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![Figure 2. Molar conductance vs. [crown]/[Tl + ] for various crown-Tl +...](profile/Sattar-Shariati/publication/251262148/figure/fig2/AS:1116376769015808@1643176371356/Molar-conductance-vs-crown-Tl-for-various-crown-Tl-systems-in-60-DMF-1_Q320.jpg)
![Figure 3. Molar conductance vs. [A18C6]/[Tl + ] plots in 80% DMF at...](profile/Sattar-Shariati/publication/251262148/figure/fig3/AS:1116376769015809@1643176371370/Molar-conductance-vs-A18C6-Tl-plots-in-80-DMF-at-different-temperatures-1-15_Q320.jpg)
The complexation reactions between Tl+ ion and dibenzo-30-crown-10 (DB30C10), dibenzo-24-crown-8 (DB24C8), dibenzo-21-crown-7 (DB21C7), and aza-18-crown-6 (A18C6) were studied in different dimethylformamide-acetonitrile mixtures at various temperatures. The formation constants of the resulting 1 : 1 complexes were determined from the molar conducta...
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This chapter deals with how one can obtain values of thermodynamic properties - specifically the apparent equilibrium constant K', the stan- dard molar transformed Gibbs energy change DrG', and the standard molar transformed enthalpy change DrH' for biochemical reactions - and, in particular, for enzyme-catalyzed reactions. In addition to direct me...
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... Some techniques such as, potentiometry [17,18], conductometry [19][20][21][22][23], spectrophotometry [24], polarography [25][26], calorimetry [27] and NMR spectrometry [28][29] have been used to study the complex formation between macrocyclic compounds with different metal ions in solutions. Among these various methods, the conductometric technique is a sensitive and inexpensive method with a simple experimental arrangement for such investigations. ...
... Conductance: Program based mathematical calculation of non-linear changes in the conductivity data and association constants K ( ) a C . Non-linear changes in the conductivity data at the temperature ranging from 298.15 K to 308.15 K were utilized in the mathematical program and the association constants K ( ) a c for1:1 DGs-CDs ICs, listed in the Table 3 are frequently obtained [49][50][51] . The complexation reaction between DGs and CDs to produce ICs is supposed to proceed via the following chemical equilibrium ...
Host-guest interaction of two significant drugs, phenylephrine hydrochloride and synephrine with α and β-cyclodextrins were studied systematically. Initially two simple but reliable physicochemical techniques namely conductance and surface tension were employed to find out saturation concentration for the inclusion and its stoichiometry. The obtained 1:1 stoichiometry was further confirmed by two spectrometric methods, UV-Vis study and spectrofluorimetry. Significant shifts in IR stretching frequency also support the inclusion process. Relative stabilities of the inclusion complexes were established by the association constants obtained from UV-Vis spectroscopic measurements, program based mathematical calculation of conductivity data. Calculations of the thermodynamic parameters dictates thermodynamic feasibility of the inclusion process. Spectrofluorometric measurement scaffolds the UV-Vis spectroscopic measurement validating stability of the ICs once again. Mass spectroscopic measurement gives the molecular ion peaks corresponding to the inclusion complex of 1:1 molar ratio of host and guest molecules. The mechanism of inclusion was drawn by 1H-NMR and 2D ROESY spectroscopic analysis. Surface texture of the inclusion complexes was studied by SEM. Finally, the cytotoxic activities of the inclusion complexes were analyzed and found, Cell viability also balances for non-toxic behavior of the ICs. Moreover, all the studies reveal the formation of inclusion complexes of two ephedra free, alternatively emerging drugs (after their banned product having ephedra) SNP, PEH with α and β-CD which enriches the drug delivery system with their regulatory release without any chemical modification.
... So from the value of intercept and slope we can easily calculate ΔS0 and ΔH0 and also ΔG of the formation of the inclusion complexes (reported in the Table 1). The negativeΔGvalues signify the spontaneityof the process [27,28]. ...
In this present work we studied the supramolecular interaction of 1-hexyl-3-methylimidazolium hexaflurophosphate(HMIm)PF6with α-cyclodextrin (α-CD) and β-cyclodextrin (β-CD) using various physicochemical method and spectroscopic technique. The formation of inclusion complex of any ionic liquid inside the cyclodextrin affects the physicalchemical properties like solubility, conductivity, surface tension, etc. So from the discrepancy of physicochemical andspectral properties we can confirm the formation inclusion complex. The stoichiometry of host-guest of the inclusion complexes was evaluated from conductivity, surface tensionstudy and Job's plot from UV-visible spectroscopy. We also calculated the association/binding constant from conductivity, surface tension measurements and Benesi-Hildebrand equation. The infra-red (IR) and 1 H NMR spectroscopy also affirm the formation of inclusion complexes however the plausible mode of inclusion was described from 1 H NMR and 2D ROESY NMR spectroscopies.
... A gradual decrease in conductance is observed with increasing CE/IL mole ratio for each plot, which signifies capture of the cetylpyridinium ions by the CEs respectively in CH 3 CN solution, because CPCl being strong electrolyte can't form ion pair in the studied solution system [37]. So the complexation processes of cetylpyridinium ion with the three CEs which have been illustrated by decrease in conductance in Fig. 1e3, become approximately plateau as the CE/IL mole ratio exceed 1.0, evidently suggesting development of adequately stable 1:1 CPCl-CE complex in CH 3 CN solution system [38]. Each of the figures (Figs. 1e3) shows five various curve at different temperatures, all exhibiting analogous variation in conductance. ...
Supramolecular complexations of cetylpyridinium chloride with three comparable cavity dimension based crown ethers, namely, dibenzo-18-crown-6, 18-crown-6 and dicyclohexano-18-crown-6 have been explored and adequately compared in acetonitrile with the help of conductivity in a series of temperatures to reveal the stoichiometry of the three host-guest complexes. Programme based mathematical treatment of the conductivity data affords association constants for complexations from which the thermodynamic parameters were derived for better comprehension about the process. The interactions at molecular level have been explained and decisively discussed by means of FT-IR and ¹H NMR spectroscopic studies that demonstrate H-bond type interactions as the primarily force of attraction for the investigated supramolecular complexations.
... Quantitative data about the formation of the complexes may be obtained by non-linear programmed mathematical treatment based on the change in conductance according to 1:1 CE-IL complexation at different temperatures [26,27]. ...
... The association constant (K a ) for the formation of complex (CX) may be expressed as According to the programmed non-linear isotherm, in dilute solution the association constant (K a ) for the formation of CX may be expressed as [25,27] ...
... Under the dilute conditions used, the activity coefficient of the uncharged macrocycle, f(C), can be reasonably assumed as unity. 28 The use of the Debye-Hückel limiting law 29 leads to the conclusion that f(M + ) $ f(MC + ); therefore, the activity coefficients in eqn (2) cancel. The complex formation constant in terms of the molar conductances, L, can be expressed as: 25,28 ...
Inclusion complex formation between hollow circular compounds, e.g. crown ethers, and an ionic liquid, 1-methyl-3-octylimidazolium tetrafluoroborate, in acetonitrile solvent is studied by means of conductivity measurements, IR spectra and NMR spectra. The results reveal the formation of 1 : 1 complexes between the crown ethers and ionic liquid molecules in acetonitrile. Crown ether complexes with electron-deficient imidazolium cations are formed by H-bond formation between the acidic protons of the imidazolium ring of the ionic liquid and the lone pair of electrons of the crown oxygen atom. In the case of dibenzo-18-crown-6, complexation is caused by H-bonding; however, π-stacking or charge-transfer interactions also appear to have minor contributions to the complex formation. Thus, hydrogen bonding is mainly responsible for the complexation, and ion-dipole interactions also may be responsible for complex formation between ionic liquid molecules and the crown ethers. The interactions in the complexation are analyzed and discussed.
... The results of calculated standard enthalpy, ðDH C Þ and standard entropy, ðDS C Þ are listed in Table 3. As shown in Table 3, the complexes in all cases are entropy stabilized (DS C > 0) where entropy acts as the principal driving force for the formation of these complexes in all solvent systems [42]. ...
... DG C ± SD (kJ mol À1 ) DH C ± SD (kJ mol À1 ) DS C ± SD J/mol K values of enthalpy changes, DH C are obtained from the Van't Hoff plots, while the entropy changes, DS C , are calculated from the following equation [42]: ...
Thermodynamic aspects of complexation process between 14-membered tetra-aza macrocycle ligand and four metal cations were studied in ethanol–water (EtOH–H2O) binary mixtures at different temperatures by applying conductometric method. In all the cases, the stability constants (logKf) of 1:1 formed complexes between ligand and cations were obtained by fitting the molar conductivity curves using the Genplot computer program
and the formation constant values (logKf) were generally in the range of 1.41–2.70. The values of thermodynamic parameters, standard enthalpy and standard entropy were obtained from the temperature dependence of the stability constants using the Van’t Hoff plots. Complexes in every cases were found to be entropy stabilized, and the selectivity order of all the complexes changes as well as the changes in composition of the solvent mixtures. The experimental data was tested by using artificial neural network
(ANN) technique and was in a good agreement with estimated data.
... The deviations from ideal behavior are indicative of the extent of preferential solvation and the existence of specific solvent-solute and solvent-solvent interactions [8,9]. Although the complexation reaction of macrocyclic polyethers with metal cations has been extensively studied during the past three decades, little attention has been paid to the study of non-metal cations complexations in mixed solvents [2,3,[10][11][12][13][14][15][16][17][18][19][20]. ...
The complexation reaction between hydroxyl ammonium (HONH3+) cation with 18-crown-6 (18C6) ligand was studied in dimethylsulfoxide - water (DMSO-H2O), methanol water (MeOH-H2O) and dimethylformamid - methanol (DMF-MeOH), binary solutions at different temperatures using conductometric method. The obtained results show that the stoichiometry of the complex formed between HONH3+ cation with (18C6) in all of the binary mixed solvents is 1:1[ML], as well as, these results show that the nature and the composition of the solvent systems are important factors that are effective on the stability of the complex formed between the macrocyclic ligand and metal cation in solutions. A non-linear behavior was observed for changes of stability constants of the complex versus the composition of the binary mixed solvents. The values of thermodynamic parameters show that the thermodynamics of complexation reaction is affected by the nature and composition of the mixed solvents and the complex is entropy stabilized, but enthalpy destabilized in most compositions of binary solutions.
... The use of Debye-Huckel limiting law leads to the conclusion that, f M nþ *f ML nþ , therefore, the activity coefficients in Eq. 2 could be canceled. The complex formation constant in terms of the molar conductance can be expressed as [16,17]: ...
... Therefore, we should not expect a monotonic relationship between these thermodynamic quantities and the solvent composition. Similar behaviors have already been reported for various metal cation-crown ether complexes in different binary mixed solvents [12][13][14][15][16][17][18]23]. ...
The complexation reaction of dibenzo-18-crown-6 (DB18C6) with ZrO2+ cation was studied in some binary solvent solutions of acetonitrile (AN), 1,2 dichloroethane (DCE), nitromethane (NM) and
ethylacetate (EtOAc) with methanol (MeOH), at different temperatures by conductometry method. The stability constant of the
resulting 1:1 complex at each temperature was determined using a computer fitting conductance-mole ratio data. The results
revealed that, the (DB18C6·ZrO)2+ complex is more stable in the EtOAc–MeOH binary mixed solvents compared with the other binary mixed solvent solutions. A
non-linear relationship was observed for changes of log Kf of (DB18C6·ZrO)2+ complex versus the composition of the binary mixed solvents. The corresponding standard thermodynamic parameters (ΔHc°, ΔSc°) were obtained from temperature dependence of the stability constant. The results show that the (DB18C6·ZrO)2+ complex is enthalpy destabilized but entropy stabilized and the values along with the sign of these parameters are influenced
by the nature and composition of the mixed solvents.
... The enthalpy and entropy values of complexation reactions are influenced by the amount of cation-solvent, macrocyclic compounds-solvent, complex-solvent and even solvent-solvent interactions [13,14]. Owing to the extensive use of non-aqueous solvents in a wide range of pure and applied chemistry experiments, which have led to rapid progression in chemical science technologies, it was of interest to extend our study to the mixed binary non-aqueous solvents. ...
... This is due to variations in the extent of the contribution of such important parameters as solvation-desolvation of the species involved in the complexation reaction (i.e., Cs + cation, ionophore and the resulting complex). It is known that, the enthalpy and entropy of the formed complexes between macrocyclic compound and cations change with different factors such as variation in the flexibility of macrocyclic ionophore during the complexation process and the amount of cation-solvent, ionophore-solvent, complex-solvent and even solvent-solvent interactions [13,14]. ...
The complexation reactions between the macrocyclic ionophore, p-isopropylcalix[6]arene and Cs+ cation were studied in dimethylsulfoxide-acetonitrile (DMSO-AN) binary non-aqueous solvents at different temperatures using a conductometry method. The conductance data show that the stoichiometry of the (p-isopropylcalix[6]-arene·Cs)+ complex in all binary mixed solvents is 1:1. The stability of the complexes is affected by the composition of the binary solvent media and a non-linear behavior was observed for changes of log K(f) of the complex versus the composition of the binary mixed solvents. The thermodynamic parameters (DH°(c) and DS°(c)) for formation of (p-isopropyl-calix[6]arene·Cs)+ complex were obtained from temperature dependence of the stability constant and the obtained results show that the (p-isopropylcalix[6]arene·Cs)+ complex is enthalpy destabilized, but entropy stabilized, and the values of the mentioned parameters are affected strongly by the nature and composition of the binary mixed solvents.
