◽  
Ph Value ◽  
Sodium Dodecyl ◽  
Fluorescence Emission ◽  
Fluorescent Chemosensor ◽  
Dynamic Quenching ◽  
Transfer Effects ◽  
New Approach

According to the principle of dynamic quenching a new ON-OFF fluorescent chemosensor for Cu2+ions was designed, this chemosensor was composed of p-tert-butylthiacalix [arene (TCA),sodium dodecyl sulfate (SDS) and perylene through the form of self-assembly in aqueous solution. Addition of Cu2+ions could result in a quenching of the fluorescence emission of perylene inside micelles, which due to intramicellar complex-fluorophore electron-transfer or energy-transfer effects induced by the complexation of TCA with the Cu2+ions.The experimental results indicated that: Under the condition of TCA/perylene was 800/1, SDS concentration was 150mmol/L and pH value above 9, according to the fluorescence quenching ,within a certain range of the concentration of Cu2+ion can be linearly determined.

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