scholarly journals The photo-physical study of the interaction of riboflavin with Nicotine in bicontinuous microemulsion

2017 ◽  
Vol 6 (6) ◽  
pp. 267-275
Author(s):  
Maurice Ohaekeleihem Iwunze
Keyword(s):  
Electron Transfer ◽  
Free Energy ◽  
Rate Constant ◽  
Reorganization Energy ◽  
Outer Sphere ◽  
Electron Transfer Reaction ◽  
Microemulsion System ◽  
Quenching Rate ◽  
Bicontinuous Microemulsion ◽  
Bimolecular Quenching

Steady-state fluorescence spectroscopy was used to study the interaction of riboflavin with nicotine in a bicontinuous microemulsion system made up of 42.11:13.70:21.34:22.85 % w/w of water: oil: surfactant: cosurfactant. The surfactant used is cetyltrimethylammonium bromide (CTAB), the oil is tetradecane and the cosurfactant is 1-pentanol. It is observed that the interaction of riboflavin and nicotine in the prepared microemulsion lead to the quenching of riboflavin fluorescence. The bimolecular quenching rate constant, kq, of riboflavin by nicotine was observed as 4.15 x 109 M-1 s -1 with an efficiency of 56 %. The mechanism of the reaction is proposed to be diffusion limited in an activated electron transfer reaction in a solvent separated (outer-sphere) scheme. The electron transfer rate constant, kET, was calculated as 5.89 x 109 s -1 with an activation rate constant, ka, of 9.52 x 109 s -1 . The calculated solvent reorganization energy, λs, of the reaction was 1.09 eV, the free energy of interaction, ΔGo , is -2.9 eV and the free energy of activation, ΔG*, was calculated as 0.75 eV.

scholarly journals Studies on the Photoinduced Interaction between Zn(II) Porphyrin and Colloidal TiO2

2010 ◽  
Vol 2010 ◽  
pp. 1-5 ◽  
Author(s):  
Heyong Huang ◽  
Jiahong Zhou ◽  
Yan Zhou ◽  
Yanhuai Zhou ◽  
Yuying Feng
Keyword(s):  
Electron Transfer ◽  
Free Energy ◽  
Rate Constant ◽  
Reduction Potential ◽  
Fluorescence Emission ◽  
Quenching Mechanism ◽  
Quenching Rate ◽  
Absorption And Fluorescence Spectroscopy ◽  
Nanoparticle Surface ◽  
Quenching Rate Constant

The interaction of Zn(II) porphyrin (ZnPP) with colloidal TiO2was studied by absorption and fluorescence spectroscopy. The fluorescence emission of ZnPP was quenched by colloidal TiO2upon excitation of its absorption band. The quenching rate constant (kq) is1.24×1011 M−1 s−1. These data indicate that there is an interaction between ZnPP and colloidal TiO2nanoparticle surface. The quenching mechanism is discussed on the basis of the quenching rate constant as well as the reduction potential of the colloidal TiO2. And the mechanism of electron transfer has been confirmed by the calculation of free energy change(ΔGet)by applying Rehm-Weller equation as well as energy level diagram.

scholarly journals Study of Electron Transfer between Amines and Biologically Active 4 - Aryloxymethylcoumarin

2016 ◽  
Vol 15 (1) ◽  
pp. 29-45
Author(s):  
U P Raghavendra
Keyword(s):  
Electron Transfer ◽  
Free Energy ◽  
Aromatic Amines ◽  
Reduction Potential ◽  
Standard Free Energy ◽  
Reorganization Energy ◽  
Biologically Active ◽  
Rate Parameter ◽  
Quenching Rate ◽  
Electron Transfer Theory

Electron transfer from aliphatic and aromatic amines to biologically    active    4-aryloxymethyl    coumarin1-(4- iodophenoxymethyl)-benzo[ f ]coumarin (1IPMBC)    has been investigated in acetonitrile solvent. The variation of quenching rate parameter with reduction potential of amines indicates the electron transfer from amines to investigated      coumarin molecule.Experimentally determined values of quenching rate parameter k q are well correlated with the standard free energy changes ( ∆G 0 ) within the framework of Marcus electron transfer theory. In the investigatedsystems,solvent reorganization energy appears to play a major role in governing electron transfer dynamics.

Synthesis, CMC Determination, and Outer Sphere Electron Transfer Reaction of the Surfactant–Complex Ion, cis-[Co(en)2(4CNP)(DA)]3+ with [Fe(CN)6]4– in Micelles, β-cyclodextrin, and Liposome (Dipalmidoylphosphotidylcholine) Vesicles

2013 ◽  
Vol 66 (8) ◽  
pp. 930 ◽  
Author(s):  
Karuppiah Nagaraj ◽  
Sankaralingam Arunachalam
Keyword(s):  
Electron Transfer ◽  
Rate Constant ◽  
Transfer Reaction ◽  
Hydrophobic Effect ◽  
Outer Sphere ◽  
Electron Transfer Reaction ◽  
Pyridine Ligand ◽  
Physico Chemical ◽  
Different Temperatures ◽  
Outer Sphere Electron Transfer

The surfactant cobalt(iii) complex, cis-[Co(en)2(4CNP)(DA)](ClO4)3, en = ethylenediamine, 4CNP = 4-cyanopyridine, DA = dodecylamine, was synthesized and characterized by physico-chemical and spectroscopic methods. The critical micelle concentration value of this complex was obtained from the conductivity measurements at different temperatures to evaluate, ΔGm0, ΔHm0, and ΔSm0. The kinetics of outer sphere electron transfer reaction of this complex with Fe(CN)64– ion in micelles, β-cyclodextrin as well as in liposome vesicles media were studied. The rate constant increases with increase in the concentration of micelles but decreases in presence of β-cyclodextrin, which is a good structure breaker of micelles. In liposome vesicles media the rate constant is different at below and above phase transition temperature. The results have been explained based on the hydrophobic effect, the presence of pyridine ligand containing 4-cyano substituent and the reactants with opposite charge.

Kinetics of N-substituted phenothiazines and N-substituted phenoxazines oxidation catalyzed by fungal laccases

2009 ◽  
Vol 4 (1) ◽  
pp. 62-67 ◽  
Author(s):  
Lidija Tetianec ◽  
Juozas Kulys
Keyword(s):  
Electron Transfer ◽  
Redox Potential ◽  
Reorganization Energy ◽  
Outer Sphere ◽  
Initial Reaction Rate ◽  
Initial Reaction ◽  
Type I ◽  
Electron Transfer Mechanism ◽  
Recombinant Laccase ◽  
Kinetics Of

AbstractLaccase-catalyzed oxidation of N-substituted phenothiazines and N-substituted phenoxazines was investigated at pH 5.5 and 25°C. The recombinant laccase from Polyporus pinsitus (rPpL) and the laccase from Myceliophthora thermophila (rMtL) were used. The dependence of initial reaction rate on substrate concentration was analyzed by applying the laccase action scheme in which the laccase native intermediate (NI) reacts with a substrate forming reduced enzyme. The reduced laccase produces peroxide intermediate (PI) which in turn decays to the NI. The calculated constant (kox) values of the PI formation are (6.1±3.1)×105 M−1s−1 for rPpL and (2.5±0.9)×104 M−1s−1 for rMtL. The bimolecular constants of the reaction of the native intermediate with electron donor (kred) vary in the interval from 2.2×105 to 2.1×107 M−1s−1 for rPpL and from 1.3×102 to 1.8×105 M-1s−1 for rMtL. The larger reactivity of rPpL in comparison to rMtL is associated with the higher redox potential of type I Cu of rPpL. The variation of kred values for both laccases correlates with the change of the redox potential of substrates. Following outer sphere (Marcus) electron transfer mechanism the calculated activationless electron transfer rate and the apparent reorganization energy are 5.0×107 M−1s−1 and 0.29 eV, respectively.

Electron transfer reactions of nickel complexes of 1,4,7-triazacyclodecane

1985 ◽  
Vol 63 (11) ◽  
pp. 2983-2989 ◽  
Author(s):  
M. G. Fairbank ◽  
A. McAuley ◽  
P. R. Norman ◽  
O. Olubuyide
Keyword(s):  
Electron Transfer ◽  
Exchange Rate ◽  
Proton Transfer ◽  
Electrochemical Oxidation ◽  
Rate Constant ◽  
Aqueous Media ◽  
Nickel Complexes ◽  
Outer Sphere ◽  
The Self ◽  
Transfer Reactions

The preparation of [Ni(1,4,7-triazacyciodecane)2]3+, (Ni(10-aneN3)23+) is described. The existing procedure has been modified leading to good yields of the ligand trihydrochloride. The nickel(II) analogue (reported previously) is oxidised in a facile manner, either by Co3+aq in acidic aqueous media or by NO+ in CH3CN. Since the octahedral NiN6, chromophore is retained upon electron transfer, outer sphere reactions both of the Ni(II) and Ni(III) species have been studied. Rates of oxidation by various nickel(III) macrocycles have been measured and details are provided. Electrochemical oxidation of the Ni(II) complex is consistent with E0(Ni(10-aneN3)23+/2+) = 0.997 V (vs. NHE). The data have been used in a Marcus correlation, leading to the self-exchange rate k11 for the couple (Ni(10-aneN3)23+/2+) = (2 ± 1) × 104 M−1 s−1. This value is compared with other data derived using octahedral Ni(II)/Ni(III) centres. The oxidation of the Ni(II) complex by Co(III)aq has been studied in both protonated and deuterated media. There is no evidence for any proton transfer (from the N—H) being coupled to the electron transfer step. The observed rate constant for the reaction of Co3+ with Ni(II)(10-aneN3)22+ (550 M−1 s−1) may be compared with the calculated outer sphere rate (270 M−1 s−1). An estimate of k11 (CoOH2+/+) ~ 3 M−1 s−1 for the CoOH2+/+ exchange is discussed.

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