Kinetic and mechanistic studies on the interaction between glycylglycine and <Emphasis Type="Italic">cis</Emphasis>-diaqua-<Emphasis Type="Italic">bis</Emphasis>-(bipyridine)-ruthenium(II) complex in aqueous medium

The kinetics of interaction between glycylglycine and cis-[Ru(bipy)₂(H₂O)₂]²⁺ have been studied spectrophotometrically as a function of [Ru(bipy)₂(H₂O) ₂ ²⁺ ], [diglycine] and temperature at a particular pH (4.8), where the substrate complex exists predominantly as the diaqua species and diglycine as the zwitter ion. The reaction has been found to proceed via two consecutive steps. The first step involves the ligand-assisted anation, while the second step involves chelation when the second aqua ligand is displaced. Rate constants have been evaluated and activation parameters calculated. The low enthalpy of activation and large negative values of entropy of activation indicate an associative mode of activation for both steps.     

A Kinetic and Mechanistic Study on Substitution of Aqua Ligands from <Emphasis Type="Italic">cis</Emphasis>-diaqua-<Emphasis Type="Italic">bis</Emphasis>-(bipyridyl)-ruthenium(II) Complex by Thiosemicarbazide in Aqueous Medium

The kinetics of the interaction of thiosemicarbazide with cis-[Ru(bipy)₂(H₂O)₂]²⁺ (bipy = α α′-bipyridyl) have been studied spectrophotometrically as a function of [Ru(bipy)₂(H₂O)₂²⁺], [bipyridyl] and temperature, at a particular pH (4.8), where the substrate complex exists predominantly as the diaqua species and thiosemicarbazide as the neutral ligand. The reaction proceeds via an outer sphere association complex formation, followed by two slow consecutive steps. The first is the conversion of the aforementioned complex into the inner sphere complex, and the second step involves the entrance of another thiosemicarbazide molecule in the coordination zone of Ru(II) whereby, in each step, an aqua ligand is replaced. The association equilibrium constant (K_E) for the outer sphere complex formation has been evaluated together with rate constants for the two subsequent steps. Activation parameters have been calculated for both steps using the Eyring equation (ΔH₁^# = 25.37±1.6 kJ mol⁻¹, ΔS₁^# = −215.48 ± 4.5 J K⁻¹ mol⁻¹, ΔH₂^# = 24.24 ± 1.1 kJ mol⁻¹, ΔS₂^# = −207.14 ± 3.0 J K⁻¹ mol⁻¹). The low enthalpy of activation and large negative value of entropy of activation indicate an associative mode of activation for both aqua ligand substitution processes. From the temperature dependence of K_E, the thermodynamic parameters calculated are: ΔH⁰ = 10.75±0.54 kJ mol⁻¹ and ΔS⁰ = 84.67 ± 1.75 J K⁻¹ mol⁻¹, which give a negative ΔG⁰ value at all temperatures studied, supporting the spontaneous formation of an outersphere association complex prior to the first step.     

Kinetics and mechanism of aqua ligand substitution from cis-diaqua(cis-1,2-diaminocyclohexane)platinum(II)perchlorate by diethyldithiocarbamate anion in aqueous medium

The kinetics of the interaction of diethyldithiocarbamate (Et₂DTC) with [Pt(dach)(H₂O)₂]²⁺ (dach = cis-1,2-diaminocyclohexane) have been studied spectrophotometrically as a function of [Pt(dach)(H₂O)₂ ²⁺], [Et₂DTC] and temperature at a particular pH (4.0). The reaction proceeds via rapid outer sphere association complex formation followed by two slow consecutive steps. The first step involves the transformation of the outer sphere complex into an inner sphere complex containing a Pt–S bond and one aqua ligand, while the second step involves chelation when the second aqua ligand is replaced. The association equilibrium constant K _E and two rate constants k ₁ and k ₂ have been evaluated. Activation parameters for both the steps have been calculated (∆H ₁ ^# = 66.8 ± 3.7 kJ mol⁻¹, ∆S ₁^# = −81 ± 12 JK⁻¹ mol⁻¹ and ∆H ₂^# = 95.1 ± 2.8 kJ mol⁻¹, ∆S ₂^# = −34.4 ± 9.1 JK⁻¹ mol⁻¹). The low enthalpy of activation and negative entropy of activation indicate an associative mode of activation for both the steps.     

Mechanistic aspects of ligand substitution on [(H2O)(tap)2RuORu(tap)2(H2O)]2+ ion {tap = 2‐(m‐tolylazo)pyridine} by some amino acids in aqueous medium at physiological pH

The interaction of the title complex with selected amino acids such as glycine (L¹H), l ‐valine (L²H), and l ‐leucine (L³H) 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 k₁～10^?3 s^?1 and k₂～10^?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     

The Reactivity of vic-dioximes Towards the [(H2O)(tap)2RuORu(tap)2(H2O)]2+ Ion {tap = 2-(m-tolylazo)pyridine} at Physiological pH

Kinetics of aqua ligand substitution from [(H₂O)(tap)₂RuORu(tap)₂(H₂O)]²⁺ {tap = 2-(m-tolylazo)pyridine}, by three vicinal dioximes, namely dimethylglyoxime (L¹H), 1,2-cyclohexanedione dioxime (L²H) and α-furil dioxime (L³H), have been studied spectrophotometrically in the 35–50 °C temperature range. The reaction was monitored at 560 nm where the absorbance between the reactant and product is at a maximum. At pH 7.4, the reaction has been found to proceed via two distinct consecutive steps, i.e., it shows a non-linear 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, calculated from Eyring plots, suggest an associative mechanism for the interaction process. From the temperature dependence of the outer sphere association equilibrium constants, the thermodynamic parameters were also calculated, which give negative ΔG° values 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 IR and ESI-mass spectroscopic analysis.     

Substitution of aqua ligands from cis‐[Pt(en)(H2O)2](ClO4)2 and cis‐[Pt(dmen)(H2O)2](ClO4)2 (en = ethylenediamine,dmen = N N′‐dimethyl ethylenediamine) by glycine in aqueous medium—a kinetic and mechanistic approach

The kinetics of the interaction of glycine with cis‐[Pt(en)(H₂O)₂](ClO₄)₂ and cis‐[Pt(dmen)(H₂O)₂](ClO₄)₂ (en = ethylenediamine, dmen = N,N′‐dimethylethylene‐diamine) have been studied spectrophotometrically as a function of [substrate complex], [glycine], and temperature at a particular pH (4.0) where the substrate complex exists predominantly as the diaqua species and glycine as the zwitterion. The reaction was found to proceed through two consecutive steps. The first step involves the ligand‐assisted anation, while the second step involves chelation when the second aqua ligand is displaced. Rate constants have been evaluated using the Weyh and Hamm method. Activation parameters for both steps have also been calculated using the Eyring equation. The low enthalpy of activation and large negative values of entropy of activation indicate an associative mode of activation for both steps. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 489–495, 2005     

Kinetics and mechanism of biphasic substitution reactions of a platinum(II) complex with thioglycollic acid and 4-methyl-3-thiosemicarbazide in aqueous solution

The kinetics of interactions between cis-diaqua(2-aminomethylpyridine)platinum(II) perchlorate (1) [Pt(pic)(OH₂)₂](ClO₄)₂, thioglycollic acid (TGA), and 4-methyl-3-thiosemicarbazide (MTSC) have been studied spectrophotometrically in aqueous medium as a function of the [complex (1)] as well as [TGA] or [MTSC], pH and temperature at constant ionic strength. The observed pseudo-first-order rate constants were proportional to [TGA] or [MTSC]. At pH 4.0, the interactions of (1) with both TGA and MTSC show two distinct consecutive steps; the first step is dependent and second independent of [TGA] or [MTSC]. The association equilibrium constant (K _E) for the outer sphere complex formation has been evaluated, along with the rate constants for the two steps. The first step is assigned to ligand-assisted anation and the second to chelation of TGA or MTSC. The activation parameters for both the steps were evaluated using Eyring’s equation. On the basis of the kinetic observations and evaluated activation parameters, an associative mechanism is proposed for both the reactions.     

Kinetics of substitution of aqua ligands from cis-diaqua(ethylenediamine)platinum(II) perchlorate by DL-penicillamine in aqueous medium

The kinetics of the interaction of DL-penicillamine with [Pt(en)(H₂O)₂]²⁺ have been studied spectrophotometrically as a function of [Pt(en)(H₂O)₂]²⁺, [DL-penicillamine] and temperature at pH 4.0. The reaction proceeds via rapid outer sphere association complex formation, followed by two slow consecutive steps. The first is the conversion of the aforementioned complex into the inner sphere complex and the second is the slower chelation step whereby another aqua ligand is replaced. The association equilibrium constant (K _E) for the outer sphere complex formation has been evaluated together with rate constants for the two subsequent steps. Activation parameters have been calculated for both steps using the Eyring equation (H ₁ = 46.5 ± 5.0 kJ mol^–1, S ₁ = – 143.0 ± 15.0 J K^–1 mol^–1, H ₂ = 44.3 ± 1.3 kJ mol^–1, S ₂ = –189.0 ± 4.2 J K^–1 mol^–1). The low enthalpy of activation and large negative entropy of activation values indicate an associative mode of activation for both aqua ligand substitution processes.     

Kinetics and mechanism of interaction of Pt(II) complex with bio-active ligands and in vitro Pt(II)-sulfur adduct formation in aqueous medium: bio-activity and computational study

Kinetics of interaction between [Pt(pic)(H₂O)₂](ClO₄)₂, 2 (where pic = 2-aminomethylpyridine) with the selected ligands DL-methionine (DL-meth) and DL-penicillamine (DL-pen) have been studied spectrophotometrically in aqueous medium separately as a function of [2] as well as [ligand], pH and temperature at constant ionic strength. The association equilibrium constants (K_E) for the outer sphere complex formation have been evaluated together with the rate constants for the two subsequent steps. Activation parameters (enthalpy of activation ΔH^≠ and entropy of activation ΔS^≠) were calculated from the Eyring equation. An associative mechanism of substitution is proposed for both reactions on the basis of the kinetic observations, evaluated activation parameters, and spectroscopic data. Structural optimizations, HOMO-LUMO energy calculation, and Natural Bond Orbital (NBO) analysis of 2–4 were carried out with Density Functional Theory. Bonding mode of thiol and thio-ether is confirmed by spectroscopic analyses and NBO calculation. Cytotoxic properties of 2–4 were explored on A549 carcinoma cell lines; DNA-binding properties of the complexes were also investigated by gel electrophoresis.     

Kinetics and Mechanism of the Interaction of Di-μ-hydroxobis(1,10-phenanthroline)dipalladium(II) Perchlorate with Thioglycolic Acid and Glutathione in Aqueous Solution

The kinetics of interaction between di-μ-hydroxobis(1,10-phenanthroline)dipalladium(II) perchlorate and thioglycolic acid and with glutathione has been studied spectrophotometrically in aqueous medium as a function of the complex concentration as well as the ligand concentrations, pH, and temperature at constant ionic strength. The observed pseudo-first-order rate constants k _obs (s^?1) obeyed the equation k _obs = k ₁[Nu] (Nu = nucleophile). At pH = 6.5, the interaction with thioglycolic acid shows two distinct consecutive steps and both steps are dependent on the concentration of thioglycolic acid. The rate constants for the process are: k ₁ ≈ 10^?5 s^?1 and k ₂ ≈ 10^?3 dm³ · mol^?1 · s^?1. The association equilibrium constant (K _E) for the outer sphere complex formation has been evaluated together with the rate constants for the two subsequent steps. The other bio-active ligand, glutathione, showed a single step reaction depending on [ligand] with a second-order anation rate constant: the 10² (k ₂) values are (61.72, 79.20, 109.24 and 154.33) dm³ · mol^?1 · s^?1 at 20, 25, 30 and 35 °C, respectively. On the basis of the kinetic observations and evaluated activation parameters, plausible associative mechanisms are proposed for both interaction processes.     

Kinetic study of the interaction of three glycine‐containing dipeptides with diaquaethylenediamineplatinum(II) in aqueous medium

The kinetics of the interaction of three glycine‐containing dipeptides, namely, glycine‐L‐leucine (Gly‐Leu), glycine‐L‐isoleucine (Gly‐Ile), and glycine‐valine (Gly‐Val) with [Pt(en)(H₂O)₂](ClO₄)₂ has been studied spectrophotometrically as a function of [substrate complex], [dipeptides] and temperature at a particular pH(4.0), where the substrate complex exists predominantly as the diaqua species and the dipeptides as a zwitterion. The substitution reaction shows two consecutive steps; the first is the ligand‐assisted anation and the second is the chelation step. The activation parameters for both the steps were evaluated using Eyring's equation. The low ΔH₁^≠ and large negative value of ΔS₁^≠ as well as ΔH₂^≠ and ΔS₂^≠ indicate an associative mode of activation for both the aqua ligand substitution processes. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 498–506, 2011     

Quantitative study of the quasiequilibrium in the system (hydroxo)oxo-(5,10,15,20-tetraphenylporphynato)-molybdenum(V)-piperidine in toluene medium

The quasiequilibrium interaction of (hydroxo)oxo-(5,10,15,20-tetraphenylporphynato)molybdenum(V) and piperidine in the toluene medium has been studied by means of chemical kinetics and spectrophotometric titration. It has been revealed that the molecular complex formation proceeds as slow irreversible salt formation reaction. It is preceded by the stages of equilibrium substitution of the hydroxo group OH-with piperidine, the outer sphere cationic complex formation [K ₁ (2.03±0.28)×10³ M^?1]; and by the coordination of the second piperidine molecule to the cationic complex (K ₂ 1.76±0.39 M^?1). The complex formation has been completely kinetically described: the rate equations and rate constants have been derived, and the rate limiting stage has been identified. In addition, the physicochemical data on the intermediates and products are presented. The prospects of application of the mixed porphyrin-containing complex as piperidine receptor, alkaloids and pharmaceuticals building block, have been justified.     

Hydroxypalladation Precedes the Rate‐Determining Step in the Wacker Oxidation of Ethene

The complete reaction mechanism and kinetics of the Wacker oxidation of ethene in water under low [Cl^?], [Pd^II], and [Cu^II] conditions are investigated in this work by using ab initio molecular dynamics. These extensive simulations shed light on the molecular details of the associated individual steps, along two different reaction routes, starting from a series of ligand‐exchange processes in the catalyst precursor PdCl₄^2? to the final aldehyde‐formation step and the reduction of Pd^II. Herein, we report that hydroxylpalladation is not the rate‐determining step and is, in fact, in equilibrium. The newly proposed rate‐determining step involves isomerization and follows the hydroxypalladation step. The mechanism proposed herein is shown to be in excellent agreement with the experimentally observed rate law and rate. Moreover, this mechanism is in consensus with the observed kinetic isotope effects. This report further confirms the outer‐sphere (anti) hydroxypalladation mechanism. Our calculations also ratify that the final product formation proceeds through a reductive elimination, assisted by solvent molecules, rather than through β‐hydride elimination.     

Equilibrium and <Superscript>1</Superscript>H NMR Kinetic Study of the Reactions of Dichlorido [S-Methyl-L-Cysteine(N,S)]Platinum(II) Complex with Some Relevant Biomolecules

The formation equilibria of the [Pt(SMC)(H₂O)₂]⁺ complex with some biologically relevant ligands such as L-methionine (L-met) and glutathione (GSH) were studied. The stoichiometry and stability constants of the formed complexes are reported, and the concentration distribution of the various complex species has been evaluated as a function of pH. The reaction between [PtCl₂(SMC)] and guanosine-5′-monophosphate (5′-GMP) was studied by ¹H NMR spectroscopy. The NMR spectra indicated that first step is the hydrolysis of the [PtCl₂(SMC)] complex and second step is the substitution of an aqua ligand, either in the cis or trans position with guanosine-5′-monophosphate in molar ratio 1:1. The values of rate constant showed faster substitution of coordinated H₂O in the trans position to the S donor atom of S-methyl-L-cysteine, whereas the slower reaction was assigned to the displacement of the cis coordinated aqua molecule. This is due to the strong trans labilization effect of coordinated sulfur. Electronic Supplementary Material  The online version of this article () contains supplementary material, which is available to authorized users.     

The Wacker Process: Inner‐ or Outer‐Sphere Nucleophilic Addition? New Insights from Ab Initio Molecular Dynamics

The Wacker process consists of the oxidation of ethylene catalyzed by a Pd^II complex. The reaction mechanism has been largely debated in the literature; two modes for the nucleophilic addition of water to a Pd‐coordinated alkene have been proposed: syn‐inner‐ and anti‐outer‐sphere mechanisms. These reaction steps have been theoretically evaluated by means of ab initio molecular dynamics combined with metadynamics by placing the [Pd(C₂H₄)Cl₂(H₂O)] complex in a box of water molecules, thereby resembling experimental conditions at low [Cl^?]. The nucleophilic addition has also been evaluated for the [Pd(C₂H₄)Cl₃]^? complex, thus revealing that the water by chloride ligand substitution trans to ethene is kinetically favored over the generally assumed cis species in water. Hence, the resulting trans species can only directly undertake the outer‐sphere nucleophilic addition, whereas the inner‐sphere mechanism is hindered since the attacking water is located trans to ethene. In addition, all the simulations from the [Pd(C₂H₄)Cl₂(H₂O)] species (either cis or trans) support an outer‐sphere mechanism with a free‐energy barrier compatible with that obtained experimentally, whereas that for the inner‐sphere mechanism is significantly higher. Moreover, additional processes for a global understanding of the Wacker process in solution have also been identified, such as ligand substitutions, proton transfers that involve the aquo ligand, and the importance of the trans effect of the ethylene in the nucleophilic addition attack.     

Mechanism of the Pd‐catalyzed Decarboxylative Allylation of α‐Imino Esters: Decarboxylation via Free Carboxylate Ion

The Pd‐catalyzed decarboxylative allylation of α‐(diphenylmethylene)imino esters ( 1 ) or allyl diphenylglycinate imines ( 2 ) is an efficient method to construct new C(sp³)? C(sp³) bonds. The detailed mechanism of this reaction was studied by theoretical calculations [ONIOM(B3LYP/LANL2DZ+p:PM6)] combined with experimental observations. The overall catalytic cycle was found to consist of three steps: oxidative addition, decarboxylation, and reductive allylation. The oxidative addition of 1 to [(dba)Pd(PPh₃)₂] (dba=dibenzylideneacetone) produces an allylpalladium cation and a carboxylate anion with a low activation barrier of +9.1 kcal mol^?1. The following rate‐determining decarboxylation proceeds via a solvent‐exposed α‐imino carboxylate anion rather than an O‐ligated allylpalladium carboxylate with an activation barrier of +22.7 kcal mol^?1. The 2‐azaallyl anion generated by this decarboxylation attacks the face of the allyl ligand opposite to the Pd center in an outer‐sphere process to produce major product 3 , with a lower activation barrier than that of the minor product 4 . A positive linear Hammett correlation [ρ=1.10 for the PPh₃ ligand] with the observed regioselectivity ( 3 versus 4 ) supports an outer‐sphere pathway for the allylation step. When Pd combined with the bis(diphenylphosphino)butane (dppb) ligand is employed as a catalyst, the decarboxylation still proceeds via the free carboxylate anion without direct assistance of the cationic Pd center. Consistent with experimental observations, electron‐withdrawing substituents on 2 were calculated to have lower activation barriers for decarboxylation and, thus, accelerate the overall reaction rates.     

Mechanistic aspects of ligand substitution on <Emphasis Type="Italic">cis</Emphasis>-diaqua(<Emphasis Type="Italic">cis</Emphasis>-1,2-diaminocyclohexane)platinum(II) by Glycine-<Emphasis Type="SmallCaps">l</Emphasis>-Leucine

The kinetics of the interaction of glycine-l-leucine (Glyleu) with cis-[Pt(cis-dach)(OH₂)₂]²⁺ (dach = 1,2-diaminocyclohexane) has been studied spectrophotometrically as a function of [cis-[Pt(cis-dach)(OH₂)₂]²⁺], [Glyleu] and temperature at pH 4.0, where the complex exists predominantly as the diaqua species and Glyleu as a zwitterion. The substitution reaction shows two consecutive steps: the first is the ligand-assisted anation and the second is the chelation step. The activation parameters for both the steps were evaluated using Eyring’s equation. The low ∆H₁^≠ (51.9 ± 2.8 kJmol⁻¹) and large negative value of ∆S₁^≠ (−152 ± 8 JK⁻¹mol⁻¹) as well as ∆H₂^≠ (54.4 ± 1.7 kJmol⁻¹) and ∆S₂^≠ (−162 ± 5 JK⁻¹mol⁻¹) indicate an associative mode of activation for both the aqua ligand substitution processes.     

Ruthenium(II) Complexes Containing Lutidine‐Derived Pincer CNC Ligands: Synthesis,Structure, and Catalytic Hydrogenation of CN bonds

A series of Ru complexes containing lutidine‐derived pincer CNC ligands have been prepared by transmetalation with the corresponding silver‐carbene derivatives. Characterization of these derivatives shows both mer and fac coordination of the CNC ligands depending on the wingtips of the N‐heterocyclic carbene fragments. In the presence of tBuOK, the Ru‐CNC complexes are active in the hydrogenation of a series of imines. In addition, these complexes catalyze the reversible hydrogenation of phenantridine. Detailed NMR spectroscopic studies have shown the capability of the CNC ligand to be deprotonated and get involved in ligand‐assisted activation of dihydrogen. More interestingly, upon deprotonation, the Ru‐CNC complex 5 e (BF₄) is able to add aldimines to the metal–ligand framework to yield an amido complex. Finally, investigation of the mechanism of the hydrogenation of imines has been carried out by means of DFT calculations. The calculated mechanism involves outer‐sphere stepwise hydrogen transfer to the C?N bond assisted either by the pincer ligand or a second coordinated H₂ molecule.     

Mechanistic study on the oxidation of l-phenylalanine by copper(III) in aqueous alkaline medium: a kinetic approach

Abstract  

Oxidation of the amino acid l-phenylalanine by diperiodatocuprate(III) in alkaline medium at constant ionic strength of 0.25 mol dm⁻³ was studied spectrophotometrically at different temperatures (298–313 K). The reaction between diperiodatocuprate(III) and l-phenylalanine in alkaline medium exhibits 1:2 stoichiometry. Intervention of free radicals was observed in the reaction. Based on the observed orders and experimental evidence, a mechanism involving monoperiodatocuprate(III) as the reactive oxidant species has been proposed, proceeding through the formation of a complex and reaction of the intermediate of l-phenylalanine with monoperiodatocuprate(III) to give the products. The products were identified by spot test, infrared (IR), and gas chromatography-mass spectrometry (GC-MS). The reaction constants involved in the different steps of the mechanism were calculated. The activation parameters with respect to the slow step of the mechanism were computed and are discussed. The thermodynamic quantities were determined for different equilibrium steps. The isokinetic temperature was also calculated and found to be 331 K.     

Electrochemical study of gallium(III) with <Emphasis Type="SmallCaps">l</Emphasis>-glutamine at the dropping mercury electrode

Abstract  

Gallium complexes of l-glutamine have been studied polarographically in aqueous media. The reduction was found to be irreversible and diffusion controlled in the presence of 0.1 M KNO₃ and 0.002% Triton-x-100. The values of kinetic parameters, transfer coefficient (α _n), and formal rate constant ( k_{\textf,\texth}⁰ k_{{{\text{f}},{\text{h}}}}^{0} ) of the electrode reactions were calculated by Koutecky's method. The stability constants and composition of the gallium(III)-l-glutamine complexes were evaluated with the help of the Deford-Hume method. The values of stability constants of 1:1, 1:2, and 1:3 gallium(III)-l-glutamine complexes are 1.35, 6.5, and 1,350 at 30 °C, respectively. The values of thermodynamic parameters, the free energy of activation, the enthalpy of activation, and the entropy of activation have been determined at 30 °C. The formation of the metal complexes has been found to be non-spontaneous, endothermic in nature, and entropically favorable at higher temperature.