Comparative Study of Micellar and DNA Effects on the Reaction [Ru(NH₃)₅py]²⁺ + S₂O₈^2-

Abstract

The kinetics of the electron-transfer reaction between pentaamminepyridine ruthenium (II) perchlorate, [Ru(NH3)5py](ClO4)2, and sodium peroxodisulfate, Na2S2O8, was studied in DNA and SDS micellar solutions. The results can be interpreted by taking as a starting point the pseudophase model. However, the model must be modified according to the characteristics of the reaction media. Thus, the binding of the substrate (the ruthenium complex) to DNA is anticooperative in character, in such a way that the binding constant increases as the [DNA]/[Ru(NH3)5py] 2+ ratio increases. On the other hand, the binding of the ruthenium complex to SDS micelles decreases as the [SDS]/[Ru(NH3)5py] 2+ ratio increases as a consequence of the changes of the surface potential of the micelles.

Method for the Evaluation of the Reorganization Energy of Electron Transfer Reactions Produced under Restricted Geometry Conditions

“…Table contains the kinetic data corresponding to the three electron transfer reactions. The data corresponding to [Ru(NH 3 ) 5 py] 2+ in Table were taken from ref .…”

“…Kinetics Measurements. Kinetic runs corresponding to the complexes with pz and 4-CNpy as ligands were carried out as described in ref for L = py. The concentration of the reactants in the reaction mixture were the same as in ref : [Ru(NH 3 ) 5 L] 2+ = 2 × 10 -5 mol dm -3 and [S 2 O 8 ] 2- = 1.5 × 10 -4 mol dm -3 .…”

“…Kinetic runs corresponding to the complexes with pz and 4-CNpy as ligands were carried out as described in ref for L = py. The concentration of the reactants in the reaction mixture were the same as in ref : [Ru(NH 3 ) 5 L] 2+ = 2 × 10 -5 mol dm -3 and [S 2 O 8 ] 2- = 1.5 × 10 -4 mol dm -3 . Pseudo-first-order rate constants were obtained from the slopes of the linear plots of ln( A t − A ∞ ) versus time, where A t and A ∞ are the absorbances at time t and when the reaction is finished, respectively.…”

Quantification of salts and cosolvents–DNA interactions in terms of free energies: A study using the pyren-1-carboxyaldehyde as fluorescent probe

“…These variations of DG corr max can be explained by using a model of two states: assuming that the cations of salts directly interact with DNA, causing a structural change in the DNA, two kinds of DNA will be in the solution, free and bound to the cation of the salt, with different capacities to bind pyrene. It must be remarked that the binding of the pyrene to the DNA in the presence of salt is anti-cooperative in nature, according to the results obtained in previous studies about the influence of DNA in the reactivity of cationic ligands [23][24][25]. It should be noted that, as the salt concentration increases, the anti-cooperative nature of the pyrene binding decreases, and becomes non-cooperative, which is also in agreement with previous works [23,26].…”

Kinetics and Thermodynamics of Formation and Electron‐Transfer Reactions of Surfactant Cobalt(III) Complexes Containing Polypyridyl Ligands with Fe(CN)64−in Microheterogeneous Environment

“…It is well known that several redox reactions in micellar media were influenced by the hydrophobic and electrostatic forces, and, for a given set of reactions, the observed rate depends on the extent of association between the reactants and micellar aggregates . Numerous reports are available on the reaction between Fe(CN) 6 4− and metal complexes . Gaswick and Haim have reported that the hexacyanoferrate(II) anion can reduce pentamminecobalt(III) complexes to cobalt(II) via an outer‐sphere electron‐transfer step , and they have also reported that the substituted pentamminecobalt(III) complexes could be reduced by hexacyanoferrate(II) with the formation of an ion pair.…”