Thermodynamic Functions Of Complex Formation Research Articles

A study of the inclusion complex of bioactive thiadiazole derivative with 2‑hydroxypropyl‑β‑cyclodextrin: Preparation, characterization and physicochemical properties

The main aim of this work has been to improve the solubility of bioactive 6-(acetylamino)-N-(5-ethyl-1,3,4-thiadiazol-2-yl)-hexanamide by forming an inclusion complex with 2-hydroxypropyl-β-cyclodextrin. UV–vis spectroscopy was applied to studying the host-guest interaction in the buffer solution pH 7.4. Phase solubility and Job's methods were used to confirm the formation of an inclusion complex with 1:1 stoichiometry and 103 kg·mol−1 stability constant. It has been established that in the presence of 0.069 mol·kg−1 of 2HP-β-CD, the compound solubility is equal to 11.60·10−3 mol·kg−1, which corresponds to a 7-time increase in this parameter compared to the solubility in pure buffer. The thermodynamic functions of complex formation have been determined and it has been found that the inclusion process is spontaneous and thermodynamically advantageous. Data from 1H NMR experiments also provided formation evidence of the inclusion complex between study compound and 2HP-β-CD. The inclusion complex in solid state has been obtained by grinding and characterized by differential scanning calorimetry, Fourier-transform infrared spectroscopy and X-ray diffractometry. The kinetic characteristics of dissolution process for the supramolecular complex have been obtained.

Effect of temperature and solvent properties on the process of complex formation between crown ether 15C5 and Na+ in the (propan-1-ol + water) mixture at temperatures from T = 293.15 K to T = 308.15 K

Thermodynamic functions of complex formation of 15-crown-5 ether (15C5) with sodium cation (Na+) in the mixtures of propan-1-ol (PrOH) with water (W) at different temperatures have been calculated. To obtain this function two experimental methods have been used. The equilibrium constants of complex formation (15C5/Na+) have been determined by conductivity measurements and the enthalpic effect of complex formation has been measured by the calorimetric method and has been also calculated using van’t Hoff’s equation. The complexes are enthalpy stabilized but entropy destabilized. Effect of solvent properties on the process of complex 15C5/Na+ formation in PrOH+W mixtures has been discussed. The obtained results were compared with analogous data in the mixtures of water with methanol or ethanol and discussed.

Effect of temperature on the process of complex formation crown ether 15C5 with Na+ in the (water + ethanol) mixture at temperatures from (293.15 to 308.15) K

• The system 15C5/Na + complex + water + ethanol has been investigated. • The thermodynamic functions of 15C5/Na + complex formation were calculated. • The enthalpy of complex formation has been calculated using calorimetric method. • The enthalpy of complex formation has been calculated from van’t Hoff's equation. • The obtained results have been compared. Thermodynamic functions of complex formation of 15-crown-5 ether (15C5) with sodium cation (Na + ) in the mixtures of water (W) with ethanol (EtOH) at different temperatures have been calculated. To obtain this function two experimental methods have been used. The equilibrium constants of complex formation have been determined by conductivity measurements and the enthalpic effect of complex formation has been measured by the calorimetric method and has been also calculated using van’t Hoff's equation. The obtained results were compared and discussed. The complexes are enthalpy stabilized but entropy destabilized.

Effect of temperature on the process of complex formation crown ether 15C5 with Na+ in the mixture of water with methanol

Thermodynamic functions of complex formation of 15-crown-5 ether (15C5) with sodium cation (Na+) in the mixtures of water (W) with methanol (MeOH) at different temperature have been calculated. To obtain this function two experimental methods have been used. The equilibrium constants of complex formation have been determined by conductivity measurements and the enthalpic effect of complex formation has been measured by the calorimetric method and has been also calculated using van’t Hoff’s equation. The obtained results were compared and discussed. The complexes are enthalpy stabilized but entropy destabilized.

Standard thermodynamic functions of complex formation between Cu2+ and glycine in aqueous solution

Heat effects of the interaction of copper(II) solutions with aminoacetic acid (glycine) are measured by the direct calorimetry at 298.15 K and ionic strengths of 0.5, 1.0, and 1.5 against a background of potassium nitrate. Standard enthalpy values for reactions of the formation of aminoacetic acid copper complexes in aqueous solutions are obtained using an equation with a single individual parameter by extrapolating it to zero ionic strength. The standard thermodynamic characteristics of complex formation in the Cu2+-glycine system are calculated. It is shown that glycine-like coordination is most likely in Cu(II) complexes with L-asparagine, L-glutamine, and L-valine.

Complex Formation of Crown Ethers and Cations in Water−Organic Solvent Mixtures: The Thermodynamic Functions of Complex Formation of Benzo-15-crown-5 with Na+ in Water + Ethanol at 298.15 K

The enthalpies of solution of benzo-15-crown-5 ether in ethanol + water and ethanol + water + sodium iodide systems have been measured at T = 298.15 K. The values of standard enthalpies of solution of benzo-15-crown-5 ether are positive in the mixtures of water and ethanol within the whole range of mixture composition. The equilibrium constants of complex formation of benzo-15-crown-5 ether with a sodium cation have been determined by conductivity measurements at T = 298.15 K. In the process of complex formation, ethanol molecules show their hydrophobic properties.

Erratum to: Complex Formation of Crown Ethers and Cations in Water–Organic Solvent Mixtures: Part XI. Effects of the Preferential Solvation of Benzo-15-Crown-5 and Acid-Base Properties of the Mixtures on the Thermodynamic Functions for Complex Formation of Benzo-15-Crown-5 with Na+ in Propan-1-ol–Water Mixtures at 298.15 K

The thermodynamic functions of complex formation of benzo-15-crown-5 ether (B15C5) and sodium cation (Na+) in the mixtures of propan-1-ol (PrOH) with water at 298.15 K have been calculated from experimental measurements. The equilibrium constants of B15C5/Na+ complex formation have been determined by conductivity measurements. The enthalpic effect of complex formation has been measured by a calorimetric method. The complexes are enthalpy stabilized but entropy destabilized in the PrOH–H2O mixtures. The effects of preferential solvation of B15C5 by molecules of the organic solvent, solvation of the sodium cation, as well as the acid-base properties of propan-1-ol–water mixtures on the complex formation processes are discussed.

Complex Formation of Crown Ethers and Cations in Water–Organic Solvent Mixtures: Part XII. Effect of the Acid–Base Properties of the Mixture on the Thermodynamic Functions of Complex Formation of Benzo-15-Crown-5 with Na+ in Water–Methanol Mixtures at 298.15 K

The enthalpies of solution of benzo-15-crown-5 ether in methanol–water mixtures and methanol–water–sodium iodide systems have been measured at 298.15 K. The values of standard enthalpies of solution of benzo-15-crown-5 ether are positive in the mixtures of water and methanol within the whole range of mixture composition. The equilibrium constants of complex formation of benzo-15-crown-5 ether with the sodium cation have been determined by conductivity measurements at 298.15 K. The thermodynamic functions of the formation of these complexes have been calculated. The Gibbs energy of complex formation depends on the base–acid properties of methanol–water mixture.

Thermodynamic characteristic of complex formation of some metals with 3-(4-chlorophenylazo)pentane-2,4-dione in aqueous ethanol

Effective charges of atoms in tautomeric forms (enol-azo, keto-azo, hydrazo) of 3-(4-chlorophenylazo) pentane-2,4-dione (L) have been determined by MO LCAO in the Huckel approximation. The complex formation of a series of metals with L in aqueous ethanol has been investigated by potentiometric and conductometric titration. Based on the results of potentiometric titration, the standard thermodynamic functions of complex formation have been established. They vary in the following order: $$ \begin{gathered} \left| {\Delta G^0 } \right|:Fe > Cu > Co > Ni > UO_2 > Cd > Zn > Mn > Mg > Ca, \hfill \\ \left| {\Delta H^0 } \right|:Fe > Cu > UO_2 > Ni > Co > Zn > Cd > Mn > Mg > Ca, \hfill \\ \Delta S^0 :Ca > Mg > Mn > Cd > Co > Zn > Ni > Cu > Fe > UO_2 . \hfill \\ \end{gathered} $$ The complex of copper(II) with L has been identified by X-ray diffraction, and its thermal properties have been studied.

The effect of carbonyl carbon atom replacement in acetone molecule (ACN) by sulfur atom (DMSO): Part II. Thermodynamic functions of complex formation of crown ethers with Na+ in mixed solvents

The thermodynamic functions of complex formation of benzo-15-crown-5 ether (B15C5) and sodium cation (Na+) in acetone–water mixtures at 298.15 K have been calculated. The equilibrium constants of B15C5/Na+ complex formation have been determined by conductivity measurements. The enthalpic effect of complex formation has been measured by the calorimetric method. The complexes are enthalpy-stabilized but entropy-destabilized in acetone–water mixtures. The effects of hydrophobic hydration, preferential solvation of B15C5 by a molecule of water and acetone, respectively and the solvation of Na+ on the complex formation processes have been discussed. The calculated thermodynamic functions of B15C5/Na+ complex formation and the effect of benzene ring on the complex formation have been compared with analogous data obtained in dimethylsulfoxide–water mixtures. The effect of carbonyl atom replacement in acetone molecule by sulphur atom (DMSO molecule) on the thermodynamic functions of complex formation has been analysed.

Complex formation of crown ethers with cations in water–organic solvent mixtures: Part X. Thermodynamics of interactions between Na + ion and 15-crown-5 ether in acetone–water mixtures at 298.15 K

The thermodynamic functions of complex formation of 15-crown-5 ether (15C5) with sodium cation (Na +) in the mixtures of water with acetone at 298.15 K have been calculated. The equilibrium constants of complex formation of 15C5 with Na + have been determined by conductivity measurements. The enthalpic effect of complex formation has been measured by the calorimetric method. The complexes are enthalpy-stabilized but entropy-destabilized in acetone–water mixtures. The effects of hydrophobic hydration, preferential solvation of 15C5 by a molecule of organic solvent and solvation of Na + on the complex formation processes have been discussed.

Thermodynamics of the effects of substituent, degree of substitution, and pH on complex formation of hydroxypropyl-α- and hydroxypropyl-β-cyclodextrins with ascorbic acid

The interaction of ascorbic acid with hydroxypropyl-α- and hydroxypropyl-β-cyclodextrins of different degree of substitution was studied at 298.15 K and different pH using solution calorimetry. In an aqueous solution, only hydroxypropyl-β-cyclodextrins form weak molecular complexes with the nonionized form of ascorbic acid. The thermodynamic functions of complex formation and stability constants of the complexes were calculated. The systems with weak intermolecular interaction without complex formation were characterized by enthalpic virial coefficients. On the basis of the obtained thermodynamic characteristics it was shown that the selectivity of complex formation of hydroxypropyl-α- and hydroxypropyl-β-cyclodextrins with ascorbic acid is determined by the size of the macrocyclic cavity, the presence of the hydroxypropyl substituent, and the medium acidity. The degree of substitution of hydroxypropyl-β-cyclodextrins exerts no substantial effect on the thermodynamic parameters of interaction with ascorbic acid.

Complex formation of crown ethers with cations in the (water + organic solvent) mixtures: Part IX. Thermodynamics of interactions of Na + ion with benzo-15-crown-5 ether in {(1 − x)DMA + xH 2O} at T = 298.15 K

The thermodynamic functions of complex formation of benzo-15-crown-5 ether with sodium cation in {(1 − x)DMA + xH 2O} at T = 298.15 K have been calculated. The equilibrium constants of complex formation of benzo-15-crown-5 ether with sodium cation have been determined by conductivity measurements. The enthalpic effect of complex formation has been measured by calorimetric method at T = 298.15 K. The complexes are enthalpy stabilized and entropy destabilized. A simple model has been proposed to describe the relationship between the thermodynamic functions of complex formation of crown ethers with sodium cation and the structural and energetic properties of the mixed water–organic solvent. The linear enthalpy–entropy relationship for complex formation is also presented. The solvation enthalpy of the complex in {(1 − x)DMA + xH 2O} is discussed.

Complex Formation of Crown Ethers with Cations in the Water–Organic Solvent Mixtures. Part VIII. Thermodynamic of Interactions of Na+Ion with 15-Crown-5 and Benzo-15-Crown-5 Ethers in the Mixtures of Water with Hexamethylphosphortriamide at 298.15 K

The equilibrium constants of complex formation of 15-crown-5 and benzo-15-crown-5 ethers with the sodium cation have been determined by conductivity measurements. The enthalpic effect of complex formation has been measured by a calorimetric method at 298.15 K. The thermodynamic functions of complex formation of 15-crown-5 and benzo-15-crown-5 ethers with the sodium cation in the mixtures of water with hexamethylphosportriamide at 298.15 K have been calculated. The extent of complex formation in this mixed solvent depends on the enthalpic effect. In water–hexamethylp- hosportriamide mixtures with medium and low water content, the complex of crown ethers with the sodium cation is not formed because of the strong solvation of sodium cation and crown ethers molecules; this implies that the entropy of complex formation is more negative than the enthalpy of complex formation.

Complex formation of crown ethers with cations in the (water + organic solvent) mixtures. Part VI. Thermodynamic of interactions of Na + ion with benzo-15-crown-5 ether in {(1− x)DMF + xH 2O} at 298.15 K

The equilibrium constants of complex formation of benzo-15-crown-5 ether with sodium cation in {(1− x)DMF + xH 2O} were calculated using conductometric measurements. The thermodynamic functions of complex formation, the transfer enthalpy of complex from DMF to mixed solvent and the influence of benzene ring on the process of complex formation were calculated and discussed together with the same function in {(1− x)DMSO + xH 2O}. A good relationship between the enthalpy and entropy of complex formation was observed.

Complex formation of crown ethers with cations in the water-organic solvent mixtures. Part V. Thermodynamic of interactions of Na + ion with 15-crown-5-ether in the mixtures of water with N,N-dimethylformamide at 298.15 K

The equilibrium constants of complex formation of 15-crown-5-ether with sodium iodide have been determined by conductivity measurements in the mixtures of water with N,N-dimethylformamide-water-sodium iodide system have been measured at 298.15 K. The N,N-dimethylformamide at 298.15 K. Standard enthalpies of solution of crown ether in the thermodynamic functions of complex formation of 15-crown-5-ether with sodium iodide are discussed. The complex formation in this mixed solvent depends on the enthalpic effect. The linear enthalpy-entropy relationship for complex formation is presented. The transfer enthalpy of the complex from pure N,N-dimethylformamide to the examined mixtures were calculated and discussed.

Complex formation of crown ethers with cations in water-organic solvent mixtures.: Part II. Thermodynamics of interactions of Na + ion with benzo-15-crown-5 ether in the mixtures of water with dimethylsulfoxide at 298.15 K

The equilibrium constants of complex formation of crown ether (benzo-15-crown-5 ether) with sodium cation have been determined by molar conductance at various molar ratios of benzo-15-crown-5 ether and sodium iodide in the mixtures of water with dimethylsulfoxide at 298.15 K. The solution enthalpy of benzo-15-crown-5 ether in the dimethylsulfoxide-water-sodium iodide system has been measured at 298.15 K. The thermodynamic functions of complex formation of benzo-15-crown-5 ether with sodium iodide were calculated. The linear enthalpy-entropy relationship for complex formation was discussed. The transfer enthalpy of the benzo-15-crown-5 ether/Na + complex from pure dimethylsulfoxide to the examined mixtures was calculated and discussed. The contribution of the benzene ring in the thermodynamic functions of complex formation and in the standard enthalpy of complex solvation was analysed.

Complex Formation of Crown Ethers with Cations in Water–Organic Solvent Mixtures. Part IV. Thermodynamics of Interaction of Na+Ion with Benzo-15-crown-5 Ether in the Mixtures of Water with Acetonitrile at 298.15 K

Abstract The equilibrium constants of complex formation of crown ether (benzo-15-crown-5 ether) with sodium cation have been determined by molar conductance at various molar ratios of benzo-15-crown-5 ether and sodium iodide in the mixtures of water with dimethylsulfoxide at 298.15 K. The solution enthalpy of benzo-15-crown-5 ether in the dimethylsulfoxide-water-sodium iodide system has been measured at 298.15 K. The thermodynamic functions of complex formation of benzo-15-crown-5 ether with sodium iodide were calculated. The linear enthalpy-entropy relationship for complex formation was discussed. The transfer enthalpy of the benzo-15-crown-5 ether/Na + complex from pure dimethylsulfoxide to the examined mixtures was calculated and discussed. The contribution of the benzene ring in the thermodynamic functions of complex formation and in the standard enthalpy of complex solvation was analysed.

Comparison of yttrium, lanthanides and actinides in respect to unit cell volumes of isostructural compounds and thermodynamic functions of complex formation

The investigations carried out till now and presented in this paper show that apart from the well known itinerant properties of yttrium in respect to free energy of complex formation, also actinides(III) change their position in the lanthanide series in respect to ΔG. It has also been shown that yttrium and actinides exhibit itinerant behaviour in respect to unit cell volumes. Evidence has been presented that delocalization of 4f and 5f orbitals is the reason for the two types of migratory properties. Since the itinerant behaviour of yttrium and actinides(III) in respect to stability constants (free energies of complex formation) is the basis for yttrium-lanthanides and lanthanides-actinides group separations, a better qualitative understanding of the mechanism involved may contribute to the development of more efficient separation procedures.

The position of plutonium/III/ in the lanthanide series in respect to thermodynamic functions of complex formation with nitrates and thiocyanates

The position of Pu/III/ within lanthanides in respect to ΔG0, ΔH0 and ΔS0 of complex formation with nitrate and thiocyanate ligands was determined by the extraction method. It was found that in respect to ΔG0, Pu/III/ is a light pseudolanthanide for nitrate ligands and a heavy pseudolanthanide for thiocyanate ligands. A comparison of the positions of Pu/III/ and Am/III/ in respect to ΔG0, ΔH0 and ΔS0 shows that the radius of plutonium is greater than that of americium in the An/NO3/ 5 2− complex and smaller in the An/NCS/3/TBP/n complex. The increase in the radii between plutonium and americium in the thiocyanate complex points out to a contribution from 5f orbitals to bonding.