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Gholam Hossein Rounaghi - One of the best experts on this subject based on the ideXlab platform.

  • Study of Complex Formation between Kryptofix 21 with La3+, Y3+ and Ce3+ Cations in Some Binary Mixed Non-Aqueous Solvents Using the Conductometric Method
    Russian Journal of Inorganic Chemistry, 2016
    Co-Authors: S. Mahdizadeh, Gholam Hossein Rounaghi, M Mohajeri, F. Karimian
    Abstract:

    The complexation reactions between La3+, Y3+ and Ce3+ cations with the macrocyclic ligand, kryptofix 21, were studied in methanol-acetonitrile (MeOH-AN) and methanol-methylacetate (MeOHMeOAc) binary mixed solvent solutions at different temperatures using the Conductometric Method. The conductance data show that in most solvent systems, the kryptofix 21 forms a 1: 1 [M: L] complex with La3+, Y3+ and Ce3+ metal cations, but in the case of Y3+ cation in pure methylacetate, in addition of formation of a 1: 1 [ML] complex, 1: 2 [ML2] and 1: 3 [ML3] complexes are formed in solution. In the case of Ce3+cation, a 1: 1 [ML] and also a 1: 2 [ML2] complexes are formed in this solvent system at all studied temperatures. The electrical conductance data in acetonitrile, show that a 1: 1 [ML] and also a 1: 2 [ML2] complexes are formed between the ligand and La3+ and Ce3+ metal cations at different temperatures. The stability constants of the 1: 1 [ML] complexes were determined using the Conductometric data and a computer program, GENPLOT. A non-monotonic relationship was observed between logKf of the 1: 1 complexes with the composition of the binary solvent solutions which was discussed in term of solvent-solvent interactions and also preferential solvation of the metal cations and the ligand in solutions. The selectivity order of the ligand for the metal cations in MeOH–AN and MeOH–MeOAc binary solvent solutions, at 25°C was found to be: Y3+ > La3+ > Ce3+ and La3+ > Y3+ > Ce3+, respectively. The values of the standard thermodynamic quantities (ΔHc° and ΔSc°) for formation of the 1: 1 complexes were obtained from temperature dependence of the stability constans of the complexes and the results show that the thermodynamics of the complexation reactions between kryptofix 21 and La3+, Y3+ and Ce3+ cations, is affected by the nature and composition of the mixed solvents systems.

  • Study of complex formation between dicyclohexyl-18-crown-6 and UO22+ cation in some binary mixed non-aqueous solvents using Conductometric Method
    Journal of Inclusion Phenomena and Macrocyclic Chemistry, 2011
    Co-Authors: Fahimeh Razghandi, Gholam Hossein Rounaghi, Z. Eshaghi
    Abstract:

    In the present work, the complexation process between UO2 2+ cation and the macrocyclic ligand, dicyclohexyl-18-crown-6 (DCH18C6) was studied in ethyl acetate/1,2-dichloroethane (EtOAc/DCE), acetonitrile/1,2-dichloroethane (AN/DCE), methanol/1,2-dichloroethane (MeOH/DCE) and ethanol/1,2-dichloroethane (EtOH/DCE) binary solutions at different temperatures using the Conductometric Method. The conductance data show that in most cases, the stoichiometry of the complex formed between DCH18C6 and UO2 2+ cation is 1:1 [M:L], but in some solvent systems also a 1:2 [M:L2] complex is formed in solutions. The values of stability constant of (DCH18C6·UO2)2+ complex which were obtained from Conductometric data, show that the stability of the complex is affected by the nature and also the composition of the solvent system and in all cases, a non-linear behavior is observed for the variation of (log K f) of the (DCH18C6·UO2)2+ complex versus the composition of the binary mixed solvents. The values of thermodynamic quantities \( \Updelta H_{c}^{\circ} \) and \( \Updelta S_{c}^{\circ} \) for formation of (DCH18C6·UO2)2+ complex were obtained from temperature dependence of the stability constant using the van’t Hoff plots. The experimental results show that depending on the nature and composition of the solvent systems, the complex is enthalpy stabilized or destabilized, but in most cases, it is stabilized from entropy view point and both thermodynamic parameters are affected by the nature and composition of the binary mixed solutions.

  • solvent influence upon complex formation between benzo 15 crown 5 and mg2 ca2 and sr2 cations in some pure and binary mixed solvents using Conductometric Method
    Journal of Inclusion Phenomena and Macrocyclic Chemistry, 2010
    Co-Authors: Gholam Hossein Rounaghi, M Mohajeri, M Doaei, A Ghaemi
    Abstract:

    The complexation reactions between Mg2+, Ca2+ and Sr2+ cations with the macrocyclic ligand, benzo-15-crown-5 (B15C5), in pure acetonitrile, water, methanol and tetrahydrofuran and also in acetonitrile–water (AN–H2O) and in methanol–tetrahydrofuran (MeOH–THF) binary mixtures have been studied at different temperatures using Conductometric Method. The conductance data show that the stoichiometry of the complexes in most cases is 1:1 [ML]. But in the case of Ca2+ cation a 1:2 [ML2] complex is formed in pure THF, which shows that the stoichiometry of the complexes may be changed by the nature of the medium. The values of stability constants of complexes, which were obtained from Conductometric data, show that the stability of complexes is affected by the nature and composition of the binary mixed solvents and a non-linear behavior was observed for variation of logKf of the complexes versus the composition of the solvent systems. The results show that the selectivity order of B15C5 for the metal cations in two AN–H2O binary solutions (mol% AN = 25.71 and 50.94) at 25 °C is: Mg2+ > Sr2+ > Ca2+. The values of thermodynamic parameters (ΔHc0, ΔSc0) for formation of complexes were obtained from temperature dependence of stability constants of complexes using the van’t Hoff plots. The results show that the values and also the sign of these parameters are influenced by the nature and also the composition of the binary mixed solvents.

  • a thermodynamic study of complex formation between dicyclohexyl 18 crown 6 dch18c6 and la3 uo22 ag and nh4 cations in acetonitrile tetrahydrofuran binary media using Conductometric Method
    Russian Journal of Coordination Chemistry, 2008
    Co-Authors: Gholam Hossein Rounaghi, Somayeh Heydari
    Abstract:

    The complex formation between La3+, UO22+ Ag+, and NH4+ cations and macrocyclic ligand, dicyclohexyl-18-crown-6 (DCH18C6), was studied in acetonitrile-tetrahydrofuran (AN-THF) binary mixtures at different temperatures using the Conductometric Method. The results show that with the exception of complexation of the NH4+ cation with DCH18C6 in pure acetonitrile, the stoichiometry of all the complexes is being 1: 1 (M: L). The stability constants of the complexes were determined using a GENPLOT computer program. The nonlinear behavior which was observed for changes of log Kf of the complexes versus the composition of the mixed solvent was discussed in terms of solvent-solvent interaction in their binary solution, which results in changing the chemical and physical properties of the constituent solvents when they mix with one another and, therefore, changing the solvation capacities of the metal cations, crown ether molecules, and even the resulting complexes with changing the mixed solvent composition. The results show that the selectivity of DCH18C6 for the studied cations changes with the composition of the AN-THF binary system. The sequence of stabilities of complexes in an AN-THF binary solution (mol. % AN = 75.0) at 25°C is [(DCH18C6)La)]3+ > [(DCH18C6)UO2]2+ > [(DCH18C6)Ag]+ ∼ [(DCH18C6)NH4]+, but in the case of other binary systems of AN/THF (mol. % AN = 25.0 and 50.0) is [(DCH18C6)La]+ > [(DCH18C6)NH4]+ ∼ [DCH18C6)UO2]2+ > [(DCH18C6)Ag]+.

  • A thermodynamic study of complex formation between dicyclohexyl-18-crown-6 (DCH18C6) and La3+, UO22+, Ag+, and NH4+ cations in acetonitrile-tetrahydrofuran binary media using Conductometric Method
    Russian Journal of Coordination Chemistry, 2008
    Co-Authors: Gholam Hossein Rounaghi, Somayeh Heydari
    Abstract:

    The complex formation between La3+, UO22+ Ag+, and NH4+ cations and macrocyclic ligand, dicyclohexyl-18-crown-6 (DCH18C6), was studied in acetonitrile-tetrahydrofuran (AN-THF) binary mixtures at different temperatures using the Conductometric Method. The results show that with the exception of complexation of the NH4+ cation with DCH18C6 in pure acetonitrile, the stoichiometry of all the complexes is being 1: 1 (M: L). The stability constants of the complexes were determined using a GENPLOT computer program. The nonlinear behavior which was observed for changes of log Kf of the complexes versus the composition of the mixed solvent was discussed in terms of solvent-solvent interaction in their binary solution, which results in changing the chemical and physical properties of the constituent solvents when they mix with one another and, therefore, changing the solvation capacities of the metal cations, crown ether molecules, and even the resulting complexes with changing the mixed solvent composition. The results show that the selectivity of DCH18C6 for the studied cations changes with the composition of the AN-THF binary system. The sequence of stabilities of complexes in an AN-THF binary solution (mol. % AN = 75.0) at 25°C is [(DCH18C6)La)]3+ > [(DCH18C6)UO2]2+ > [(DCH18C6)Ag]+ ∼ [(DCH18C6)NH4]+, but in the case of other binary systems of AN/THF (mol. % AN = 25.0 and 50.0) is [(DCH18C6)La]+ > [(DCH18C6)NH4]+ ∼ [DCH18C6)UO2]2+ > [(DCH18C6)Ag]+.

Somayeh Heydari - One of the best experts on this subject based on the ideXlab platform.

  • Thermodynamic study of complex formation of β-cyclodextrin with ibuprofen by Conductometric Method and determination of ibuprofen in pharmaceutical drugs
    Arabian Journal of Chemistry, 2017
    Co-Authors: Somayeh Heydari, Roya Mohammadzade Kakhki
    Abstract:

    Abstract The equilibrium constants and the thermodynamic parameters for complex formation of β-cyclodextrin (β-CD) with ibuprofen have been determined by conductivity measurements in water. The inclusion complexation of ibuprofen in β-cyclodextrin (β-CD) has been examined by means of the Conductometric Method. The results suggest that stable1:1 complex is formed between ibuprofen and β-cyclodextrin. The thermodynamic parameters ( Δ H c ° , Δ S c ° ) for this complexation reaction have been determined from temperature dependence of the stability constant using the van’t Hoff plots. Based on the obtained results, a Conductometric Method for the determination of ibuprofen in the presence of β-CD at 25 °C was developed in the range of 10−3–10−5 mol dm−1. The Method was satisfactorily applied to the quantification of ibuprofen in pharmaceutical preparations.

  • A simple Conductometric Method for trace level determination of brilliant green in water based on β-cyclodextrin and silver nitrate and determination of their thermodynamic parameters
    Arabian Journal of Chemistry, 2014
    Co-Authors: Roya Mohammadzade Kakhki, Somayeh Heydari
    Abstract:

    Abstract A gravimetric and complexometric titration Method based on Conductometric technique is presented for the quantitative determination of brilliant green (BG) in water. The equilibrium constants and the thermodynamic parameters for the complex formation of β-cyclodextrin (β-CD) with brilliant green (BG) and precipitation of silver nitrate with BG have been determined by conductivity measurements in water. The results suggest that stable 1:1 complex is formed between BG and β-cyclodextrin and the thermodynamic parameters ( Δ H c ° , Δ S c ° ) for this complexation reaction have been determined from temperature dependence of the stability constant using the van’t Hoff plots. Based on the obtained results, the Conductometric Method for the determination of BG in the presence of β-CD at 25 °C was developed in the range of 10−8–10−3 mol L−1 and with AgNO3 is 10−3–10−5 mol L−1.

  • A thermodynamic study of complex formation between dicyclohexyl-18-crown-6 (DCH18C6) and La3+, UO22+, Ag+, and NH4+ cations in acetonitrile-tetrahydrofuran binary media using Conductometric Method
    Russian Journal of Coordination Chemistry, 2008
    Co-Authors: Gholam Hossein Rounaghi, Somayeh Heydari
    Abstract:

    The complex formation between La3+, UO22+ Ag+, and NH4+ cations and macrocyclic ligand, dicyclohexyl-18-crown-6 (DCH18C6), was studied in acetonitrile-tetrahydrofuran (AN-THF) binary mixtures at different temperatures using the Conductometric Method. The results show that with the exception of complexation of the NH4+ cation with DCH18C6 in pure acetonitrile, the stoichiometry of all the complexes is being 1: 1 (M: L). The stability constants of the complexes were determined using a GENPLOT computer program. The nonlinear behavior which was observed for changes of log Kf of the complexes versus the composition of the mixed solvent was discussed in terms of solvent-solvent interaction in their binary solution, which results in changing the chemical and physical properties of the constituent solvents when they mix with one another and, therefore, changing the solvation capacities of the metal cations, crown ether molecules, and even the resulting complexes with changing the mixed solvent composition. The results show that the selectivity of DCH18C6 for the studied cations changes with the composition of the AN-THF binary system. The sequence of stabilities of complexes in an AN-THF binary solution (mol. % AN = 75.0) at 25°C is [(DCH18C6)La)]3+ > [(DCH18C6)UO2]2+ > [(DCH18C6)Ag]+ ∼ [(DCH18C6)NH4]+, but in the case of other binary systems of AN/THF (mol. % AN = 25.0 and 50.0) is [(DCH18C6)La]+ > [(DCH18C6)NH4]+ ∼ [DCH18C6)UO2]2+ > [(DCH18C6)Ag]+.

  • a thermodynamic study of complex formation between dicyclohexyl 18 crown 6 dch18c6 and la3 uo22 ag and nh4 cations in acetonitrile tetrahydrofuran binary media using Conductometric Method
    Russian Journal of Coordination Chemistry, 2008
    Co-Authors: Gholam Hossein Rounaghi, Somayeh Heydari
    Abstract:

    The complex formation between La3+, UO22+ Ag+, and NH4+ cations and macrocyclic ligand, dicyclohexyl-18-crown-6 (DCH18C6), was studied in acetonitrile-tetrahydrofuran (AN-THF) binary mixtures at different temperatures using the Conductometric Method. The results show that with the exception of complexation of the NH4+ cation with DCH18C6 in pure acetonitrile, the stoichiometry of all the complexes is being 1: 1 (M: L). The stability constants of the complexes were determined using a GENPLOT computer program. The nonlinear behavior which was observed for changes of log Kf of the complexes versus the composition of the mixed solvent was discussed in terms of solvent-solvent interaction in their binary solution, which results in changing the chemical and physical properties of the constituent solvents when they mix with one another and, therefore, changing the solvation capacities of the metal cations, crown ether molecules, and even the resulting complexes with changing the mixed solvent composition. The results show that the selectivity of DCH18C6 for the studied cations changes with the composition of the AN-THF binary system. The sequence of stabilities of complexes in an AN-THF binary solution (mol. % AN = 75.0) at 25°C is [(DCH18C6)La)]3+ > [(DCH18C6)UO2]2+ > [(DCH18C6)Ag]+ ∼ [(DCH18C6)NH4]+, but in the case of other binary systems of AN/THF (mol. % AN = 25.0 and 50.0) is [(DCH18C6)La]+ > [(DCH18C6)NH4]+ ∼ [DCH18C6)UO2]2+ > [(DCH18C6)Ag]+.

Uwe T. Bornscheuer - One of the best experts on this subject based on the ideXlab platform.

  • Conductometric Method for the rapid characterization of the substrate specificity of amine-transaminases.
    Analytical chemistry, 2010
    Co-Authors: Sebastian Schätzle, Matthias Höhne, Karen Robins, Uwe T. Bornscheuer
    Abstract:

    Amine-transaminases (ATAs, ω-transaminases, ω-TA) are PLP-dependent enzymes that catalyze amino group transfer reactions. In contrast to the widespread and well-known amino acid-transaminases, ATAs are able to convert substrates lacking an α-carboxylic functional group. They have gained increased attention because of their potential for the asymmetric synthesis of optically active amines, which are frequently used as building blocks for the preparation of numerous pharmaceuticals. Having already introduced a fast kinetic assay based on the conversion of the model substrate α-methylbenzylamine for the characterization of the amino acceptor specificity, we now report on a kinetic conductivity assay for investigating the amino donor specificity of a given ATA. The course of an ATA-catalyzed reaction can be followed Conductometrically since the conducting substrates, a positively charged amine and a negatively charged keto acid, are converted to nonconducting products, a noncharged ketone and a zwitterionic a...

  • Conductometric Method for the rapid characterization of the substrate specificity of amine transaminases
    Analytical Chemistry, 2010
    Co-Authors: Sebastian Schätzle, Matthias Höhne, Karen Robins, Uwe T. Bornscheuer
    Abstract:

    Amine-transaminases (ATAs, omega-transaminases, omega-TA) are PLP-dependent enzymes that catalyze amino group transfer reactions. In contrast to the widespread and well-known amino acid-transaminases, ATAs are able to convert substrates lacking an alpha-carboxylic functional group. They have gained increased attention because of their potential for the asymmetric synthesis of optically active amines, which are frequently used as building blocks for the preparation of numerous pharmaceuticals. Having already introduced a fast kinetic assay based on the conversion of the model substrate alpha-methylbenzylamine for the characterization of the amino acceptor specificity, we now report on a kinetic conductivity assay for investigating the amino donor specificity of a given ATA. The course of an ATA-catalyzed reaction can be followed Conductometrically since the conducting substrates, a positively charged amine and a negatively charged keto acid, are converted to nonconducting products, a noncharged ketone and a zwitterionic amino acid. The decrease of conductivity for the investigated reaction systems were determined to be 33-52 microS mM(-1). In contrast to other ATA-assays previously described, with this approach all transamination reactions between any amine and any keto acid can be monitored without the need for an additional enzyme or staining solutions. The assay was used for the characterization of a ATA from Rhodobacter sphaeroides, and the data obtained were in excellent agreement with gas chromatography analysis.

Sebastian Schätzle - One of the best experts on this subject based on the ideXlab platform.

  • Conductometric Method for the rapid characterization of the substrate specificity of amine-transaminases.
    Analytical chemistry, 2010
    Co-Authors: Sebastian Schätzle, Matthias Höhne, Karen Robins, Uwe T. Bornscheuer
    Abstract:

    Amine-transaminases (ATAs, ω-transaminases, ω-TA) are PLP-dependent enzymes that catalyze amino group transfer reactions. In contrast to the widespread and well-known amino acid-transaminases, ATAs are able to convert substrates lacking an α-carboxylic functional group. They have gained increased attention because of their potential for the asymmetric synthesis of optically active amines, which are frequently used as building blocks for the preparation of numerous pharmaceuticals. Having already introduced a fast kinetic assay based on the conversion of the model substrate α-methylbenzylamine for the characterization of the amino acceptor specificity, we now report on a kinetic conductivity assay for investigating the amino donor specificity of a given ATA. The course of an ATA-catalyzed reaction can be followed Conductometrically since the conducting substrates, a positively charged amine and a negatively charged keto acid, are converted to nonconducting products, a noncharged ketone and a zwitterionic a...

  • Conductometric Method for the rapid characterization of the substrate specificity of amine transaminases
    Analytical Chemistry, 2010
    Co-Authors: Sebastian Schätzle, Matthias Höhne, Karen Robins, Uwe T. Bornscheuer
    Abstract:

    Amine-transaminases (ATAs, omega-transaminases, omega-TA) are PLP-dependent enzymes that catalyze amino group transfer reactions. In contrast to the widespread and well-known amino acid-transaminases, ATAs are able to convert substrates lacking an alpha-carboxylic functional group. They have gained increased attention because of their potential for the asymmetric synthesis of optically active amines, which are frequently used as building blocks for the preparation of numerous pharmaceuticals. Having already introduced a fast kinetic assay based on the conversion of the model substrate alpha-methylbenzylamine for the characterization of the amino acceptor specificity, we now report on a kinetic conductivity assay for investigating the amino donor specificity of a given ATA. The course of an ATA-catalyzed reaction can be followed Conductometrically since the conducting substrates, a positively charged amine and a negatively charged keto acid, are converted to nonconducting products, a noncharged ketone and a zwitterionic amino acid. The decrease of conductivity for the investigated reaction systems were determined to be 33-52 microS mM(-1). In contrast to other ATA-assays previously described, with this approach all transamination reactions between any amine and any keto acid can be monitored without the need for an additional enzyme or staining solutions. The assay was used for the characterization of a ATA from Rhodobacter sphaeroides, and the data obtained were in excellent agreement with gas chromatography analysis.

Razieh Sanavi Khoshnood - One of the best experts on this subject based on the ideXlab platform.

  • Study of Kryptofix5 Complexation with La 3+ Cation in Several Individual and Binary Nonaqueous Solvents Using Conductometric Method
    Russian Journal of Physical Chemistry A, 2017
    Co-Authors: Setareh Akbari, Razieh Sanavi Khoshnood, Elaheh Hatami
    Abstract:

    Complexatio of the La3+ cation with 1,13-bis(8-quinolyl)-1,4,7,10,13-pentaoxatridecane(Kryptofix5) was studied in pure solvents acetonitrile (AN), methanol (MeOH), nitrobenzene (NB), tetrahydrofuran (THF), methyl acetate (MeOAC) and in various binary solvent mixtures of AN–MeOH, AN–NB, AN–THF, and AN–MeOAC systems at different temperatures using the Conductometric Method. The stoichiometry of the complex was found to be 1 : 1 (ML). In all cases, the variation of the log kf with composition of the solvent was non-linear. This behavior is probably due to a change in the structure of these binary mixed solvents as the composition of the medium is varied. The stability order of the complex in pure nonaqueous solvents at 25°C increases in the order: AN > THF > MeOAC > MeOH > NB. The values of thermodynamic data (ΔH c °,ΔS c °) formation of (Kryptofix5.La)3+ complex are definitely solvent dependent.

  • Thermodynamic study of complex formation between Kryptofix-5 and Sn^2+ in several individual and binary non-aqueous solvents using a Conductometric Method
    Russian Journal of Physical Chemistry A, 2014
    Co-Authors: Razieh Sanavi Khoshnood, Elaheh Hatami
    Abstract:

    The complex formation between 1,13-bis(8-quinolyl)-1,4,7,10,13-pentaoxatridecane (Kryptofix-5) and Sn^2+ ions was studied in pure acetonitrile (AN), dimethylformamide (DMF), 1,4-dioxane (DOX), and methanol (MeOH) and in acetonitrile-1,4-dioxane (AN-DOX), acetonitrile-dichloromethane (AN-DCM), acetonitrile-methanol (AN-MeOH), and acetonitrile-dimethylformamide (AN-DMF) binary mixed solvent solutions at different temperatures using Conductometric Method. 1: 1 [ML] complex is formed between the metal cation and ligand in most solvent systems but in the cases of AN-MeOH (MeOH = 90 mol %) binary mixture and in pure MeOH a 2: 1 [M_2L] complex was observed, that is the stoichiometry of complexes may be changed by the nature of the medium. The stability order of the (Kryptofix-5·Sn)^2+ complex in the studied binary mixed solvent solutions at 25°C was found to be AN-DOX > AN-DCM > AN-MeOH > AN-DMF and in the case of pure solvents at 25°C the sequence was the following: AN > DMF > DOX. A non-linear behavior was observed for changes of log K _f of (Kryptofix-5·Sn)^2+ complex versus the composition of the binary mixed solvents, which was explained in terms of solvent-solvent intractions and also by the preferential solvation of the f species involved in the complexation reaction. The values of standard enthalpy changes (Δ H _ c ^○ ) for complexation reactions were obtained from the slope of the Van’t Hoff plots and the changes in standard entropy (Δ S _ c ^○ ) were calculated from the relationship Δ G _ c , 298.15 ^○ = Δ H _ c ^○ − 298.15Δ S _ c ^○ . The results show that in most cases, the (Kryptofix-5·Sn)^2+ complex is both enthalpy and entropy stabilized.

  • A Thermodynamic Study of Complex Formation Between 18-Crown-6 with T1+, Hg2+ and Ag+ Metal Cations in Some Binary Mixed Non-aqueous Solvents Using the Conductometric Method
    Journal of Inclusion Phenomena and Macrocyclic Chemistry, 2003
    Co-Authors: Gholam Hossein Rounaghi, Mohammad Hossein Arbab Zavvar, Fatemeh Boosaeedi, Razieh Sanavi Khoshnood
    Abstract:

    The complexation reactions betweenT1+, Hg2+ andAg+ metal cations with 18-Crown-6 (18C6)were studied in acetonitrile (AN)-methanol (MeOH) andbenzonitrile (BN)-methanol (MeOH) binary mixtures at differenttemperatures using the Conductometric Method. The conductance datashow that the stoichiometry of the complexes in most cases is1 : 1 (ML), but in the case of theTl+ cation, in addition to a1 : 1 complex, a 1 : 2 (ML2)complex is formed in solutions. A non-linear behaviourwas observed for the variation of log Kfof the complexes vs the composition of the binary mixed solvents. The stability of 18C6 complexes with T1+, Hg2+ and Ag+ cations is sensitive to solvent composition and in some cases, the stability order is changed with changingthe composition of the mixed solvents. The values of the thermodynamic parameters (Δ Hc°, Δ Sc°) for formation of 18C6-T1+, 18C6-Hg+2 and the 18C6-Ag+ complexes were obtained from the temperature dependence of the stability constants and the results show that the thermodynamics of the complexationreactions is affected by the nature and composition of the mixed solvents and in most cases, the complexes are enthalpy destabilized but entropy stabilized.

  • a thermodynamic study of complex formation between 18 crown 6 with t1 hg2 and ag metal cations in some binary mixed non aqueous solvents using the Conductometric Method
    Journal of Inclusion Phenomena and Macrocyclic Chemistry, 2003
    Co-Authors: Gholam Hossein Rounaghi, Mohammad Hossein Arbab Zavvar, Fatemeh Boosaeedi, Razieh Sanavi Khoshnood
    Abstract:

    The complexation reactions betweenT1+, Hg2+ andAg+ metal cations with 18-Crown-6 (18C6)were studied in acetonitrile (AN)-methanol (MeOH) andbenzonitrile (BN)-methanol (MeOH) binary mixtures at differenttemperatures using the Conductometric Method. The conductance datashow that the stoichiometry of the complexes in most cases is1 : 1 (ML), but in the case of theTl+ cation, in addition to a1 : 1 complex, a 1 : 2 (ML2)complex is formed in solutions. A non-linear behaviourwas observed for the variation of log Kfof the complexes vs the composition of the binary mixed solvents. The stability of 18C6 complexes with T1+, Hg2+ and Ag+ cations is sensitive to solvent composition and in some cases, the stability order is changed with changingthe composition of the mixed solvents. The values of the thermodynamic parameters (Δ Hc°, Δ Sc°) for formation of 18C6-T1+, 18C6-Hg+2 and the 18C6-Ag+ complexes were obtained from the temperature dependence of the stability constants and the results show that the thermodynamics of the complexationreactions is affected by the nature and composition of the mixed solvents and in most cases, the complexes are enthalpy destabilized but entropy stabilized.

  • A Thermodynamic Study of Complex Formation Between 18-Crown-6 with T1^ + , Hg^ 2+ and Ag^ + Metal Cations in Some Binary Mixed Non-aqueous Solvents Using the
    Journal of inclusion phenomena and macrocyclic chemistry, 2003
    Co-Authors: Gholam Hossein Rounaghi, Mohammad Hossein Arbab Zavvar, Fatemeh Boosaeedi, Razieh Sanavi Khoshnood
    Abstract:

    The complexation reactions betweenT1^+, Hg^2+ andAg^+ metal cations with 18-Crown-6 (18C6)were studied in acetonitrile (AN)-methanol (MeOH) andbenzonitrile (BN)-methanol (MeOH) binary mixtures at differenttemperatures using the Conductometric Method. The conductance datashow that the stoichiometry of the complexes in most cases is1 : 1 (ML), but in the case of theTl^+ cation, in addition to a1 : 1 complex, a 1 : 2 (ML_2)complex is formed in solutions. A non-linear behaviourwas observed for the variation of log K_fof the complexes vs the composition of the binary mixed solvents. The stability of 18C6 complexes with T1^+, Hg^2+ and Ag^+ cations is sensitive to solvent composition and in some cases, the stability order is changed with changingthe composition of the mixed solvents. The values of the thermodynamic parameters (Δ H_c°, Δ S_c°) for formation of 18C6-T1^+, 18C6-Hg^+2 and the 18C6-Ag^+ complexes were obtained from the temperature dependence of the stability constants and the results show that the thermodynamics of the complexationreactions is affected by the nature and composition of the mixed solvents and in most cases, the complexes are enthalpy destabilized but entropy stabilized.