A ratiometric chemodosimeter for highly selective naked-eye and fluorogenic detection of cyanide

A simple indole-based chemosensor (1) with a very low molecular weight of 207 g mol⁻¹ has been synthesized for the highly reactive and selective detection of CN⁻ in aqueous media, even in the presence of other anions, such as F⁻, Cl⁻, Br⁻, AcO⁻, S₂⁻${{\mathrm{S}}_2}^{-}$, SCN⁻, NO₂⁻${{\text{NO}}_2}^{-}$, NO₃⁻${{\text{NO}}_3}^{-}$, CO₃⁻${{\text{CO}}_3}^{-}$, BzO⁻, H₂PO₄⁻${{\mathrm{H}}_2{\text{PO}}_4}^{-}$, and HSO₄⁻${{\text{HSO}}_4}^{-}$. The sensor achieves rapid detection of cyanide anion in 2 min, and the pseudo-first-order rate constant is estimated as 1.576 min⁻¹. The colorimetric and ratiometric fluorescent response of the sensor to CN⁻ is attributable to the addition of CN⁻ to the electron-deficient dicyanovinyl group of 1, which prevents intramolecular charge transfer. The sensing mechanism is supported by density functional theory and time-dependent density functional theory calculations. Moreover, sensor 1 exhibits both high accuracy in determining the concentration of CN⁻ in real samples and 1-based test strips can conveniently detect CN⁻ without any additional equipment. The detection limit of the sensor 1 (1.1 μM) for cyanide is lower than the maximum permissible level of CN⁻ (1.9 μM) in drinking water.     

A phenanthrene-based calix[4]arene as a fluorescent sensor for Cu and F

A new phenanthrene-based fluorescent calix[4]arene (4) has been synthesized in cone conformation. This compound was examined for its fluorescent properties towards different metal ions (Na⁺, Li⁺, Mg²⁺, Ni²⁺, Ba²⁺, Ca²⁺, Cu²⁺, Pb²⁺) and anions (F⁻, Cl⁻, Br⁻, H₂₄PO⁻,${{\text{H}}_2{\text{PO}}_4}^{-}\text{,}$₃NO⁻,${{\text{NO}}_3}^{-}\text{,}$₄HSO⁻,${{\text{HSO}}_4}^{-}\text{,}$ CH₃COO⁻) by fluorescence spectroscopy. The properties of the compound were evaluated and show that it is a fluorescence sensor for Cu²⁺ and F⁻. With the addition of Cu²⁺ and F⁻, the fluorescence was severely quenched.     

Dehydration performance of a hydrophobic DD3R zeolite membrane

The all silica DDR membrane turns out to be well suited to separate water from organic solvents under pervaporation conditions, despite its hydrophobic character. All-silica zeolites are chemically and hydrothermally more stable than aluminum containing ones and are therefore preferred for membrane applications, including for dehydration, even though these type of membranes are hydrophobic. Permeation of water, ethanol and methanol through an all-silica DDR membrane has been measured at temperatures ranging from 344 to 398 K. The hydrophobic membrane shows high water fluxes (up to 20 kg m⁻² h⁻¹). The pure water permeance is insensitive to temperature and is well described assuming weak adsorption. Excellent performance in dewatering ethanol (N=2$N=2$ kg m⁻² h⁻¹and _αw=1500${\alpha }_{\text{w}}=1500$ at 373 K and _xw=0.18$x_{\text{w}}=0.18$) is observed and the membrane is also able to selectively remove water from methanol (N=5$N=5$ kg m⁻² h⁻¹ and _αw=9${\alpha }_{\text{w}}=9$). Water could also be removed from methanol/ethanol/water (_αwater_/EtOH=1500${\alpha }_{\text{water}/\text{EtOH}}=1500$, _αMeOH_/EtOH=70${\alpha }_{\text{MeOH}/\text{EtOH}}=70$ at 373 K) mixtures, even at water feed concentrations below 1.5 mol%.     

Modelling LLE and VLE of methanol + n-alkane series using GC-PC-SAFT with a group contribution kij

The fluid phase diagrams (LLE and VLE) of methanol + n-alkane mixtures series (from C₄ up to C₁₆) were modelled using GC-PC-SAFT EOS (Tamouza et al., Fluid Phase Equilibria 222–223 (2004) 67–76) combined with a recent method for computing k_ij based on the London theory (NguyenHuynh et al., Industrial & Engineering Chemistry Research 47 (2008) 8847–8858). This latter method requires pure compound adjustable parameters: pseudo-ionization energies J that may be calculated by group contribution in the case of n-alkane series. J_alkane is calculated from group parameters JCH₃$J_{\text{C}{\text{H}}_3}$ and JCH₂$J_{\text{C}{\text{H}}_2}$.     

Influence of chemical effect on the K-shell X-ray production cross-sections and radiative Auger ratios of Zn complexes

In this study, _σK_α${\sigma }_{{\text{K}}_{\mathrm{\alpha }}}$, _σK_β${\sigma }_{{\text{K}}_{\mathrm{\beta }}}$ production cross-sections, KLM/K_α and KMM/K_β radiative Auger intensity ratios of Zn in different complexes were measured. The samples were excited by 59.5 keV γ-rays from a ²⁴¹Am annular radioactive source. K X-rays emitted by samples were counted by an Ultra-LEGe detector with a resolution of 150 eV at 5.9 keV. The charge transfer effects on central Zn atom was investigated by using the behaviors of different ligands in these complexes.     

Thermodynamic properties of the ternary system {yNH4Cl + (1 − y)MgCl2} (aq) at 298.15 K

The mixture {yNH₄Cl + (1 − y)MgCl₂} (aq) has been studied using the hygrometric method at the temperature 298.15 K. The water activities are measured at total molalities from 0.30 mol kg⁻¹ up to saturation for different ionic strength fractions y of NH₄Cl with y = 0.20, 0.50 and 0.80. The obtained data allow the deduction of osmotic coefficients. Experimental results are compared with the calculations using the models of Zdanovskii–Stokes–Robinson, Kusik and Meissner, Robinson and Stokes, Lietzke and Stoughton, Reilly–Wood and Robinson and Pitzer. Thermodynamic properties have been modeled using the Pitzer ion-interaction model with inclusion of an ionic strength dependence of the third virial coefficient for the binary systems. From these measurements and the obtained binary parameters β⁽⁰⁾, β⁽¹⁾, C⁽⁰⁾ and C⁽¹⁾, the mixing ionic parameters θNH₄Mg${\theta }_{\text{N}{\text{H}}_4\text{Mg}}$ and ψNH₄MgCl${\psi }_{\text{N}{\text{H}}_4\text{MgCl}}$ are determined by the standard Pitzer model. The results show that a good accuracy is obtained with the standard Pitzer model using extended binary parameters. The parameters θNH₄Mg${\theta }_{\text{N}{\text{H}}_4\text{Mg}}$ and ψNH₄MgCl${\psi }_{\text{N}{\text{H}}_4\text{MgCl}}$ were used for evaluation of activity coefficients in the mixture. The excess Gibbs energy is also determined.     

Buoyancy density measurements for 1-alkyl-3-methylimidazolium based ionic liquids with tetrafluoroborate anion

Density measurements are reported performed on three 1-alkyl-3-methylimidazolium-based ([C_n-mim], n=2,4,6$n=2\text{,}4\text{,}6$) ionic liquids with tetrafluoroborate anion at atmospheric pressure at 15 temperatures from 281 to 353 K. The buoyancy method was employed, using the microbalance of the Krüss K100MK2 tensiometer. At each temperature from 33 to 55 individual buoyancy readings were taken in most cases. The density average values at particular temperatures are presented with estimated total standard uncertainty less than ±0.4$\pm 0.4$ kg m⁻³ (3.3 ×10⁻⁴?$\times 10^{-4}?$). An empirical density–temperature equations have been developed describing the temperature dependence of each ionic liquid density. The 58 new experimental data points on the density–temperature relation of the three ionic liquids of interest are means calculated from about 3000 individual density readings, which have been altogether taken in the present study.     

Study of copper complexes in saturated and unsaturated aqueous ammonium oxalate solutions containing Cu(II) impurity

The influence of Cu(II) impurity on chemical equilibria in unsaturated and saturated ammonium oxalate (AO) aqueous solutions was investigated as a function of concentration _ci$c_{\text{i}}$ of impurity. Using the computer programme “Hyss” the species present in the solutions were analysed. It was found that in the aqueous solutions of ammonium oxalate containing Cu(II) ions the following species are formed: Cu²⁺, Cu(OH)⁺, Cu(OH)₂, CuC₂O₄⁰ and Cu(C₂O₄)₂²⁻ in addition to C₂O₄²⁻, HC₂O₄⁻, H₂C₂O₄ and (NH₄)₂C₂O₄⁰ species, and their concentration depends on concentrations _ci$c_{\text{i}}$ of Cu(II) impurity and c of ammonium oxalate. The dependences of solution pH and of absorbance A   and the corresponding wavelength λ$\lambda$ for unsaturated aqueous solutions on ammonium oxalate concentration c   containing different concentrations _ci$c_{\text{i}}$ of Cu(II) ions showed three well-defined regions characterised by transition values of solution pH or solute concentration c. Speciation analysis revealed that Cu²⁺ and CuC₂O₄⁰, CuC₂O₄⁰ and Cu(C₂O₄₎₂²⁻, and Cu(C₂O₄)₂²⁻ complexes are predominantly present in the solute concentration intervals c≤0.01$c\le 0.01$ mol/dm³, 0.01 mol/dm³ <c<0.03$<c<0.03$ mol/dm³ and c≥0.03$c\ge 0.03$ mol/dm³, respectively. The concentration interval range 0.01 mol/dm³ <c<0.03$<c<0.03$ mol/dm³ corresponds to the pH interval where Cu(OH)₂ is precipitated. It was found that the solubility of ammonium oxalate at 30 °$°$C increases practically linearly with an increase in the concentration of Cu(II) impurity. Speciation analysis of saturated aqueous solutions of ammonium oxalate revealed that Cu(II) ions contained in AO saturated solutions exist mainly as Cu(C₂O₄)₂²⁻-type complexes, and the increase in the solubility of AO in the presence of Cu(II) impurity is essentially due to an increase in the ratio of the concentrations of CuC₂O₄⁰ and Cu(C₂O₄)₂²⁻ species.     

Solubility of carbon dioxide in the solvent system (2-amino-2-methyl-1-propanol + sulfolane + water)

New sets of data for the solubility of CO₂ in the amine solvent system of 2-amino-2-methyl-1-propanol (1) + sulfolane (2) + water (3) were presented in this work. The measurements were done at temperatures of 313.2, 333.2, 353.2, and 373.2 K and CO₂ partial pressures up to 193 kPa. The investigated compositions were as follows: (i) w₁=16.5%$w_1=16.5\%$, w₂=32.2%$w_2=32.2\%$; (ii) w₁=8.2%$w_1=8.2\%$, w₂=41.2%$w_2=41.2\%$; (iii) w₁=22.3%$w_1=22.3\%$, w₂=27.7%$w_2=27.7\%$; and (iv) w₁=30.6%$w_1=30.6\%$, w₂=19.4%$w_2=19.4\%$, where w$w$ is the mass percent of the component. The present solubility data was correlated by a modified Kent–Eisenberg model. The model reasonably represents the present solubility data, not only over the considered conditions, but also for a wider range of temperatures, partial pressures, and compositions.     

Characterization of Ascentis RP-Amide column: Lipophilicity measurement and linear solvation energy relationships

This study investigates lipophilicity determination by chromatographic measurements using the polar embedded Ascentis RP-Amide stationary phase. As a new generation of amide-functionalized silica stationary phase, the Ascentis RP-Amide column is evaluated as a possible substitution to the n  -octanol/water partitioning system for lipophilicity measurements. For this evaluation, extrapolated retention factors, log k^′_w$\text{log}{k^{\prime }}_w$, of a set of diverse compounds were determined using different methanol contents in the mobile phase. The use of n-octanol enriched mobile phase enhances the relationship between the slope (S  ) of the extrapolation lines and the extrapolated log k^′_w$\text{log}{k^{\prime }}_w$ (the intercept of the extrapolation), as well as the correlation between log P   values and the extrapolated log k^′_w$\text{log}{k^{\prime }}_w$ (1:1 correlation, r² = 0.966). In addition, the use of isocratic retention factors, at 40% methanol in the mobile phase, provides a rapid tool for lipophilicity determination. The intermolecular interactions that contribute to the retention process in the Ascentis RP-Amide phase are characterized using the solvation parameter model of Abraham. The LSER system constants for the column are very similar to the LSER constants of the n-octanol/water extraction system. Tanaka radar plots are used for quick visual comparison of the system constants of the Ascentis RP-Amide column and the n-octanol/water extraction system. The results all indicate that the Ascentis RP-Amide stationary phase can provide reliable lipophilic data.     

Synthesis,photophysical and photochemical studies of water soluble cationic zinc phthalocyanine derivatives

Peripherally and non-peripherally 2-diethylaminoethanethiol tetra-substituted zinc phthalocyanine (5a and 6a) and their quaternized derivatives (5b and 6b) have been synthesized and characterized. The quaternized derivatives (5b and 6b) show excellent solubility in aqueous medium. The photophysical and photochemical properties of the 2-diethylaminoethanethiol appended zinc phthalocyanine in dimethylsulfoxide (DMSO) for the non-ionic (5a and 6a) and in both DMSO and aqueous medium (phosphate buffered saline solution PBS, pH 7.4) (in the presence and absence of cremophore EL (CEL)) for the quaternized (5b and 6b) derivatives were studied and compared with that of the peripherally octa-substituted derivatives (7a and 7b). The complexes have intense absorption in the visible/near-IR region though the quaternized forms (5b, 6b and 7b) were slightly blue shifted and highly aggregate in aqueous solution. The triplet state quantum yields (_ΦT${\Phi }_{\text{T}}$) and the triplet lifetimes (_τT${\tau }_{\text{T}}$) were found to be higher in DMSO (_ΦT${\Phi }_{\text{T}}$ values ranged from 0.57 to 0.75 while _τT${\tau }_{\text{T}}$ values ranged from 190 to 220 μs in DMSO for all complexes) compared to aqueous medium (_ΦT${\Phi }_{\text{T}}$ values ranged from 0.15 to 0.17 while _τT${\tau }_{\text{T}}$ values ranged from 20 to 70 μs in pH 7.4 buffer). Addition of cremophore EL in aqueous solution resulted in induced disaggregation leading to increased _ΦT${\Phi }_{\text{T}}$ and _τT${\tau }_{\text{T}}$.     

A new oxovanadium(IV)–cucurbit[6]uril complex: Properties and potential for confined heterogeneous catalytic oxidation reactions

This work presents a new oxovanadium(IV)–cucurbit[6]uril complex, which combines the catalytic properties of the metal ion with the size-excluding properties of the macrocycle cavity. In this coordination compound, the VO²⁺${\text{VO}}^{2+}$ ions are coordinated to the oxygen atoms located at the rim of the macrocycle in slightly distorted square-pyramidal configurations, which are in fact _C2v$C_{2v}$ symmetries. This combination results in a size-selective heterogeneous catalyst, which is able to oxidize linear alkanes like n-pentane at room temperature, but not styrene, cyclohexane or z-cyclooctene, which are too big to enter the cucurbit[6]uril cavity. The results presented here contribute to understanding the mechanism of alkane catalytic oxidation by oxovanadium(IV) complexes.