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Mechanistic aspects of ligand substitution on [(H 2 O)(tap) 2 RuORu(tap) 2 (H 2 O)] 2+ ion {tap = 2‐( m ‐tolylazo)pyridine} by some amino acids in aqueous medium at physiological pH
Author(s) -
Mandal Arup,
Mondal Subala,
Karmakar Parnajyoti,
Mallick Subhasis,
Bera Biplab K.,
Ghosh Alak K.
Publication year - 2012
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.20701
Subject(s) - chemistry , ligand (biochemistry) , reaction rate constant , outer sphere electron transfer , equilibrium constant , glycine , stereochemistry , aqueous solution , ion , crystallography , analytical chemistry (journal) , amino acid , kinetics , organic chemistry , biochemistry , physics , quantum mechanics , receptor
The interaction of the title complex with selected amino acids such as glycine (L 1 H), l ‐valine (L 2 H), and l ‐leucine (L 3 H) has been studied spectrophotometrically in aqueous medium as a function of [substrate complex], [ligand], and temperature. The reaction has been monitored at 600 nm, where the spectral difference between the reactant and product is maximum. At pH 7.4, the reaction has been found to proceed via two distinct consecutive steps, i.e., it shows a nonlinear dependence on the concentration of ligands: The first process is [ligand] dependent, but the second step is [ligand] independent. The rate constants for the processes are k 1 ∼10 −3 s −1 and k 2 ∼10 −4 s −1 . The activation parameters were calculated from Eyring plots. Based on the kinetic and activation parameters, an associative interchange mechanism is proposed for the interaction processes. From the temperature dependence of the outer sphere association equilibrium constant, the thermodynamic parameters were also calculated, which gives a negative Δ G o value for both the steps at all temperatures studied, supporting the spontaneous formation of an outer sphere association complex. The product of the reaction has been characterized with the help of conductance measurement, IR, NMR, and ESI‐mass spectroscopic analysis. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 612–623, 2012