Complexation study of cryptand 222 with lanthanum(III) cation in binary mixed non-aqueous solvents

Conductometric titrations have been performed in some binary solvent solutions of acetonitrile (AN), 1,2-dichloroethane (DCE), ethylacetate (EtOAc) and methylacetate (MeOAc) with methanol (MeOH), at 288, 298, 308, and 318 K to give the complex stability constant and the thermodynamic parameters for the complexation of lanthanum(III) cation with 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]-hexacosane (cryptand 222). The stability constant of the resulting 1:1 complex at each temperature was determined from computer fitting of the conductance-mole ratio data. The results revealed that, the stoichiometry and the stability order of (cryptand 222 · La)³⁺ complex changes with the nature and also the composition of the solvent system. A non-linear relationship was observed between the stability constant (logK _f) of (cryptand 222 · La)³⁺ complex versus the composition of the binary mixed solvents. Thermodynamically, the complexation of lanthanum(III) cation with the cryptand 222, is mainly entropy governed and the values of these parameters are influenced by the nature and composition of the binary mixed solvent solutions.     

Effect of magnetic field on property of a non-aqueous solvent upon complex formation between kryptofix 22DD with yttrium (III) cation

To understand the effect of a magnetized solvent upon complexation processes between the metal ions and the ligands, we studied the complexation reaction between Y⁺³ cation with the kryptofix 22DD, in non-magnetized and magnetized methanol solvents at different temperatures using the conductometric method. Addition of kryptofix 22DD to the cation solution causes a continuous increase in the molar conductivities which indicates that the mobility of the complexed cation is higher than the uncomplexed one in both non-magnetized and magnetized methanol solvents. The conductance data show that the stoichiometry of the complex formed between the ligand and Y³⁺ cation is 1:1(M:L). The value of stability constant of (kryptofix 22DD.Y)³⁺ complex was determined from conductometric data using a non-linear least-square program (GENPLOT). The results obtained in this investigation, show that the stability constant of the complex decreases when we use magnetized methanol solvent.     

A conductometric study of complexation reaction between dibenzo-24-crown-8 with yttrium cation in some binary mixed non-aqueous solvents

The complexation reaction of macrocyclic ligand, dibenzo-24-crown-8 (DB24C8) with Y⁺³ cation was studied in some binary mixtures of methanol (MeOH), ethanol (EtOH), acetonitrile (AN) and tetrahydrofuran (THF) with dimethylformamide (DMF) at different temperatures using the conductometric method. The conductance data show that in all solvent systems, the stoichiometry of the complex formed between DB24C8 and Y⁺³ cation is 1:1 (ML). The stability order of (DB24C8.Y)⁺³ complex in pure non-aqueous solvents was found to be: AN > EtOH > MeOH > DMF. A non-linear behaviour was observed for changes of log K_f of (DB24C8.Y)⁺³ complex versus the composition of the binary mixed solvents, which was explained in terms of solvent–solvent interactions and also the heteroselective solvation of the species involved in the complexation reaction. The obtained results show that the stability of (DB24C8.Y)⁺³ complex is sensitive to the mixed solvents composition. The values of thermodynamic parameters (?H°_c and ?S°_c) for formation of (DB24C8.Y)⁺³ complex were obtained from temperature dependence of the stability constant using the van’t Hoff plots. The results show that in most cases, the (DB24C8.Y)⁺³ complex is enthalpy destabilized but entropy stabilized and the values and also the sign of thermodynamic parameters are influenced by the nature and composition of the mixed solvents.     

Complexation study of dibenzo-18-crown-6 with UO2 2+ cation in binary mixed non-aqueous solutions

The complexation reaction of macrocyclic ligand, dibenzo-18-crown-6 (DB18C6) with UO₂ ²⁺ cation was studied in ethylacetate-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 the stoichiometry of the complex formed between DB18C6 and UO₂ ²⁺ cation is affected by the nature of the solvent systems. A non-linear behaviour was observed for changes of log K _f of (DB18C6.UO₂)⁺² complex versus the composition of the binary mixed solvents. The values of thermodynamic quantities (?S°_c, ?H°_c) for formation of (DB18C6.UO₂)⁺² complex were obtained from temperature dependence of the stability constant using the van’t Hoff plots. The results show that in most cases, the complex is enthalpy stabilized and in all cases entropy stabilized and both parameters are affected by the nature and composition of the mixed solvents. In addition, the complex formation between dicyclohexyl-18-crown-6 (DCH18C6) and UO₂ ²⁺ cation was studied in pure AN and the results were compared with those of the (DB18C6.UO₂)⁺² complex.     

Effect of solvent on complexation between Y3+ cation and 4,13-diaza-18-crown-6 in some binary mixed non-aqueous solvents

The complexation reaction of 4,13-diaza-18-crown-6 (DA18C6) with Y³⁺ cation was studied in some binary mixed solvent solutions of acetonitrile (AN) with methanol (MeOH), ethanol (EtOH), 2-propanol (2-PrOH) and methyl acetate (MeOAc) at different temperatures by conductometric method. The obtained data show that in all studied solutions the stoichiometry of the complex formed between DA18C6 and Y³⁺ cation is 1: 1 [ML], but in the case of pure MeOAc, a 2: 1 [ML₂] complex is formed in solution upon addition of the ligand to the metal salt solution, and further addition of the ligand results in formation of a M₂L₂ complex in solution. This results show that the stoichiometry of the composition of the macrocyclic complexes may be affected by the nature of the solvent system. The results obtained in this study show that the stability constant of the resulting 1: 1 [ML] complex in the binary solvent solutions decreases in the order: AN-MeOAc > AN-2PrOH > AN-MeOH > AN-EtOH. A non-linear relationship was observed between the stability constant (logK _f ) of [Y(DA18C6)]³⁺ complex with the composition of the binary mixed solvent solutions. The corresponding standard thermodynamic parameters (H° _c , Δ S° _c ) for 1: 1 [ML] complexation reaction between DA18C6 and Y³⁺ cation were obtained from temperature dependence of the stability constant of the complex. The results show that, in all solvent systems, the (DAI8C6.Y)³⁺ complex is entropy stabilized, but from enthalpy point of view, depending on the solvent system, it is stabilized or destabilized and the result show that the values of both thermodynamic quantities change with the nature and composition of the binary mixed solvent solutions.     

Solvent influence upon complexation of N-phenylaza-15-crown-5 with UO2 2+ cation in binary mixed non-aqueous solvents

The complexation reaction of N-phenylaza-15-crown-5 (PhA15C5) with UO₂ ²⁺ cation was studied in acetonitrile–methanol (AN–MeOH), acetonitrile–butanol (AN–BuOH), acetonitrile–dimethylformamide (AN–DMF) and methanol–propylencarbonate (MeOH–PC) binary solutions, at different temperatures by conductometry method. The conductance data show that the stoichiometry of the complex formed between PhA15C5 with UO₂ ²⁺ cation in most cases is 1:1 [M:L], but in some solvent systems a 1:2 [M:L₂] complex is formed in solutions. The results revealed that, the stability constant of (PhA15C5·UO₂)²⁺ complex in the binary mixed solvents varies in the order: AN–BuOH>AN–MeOH>AN–DMF. In the case of the pure organic solvents, the sequence of the stability of the complex changes as: AN>PC>BuOH>DMF. A non-linear relationship was observed for changes of logK_f of (PhA15C5·UO₂)²⁺ complex versus the composition of the binary mixed solvents. The corresponding standard thermodynamic parameters (ΔH_c°, ΔS_c°) were obtained from temperature dependence of the stability constant. The results show that the values and also the sign of these parameters are influenced by the nature and composition of the mixed solvents.     

Study of complex formation between dicyclohexyl-18-crown-6 and UO2 2+ cation in some binary mixed non-aqueous solvents using conductometric method

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.     

Study of complex formation between 18-crown-6 and diaza-18-crown-6 with uranyl cation (UO2 2+) in some binary mixed aqueous and non-aqueous solvents

The complexation reaction between UO₂ ²⁺ cation with macrocyclic ligand, 18-crown-6 (18C6), was studied in acetonitrile–methanol (AN–MeOH), nitromethane–methanol (NM–MeOH) and propylencarbonate–ethanol (PC–EtOH) binary mixed systems at 25 °C. In addition, the complexation process between UO₂ ²⁺ cation with diaza-18-crown-6 (DA18C6) was studied in acetonitrile–methanol (AN–MeOH), acetonitrile–ethanol (AN–EtOH), acetonitrile–ethylacetate (AN–EtOAc), methanol–water (MeOH–H₂O), ethanol–water (EtOH–H₂O), acetonitrile–water (AN–H₂O), dimethylformamide–methanol (DMF–MeOH), dimethylformamide–ethanol (DMF–EtOH), and dimethylformamide–ethylacetate (DMF–EtOAc) binary solutions at 25 °C using the conductometric method. The conductance data show that the stoichiometry of the complexes formed between (18C6) and (DA18C6) with UO₂ ²⁺ cation in most cases is 1:1 [M:L], but in some solvent 1:2 [M:L₂] complex is formed in solutions. The values of stability constants (log K_f) of (18C6 · UO₂ ²⁺) and (DA18C6 · UO₂ ²⁺) complexes which were obtained from conductometric data, show that the nature and also the composition of the solvent systems are important factors that are effective on the stability and even the stoichiometry of the complexes formed in solutions. In all cases, a non-linear relationship is observed for the changes of stability constants (log K_f) of the (18C6 · UO₂ ²⁺) and (DA18C6 · UO₂ ²⁺) complexes versus the composition of the binary mixed solvents. The stability order of (18C6 · UO₂ ²⁺) complex in pure studied solvents was found to be: EtOH > AN ≈ NM > PC ≈ MeOH, but in the case of (DA18C6 · UO₂ ²⁺) complex it was : H₂O > MeOH > EtOH.     

Solvent influence upon complex formation between different 1,8-dioxo-octahydroxanthene derivatives and yttrium(III) cation in some non-aqueous solvents using conductometric method

The complexation reactions between the yttrium(III) cation and (4-chlorophenyl, phenyl, 4-nitrophenyl, 4-methoxyphenyl, 4-methylphenyl) 9-substituted 1,8-dioxo-octahydroxanthene were studied in acetonitrile (AN) and methanol (MeOH) at different temperatures using the electrical conductivity measurements. The conductance data show that the stoichiometry of all formed complexes between the Y³⁺ cation and the studied ligands is 1: 1 [ML]. The order of stability of the complexes formed between the organic ligands and Y³⁺ cation in pure MeOH at 45°C was found to be: (3,6,6-Tetramethyl-9-(4-chlorophenyl)-1,8- dioxo-octahydroxanthene·Y³⁺) > (3,6,6-Tetramethyl-9-(4-methoxyphenyl)-1,8-dioxo-octahydroxanthene · Y³⁺) > (3,6,6-Tetramethyl-9-(4-phenyl)-1,8-dioxo-octahydroxanthene·Y³⁺) ≈ (3,6,6-Tetramethyl-9-(4- nitrophenyl)-1,8-dioxo-octahydroxanthene·Y³⁺) > (3,6,6-Tetramethyl-9-(4-methylphenyl)-1,8-dioxooctahydroxanthene ·Y³⁺). The values of the standard thermodynamic parameters (ΔH_c^°, ΔS_c^°) for formation of the complexes were obtained from temperature dependence of the formation constants of the complexes using the van’t Hoff plots. The experimental results show that the thermodynamics of the complexation reactions is influenced by the nature of solvent system and in most cases, the complexes are entropy stabilized.     

Thermodynamics of ZrO2+ cation complexation with dibenzo-18-crown-6 in mixed non-aqueous solvents

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?K_f of (DB18C6·ZrO)²⁺ complex versus the composition of the binary mixed solvents. The corresponding standard thermodynamic parameters (ΔH _c ^° , ΔS _c ^° ) 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.     

Phase diagrams of liquid-crystal binary systems of lanthanum(III) laurate with some divalent metal laurates

Phase equilibria in binary systems of lanthanum(III) laurate with laurates of divalent metals (lead, cadmium, zinc, and cobalt) are studied at temperatures from 0 to 350°C using differential thermal analysis (DTA) and polythermal polarized-light microscopy. Continuous or terminal smectic A liquid-crystal (LC) solutions are found to form in all systems. The temperature-concentration fields of formation of ionic LCs and glasses are determined.     

Thermal and X-ray diffraction investigations of some lanthanum(III) and neodymium(III) oxide-alkali persulfate binary systems

Different molar ratios of La₂O₃ or Nd₂O₃:Na₂/K₂S₂O₈ have been prepared, and the results of their TG and DTA investigations, under an atmosphere of static air, are reported. The effects of either La₂O₃ or Nd₂O₃ on the thermal decomposition of the persulfates from ambient to 1050°C, using a derivatograph, have been studied. It has been found that La₂O₃ lowers the initial decomposition temperatures of these alkali persulfates through catalytic activity. Nd₂O₃ shows little or no catalytic effect and therefore it acts as an insulator. Intermediate and final products are identified by X-ray diffraction analysis. The stoichiometric molar ratios of the solid state reactions are 1:3::R₂O₃:M₂S₂O₈. (R = La or Nd. M = Na or K), which give double salts of formulae: NaLa(So₄)₂, KLa(SO₄)₂, NaNd(SO₄)₂, and KNd(SO₄)₂. No sulfates or oxysulfates of lanthanum or neodymium have been identified.     

Study of complexation process between N-phenylaza-15-crown-5 with yttrium cation in binary mixed solvents

The complexation reaction between Y³⁺ cation with N-phenylaza-15-crown-5(Ph-N15C5) was studied at different temperatures in acetonitrile–methanol (AN/MeOH), acetonitrile–propanol (AN/PrOH), acetonitrile–1,2 dichloroethane (AN/DCE) and acetonitrile–water (AN/H₂O) binary mixtures using the conductometric method. The results show that in all cases, the stoichiometry of the complex is 1:1 (ML). The values of formation constant of the complex which were determined using conductometric data, show that the stability of (Ph-N15C5.Y)³⁺ complex in pure solvents at 25?°C changes in the following order: PrOH?>?AN?>?MeOH and in the case of binary mixed solutions at 25?°C it follows the order: AN–DCE?>?AN–PrOH?>?AN–MeOH?>?AN–H₂O. The values of standard thermodynamic quantities (?H _c ^° and ?S _c ^° ) for formation of (Ph-N15C5.Y)³⁺ complex were obtained from temperature dependence of the formation constant using the van’t Hoff plots. The results show that in most cases, the complex is entropy and enthalpy stabilized and these parameters are influenced by the nature and composition of the mixed solvents. In most cases, a non-linear behavior was observed for variation of log K_f of the complex versus the composition of the binary mixed solvents. In all cases, an enthalpy–entropy compensation effect was observed for formation of (Ph-N15C5.Y)³⁺ complex in the binary mixed solvents.     

Polarographic and voltammetric studies of tetrabutylammonium hexacyanoferrate(III) and tetrabutylammonium hexacyanomanganate(III) in non-aqueous solvents

Tetrabutylammonium hexacyanomanganate(III) [(bu₄N)₃Mn(CN)₆] has been studied by polarography and cyclic voltammetry in formamide, methanol, ethanol, N-methylformamide, dichloromethane, dimethylsulfoxide, acetonitrile, N,N-dimethylformamide, propylenecarbonate, butyrolactone, N-methylthiopyrrolidone(2), N,N-dimethylthioformamide, 1.2-dichloroethane, N-methylpyrrolidone(2) and tetramethylenesulfone. Similar studies have been carried out for tetrabutylammonium hexacyanoferrate(III) [(bu₄N)₃ Fe(CN)₆] in the solvents formamide, N-methylformamide, dichloromethane, butyrolactone, N-methylthiopyrrolidone(2) and tetramethylenesulfone. The half-wave potentials of the reductions (bu₄N)₃Mn(CN)₆ to (bu₄N)₄Mn(CN)₆ and (bu₄N)₃Fe(CN)₆ to (bu₄N)₄Fe(CN)₆ versus bisbiphenylchromium(I)/bisbiphenylchromium(0) as a reference redox system were found to vary with the nature of the solvent. Comparison with data previously obtained for the respective tetraethylammonium salts of hexacyanoferrate(III) and hexacyanomanganate(III) have shown that the redox behaviour of these compounds is influenced by both the solvent and the tetraalkylammonium ions. Correlations exist between the half-wave potentials of (bu₄N)₃Mn(CN)₆ and (bu₄N)₃Fe(CN)₆ and both the acceptor number of the solvents and the free enthalpies of transfer of the chloride ion. The results are discussed in the concept of donor-acceptor interactions.     

Complexing ability of some mixed sulfur-oxygen crown ethers in nonaqueous solvents

Complexes of the Li⁺, Na⁺, Cs⁺, Tl⁺ and Ag⁺ ion with macrocyclic ligands dithia-18-crown-6 and trithia-12-crown-4 were studied by multinuclear NMR in several nonaqueous solvents and their stabilities are compared with the complexes formed by the analogous polyethers, 18-crown-6 and 12-crown-4. In all cases the substitution of the sulfur atoms for the oxygens results in a substantial decrease in the stability of the complexes. While the stability of the macrocyclic complexes is strongly influenced by the solvents and varies inversely with the Gutmann's donicity scale for these solvents, the decrease in the stability of the thia-complexes is only marginally dependent on the solvent properties but varies significantly with the cation, being largest for the Cs⁺ ion.     

Electronic absorption spectra of some azo compounds with condensed ring systems in non-aqueous and mixed buffer solvents

The electronic absorption spectra of eight substituted phenylazo derivatives of α-and β-naphthol, 9-phenanthrol and 5- and 6-chrysenol were studied in different organic solvents. The assignment of the spectral bands obtained and also the effect of organic solvents on the colour of the compounds was investigated. The spectra in buffer solution over the pH range 2–14 were recorded and explained; also the pK_a values were determined.     

Complexation of americium(III) with humic acid by cation exchange and solvent extraction

Complexation of Am(III) with humic acid was studied at various pHs in 0.1M NaClO₄. The stability constants of the Am(III)—humate complexes were determined by a cation-exchange method. The values of log₁ and log₂ increased slightly with increases of pH from 4 to 6 and were found to be 6.9 and 11.6, respectively, at a pH of 5. Markedly larger values than these were obtained by a solvent extraction method. This discrepancy was also revealed by summarizing data from several literature sources. It is very likely that this can be ascribed to decreases in either humic acid and/or the extractant from the extraction system due to humate interactions at the aqueous-organic interface.This revised version was published online in November 2005 with corrections to the Cover Date.