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The extraction of lithium from aqueous solutions of LiNTf2 and LiCl salts using benzo-15-crown-5 ether (B15C5) as an extractant in [C8mim][NTf2] ionic liquid was studied. The transition of the extractant into the aqueous phase and the distribution of Cl− ions during lithium extraction from LiCl solutions were determined. LiNTf2 complexes with B15C5 with different LiNTf2:B15C5 ratios were isolated for the first time and characterized via X-ray diffraction and IR spectroscopy. Differences in the extraction process of LiCl and LiNTf2 were determined via an infrared spectroscopic study of the extraction systems. [ABSTRACT FROM AUTHOR]

Abstract: A series of novel (oligo)thienyl-imidazo-benzocrown ethers were synthesised through a simple method and evaluated as fluorimetric chemosensors for transition metal cations. Interaction with Ni2+, Pd2+, and Hg2+ in ACN/DMSO solution (99:1) was studied by absorption and emission spectroscopy. Chemoselectivity studies in the presence of Na+ were also carried out and a fluorescence enhancement upon chelation (CHEF) effect was observed following Hg2+ complexation. Considering that most systems using fluorescence spectroscopy for detecting Hg2+ are based on the complexation enhancement of the fluorescence quenching (CHEQ) effect, the present work represents one of the few examples for sensing of Hg2+ based on a CHEF effect. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]

Novel photosignal transduction systems of benzo-15-crown-5 (B15C5) azoprobe/γ-cyclodextrin (γ-CyD) complexes were designed. Four B15C5 azoprobes were synthesized by azo coupling of 4'-aminobenzo-15-crown-5 with phenol (for 15C5-Az-Ph) and N,N-dialkylanilines (for 15C5-Az-Cn). These azoprobes exhibited strong induced circular dichroism (ICD) by forming an inclusion complex with γ-CyD. Examination of the spectral responses and 1H NMR analysis of the B15C5 azoprobe/γ-CyD complexes in the presence of alkali metal cations revealed that K+ binding selectively induced dimer formation of the B15C5 azoprobes inside the γ-CyD cavity, which resulted in distinct changes in their UV-vis and ICD spectra in water. The effect of alkyl chain length of 15C5-Az-Cn (n= 1, 2, 4)/γ-CyD complexes was examined in 90% H2O/10% CH3CN (v/v). The highest K+ ion response was noted for the 15C5-Az-C2/γ-CyD complex. The 15C5-Az-C4/γ-CyD complex was found to show abnormally high ICD responses for TMA+ and Cs+. [ABSTRACT FROM AUTHOR]

Abstract: The thermodynamic functions of complex formation of benzo-15-crown-5 ether with sodium cation in {(1−x)DMA+xH2O} 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+xH2O} is discussed. [Copyright &y& Elsevier]

Enthalpy of solution of crown ethers (15-crown-5 and benzo-15-crown-5) in water–acetone mixtures have been measured within the whole range of mole fraction at 298.15 K. The obtained data have been compared with those of the solution enthalpy of both crown ethers in the mixtures of water with dimethyl sulfoxide. The replacement of &z.sbnd;S&z.dbnd6;O group with &z.sbnd;C&z.dbnd6;O in the molecule of the organic solvent brings about an increase in the exothermic effect of the solution of 15-crown-5 and benzo-15-crown-5 ethers, especially in the mixtures with a medium water content. The observed effect is connected with the preferential solvation of the molecules of both crown ethers by acetone molecules in the water–acetone mixtures. The process of preferential solvation of 15-crown-5 and benzo-15-crown-5 ethers does not take place in the water–dimethyl sulfoxide mixture. [Copyright &y& Elsevier]

The equilibrium constants of complex formation of benzo-15-crown-5 ether with sodium cation in {(1−x)DMF + xH2O} 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 + xH2O}. A good relationship between the enthalpy and entropy of complex formation was observed. [Copyright &y& Elsevier]

Enthalpies of solution of 15-crown-5 (15C5) in the mixtures of water with acetonitrile (AN) or propan-1-ol (PrOH) and benzo-15-crown-5 ether (B15C5) in the PrOH-water mixtures have been measured at 298.15 K. The values of standard enthalpies of solution of 15C5 are negative in the mixtures of water with AN within the whole range of mixture composition and in the mixtures water-PrOH for water content xw>0.1 and those of B15C5 are positive (except the standard enthalpy of B15C5 in pure water) in the system water-PrOH. The results of the calorimetric measurements together with the earlier data for B15C5 in water-acetonitrile mixtures are discussed with regard to the intermolecular interactions that occur in these systems. [ABSTRACT FROM AUTHOR]