Some ion exchange properties of amorphous titanium (IV) phosphate

An amorphous titanium (IV) phosphate exchanger has been synthesised and characterized through elemental analysis, infrared, and thermogravimetric techniques. Divalent cations Mn, Co, Ni, Cu, Zn, Cd, Hg and Pb in bidistilled water have been exchanged with the proton of the exchanger matrix using a batch method. From these results the thermodynamic selectivity constants and distribution coefficients were calculated, whose values indicate a high selectivity for Pb and Hg. Both cations were successfully separated from a mixture containing all cations studied through column separation experiments.     

A solid-contact Pb2+-selective polymeric membrane electrode with Nafion-doped poly(pyrrole) as ion-to-electron transducer

Conducting polymer poly(pyrrole) (PPy) doped with Nafion was successfully used as ion-to-electron transducer in the construction of a solid-contact Pb²⁺-selective polymeric membrane electrode. The Nafion dopant can effectively increase the capacitance of the conducting polymer and improve the mechanical robustness of the coating. The transducer layer, PPy-Nafion, characterized by cyclic voltammetry and electrochemical impedance spectroscopy, exhibits a sufficiently high bulk (redox) capacitance and fast ion and electron transport process. The new Pb²⁺-selective polymeric membrane electrode, based on PPy-Nafion film as solid contact, shows stable Nernstian characteristics in Pb(NO₃)₂ solution within the concentration range of 1.0 × 10⁻⁷–1.0 × 10⁻³ M, and the detection limit is 4.3 × 10⁻⁸ M. The potential stability of the electrode and the influence of the interfacial water layer were also evaluated by chronopotentiometry and potentiometric water layer test, respectively. The results show that the solid-contact Pb²⁺-selective electrode, based on PPy-Nafion film as ion-to-electron transducer, can effectively overcome the potential drift and reduce the water layer between the PPy-Nafion transducer layer and the ion-selective membrane.     

Synthesis,characterization and adsorption behaviour of TX-100 based Sn(IV) phosphate,a new hybrid ion exchanger

A new hybrid ion exchanger, Triton X-100 based tin(IV) phosphate (TX-100SnP) has been synthesized and characterized by ion exchange and physico-chemical methods such as ion exchange capacity, elution and concentration behaviour, IR, X-ray, TG/DTA and elemental analysis. Its adsorption behaviour has also been studied for some alkaline earths and heavy metal ions in different acidic media. It has been found generally more selective for metal ions as compared to tin(IV) phosphate prepared earlier. For Pb(II), Hg(II) and Fe(III) its selectivity has been found to be exceptionally good. On this basis, some binary separations have been performed involving these metal ions. Thermal studies show a high thermal stability of the material. It retains 54.54% of its i.e.c. at 200°C and 27.27% at 300°C.     

Zirconium(IV) phosphosulphosalicylate-based ion selective membrane electrode for potentiometric determination of Pb(II) ions

Zirconium(IV) phosphosulphosalicylate, a cation exchanger was synthesized by mixing zirconium oxychloride to a mixture of 5-sulphosalicylic acid and phosphoric acid. The material showed good efficiency for the preparation of an ion-selective membrane electrode. The membrane was characterized affinity for Pb(II) ions. Due to its Pb(II) selective nature, the ion-exchanger was used as an electroactive by XRD and SEM analysis. The electrode responds to Pb(II) ions in a linear range from 1 × 10⁻⁵ to 1 × 10⁻¹ M with a slope of 43.8 mV per decade change in concentration with detection limit of 4.78 × 10⁻⁶ M. The life span of electrode was found to be 90 days. The proposed electrode showed satisfactory performance over a pH range of 4.0–6.5, with a fast response time of 15 s. The sensor has been applied to the determination of Pb(II) ions in water samples of different origins. It has also been used as indicator electrode in potentiometric titration of Pb(II) ion with EDTA.     

Synthesis and ion exchange behaviour of polyaniline Sn(IV) arsenophosphate: a polymeric inorganic ion exchanger

Incorporation of a polymer material into an inorganic ion exchanger provides a class of hybrid ion exchangers with a good ion exchange capacity, high stability, reproducibility and selectivity for heavy metals. Such a type of ion exchanger ‘polyaniline Sn(IV) arsenophosphate’ has been synthesized by mixing polyaniline into inorganic material. This material is characterized using X-ray, IR, TGA studies in addition to ion exchange capacity, pH-titration, elution and distribution behaviour. On the basis of distribution studies, the material has been found to be highly selective for Pb(II). Kinetic study of exchange for the metal ions has been performed and some physical parameters such as self diffusion coefficient D₀, energy E_a and entropy ΔS* of activation have been determined.     

Comparative studies of neodymium (III)-selective PVC membrane sensors

Sensors based on two neutral ionophores, N,N′-bis((1H-pyrrol-2-yl)methylene)cyclohexane-1,2-diamine (L₁) and 3,3′-(cyclohexane-1,2-diylbis(azan-1-yl-1-ylidene)bis(methan-1-yl-1-ylidene)bis(5-hydroxymethyl)pyridine-2-ol) (L₂) are described for quantification of neodymium (III). Effect of various plasticizers; 2-nitrophenyloctylether (o-NPOE), dibutyl butylphosphonate (DBBP), tri-n-butyl phosphates (TBP), dioctylpthalate (DOP) and chloronapthalen (CN) and anion excluder, sodiumtetraphenylborate (NaTPB) has been studied. The membrane composition of PVC:o-NPOE:ionophore (L₁):NaTPB (w/w; mg) of 150:300:5:5 exhibited best performance. The sensor with ionophore (L₁) exhibits significantly enhanced selectivity towards neodymium (III) in the concentration range 5.0 × 10⁻⁷ to 1.0 × 10⁻² M with a detection limit of 1.0 × 10⁻⁷ M and a Nernstian compliance (19.8 ± 0.3 mV decade⁻¹ of activity) within pH range 4.0-8.0. The response time of sensor was found as 10 s. The influence of the membrane composition and possible interfering ions has also been investigated on the response properties of the electrode. The fast and stable response, good reproducibility and long-term stability of the sensor are observed. The sensor has been found to work satisfactorily in partially non-aqueous media up to 20% (v/v) content of methanol, ethanol or acetonitrile and could be used for a period of 3 months. The selectivity coefficients determined by using fixed interference method (FIM) indicate high selectivity for neodymium. The proposed electrode shows fairly good discrimination of neodymium (III) from other cations. The application of prepared sensor has been demonstrated in the determination of neodymium (III) in spiked water samples.     

Diffusion of Cs+ and Zn2+ through Nafion-117 ion exchange membrane

This paper discusses the diffusion of Cs⁺ and Zn²⁺ ions through Nafion-117 cation exchange membrane using radiotracer technique. The validity of the Donnan's equation is checked for these ions using⁶⁵Zn and¹³⁷Cs radiotracers. The paper also discusses the diffusion of Cl^– and I^– anions studied by using³⁶Cl and¹³¹I radiotracers. The probable mechanism of diffusion of these anions in the presence of Zn²⁺ cations is suggested.     

Synthesis,characterization, reactivity,and electrochemical studies of manganese(IV) complexes of bis(2-hydroxy-1-naphthaldehyde)adipoyldihydrazone

Manganese(IV) complexes [Mn^IV(npah)(H₂O)₂] (1) and [Mn^IV(npah)(A)₂]?·?nH₂O (where A?=?py (2), 2-pic (3), 3-pic (4), 4-pic (5)) and Mn^IV(npah)(NN)] (NN?=?bpy (6) and phen (7)) have been synthesized from bis(2-hydroxy-1-naphthaldehyde)adipoyldihydrazone in methanol. The composition of the complexes has been established by elemental analyses. Complex 3 has been characterized by mass spectral data also. Structural assessment of the complexes has been based on data from molar conductance, magnetic moment, electronic, electron paramagnetic resonance, and infrared (IR) spectral studies. Molar conductances of the complexes in DMSO suggest non-electrolytes. Magnetic moment and EPR studies suggest +4 oxidation state for manganese in these complexes. Electronic spectral studies suggest six-coordinate octahedral geometry around the metal ions. IR spectra reveal that H₄npah coordinates to the metal in enol form. Reaction of the complexes with benzyl alcohol and SO₂ has been investigated. Cyclic voltammetric studies of the complexes have also been carried out.     

Organotin(IV) complexes derived from N-ethyl-N-phenyldithiocarbamate: Synthesis,characterization and thermal studies

Organotin(IV) dithiocarbamate complexes, RSnClL₂ and R₂SnL₂ (R = Me, Bu, Ph, and L = N-ethyl-N-phenyldithiocarbamate), have been synthesized by the reaction of mono- and disubstituted organotin(IV) with ammonium dithiocarbamate. The complexes were characterized by elemental analyses, and spectroscopic techniques (¹H, ¹³C NMR and FTIR). The structures of Me₂SnL₂ and Bu₂SnL₂ were further established by single crystal X-ray diffraction technique. The crystal structure analysis showed that both complexes (Me₂SnL₂ and Bu₂SnL₂) exist as monomers. One of the dithiocarbamate ligands formed a chelate, while the other dithiocarbamate bonded to the central tin atom through one of the sulfur atoms and the second sulfur atom existed as a pendant to form distorted trigonal bipyramidal geometry. The thermal stability of all the complexes was studied using simultaneous thermogravimetry (TG) and differential scanning calorimetry (DSC). The TG-DSC results showed that Me₂SnL₂, BuSnClL₂, Bu₂SnL₂, and PhSnClL₂ displayed similar decomposition pathway via isothiocyanate intermediate, while MeSnClL₂ and Ph₂SnL₂ showed decomposition pathways different from the rest of the complexes. All the complexes resulted in SnS as the final product of the thermal decomposition process.     

Comparative studies on Tb (III)-selective PVC membrane sensors

A new terbium selective sensor based on N-(2-hydroxyphenyl)-3-(2-hydroxyphenylhydroxyphenylimino)-N-phenylbutanamidine (L₁) and N,N′-bis((1H-indole-3-yl)methylene)butane-1,4 diamine (L₂) as a ionophore is reported. Effect of various plasticizers; 2-nitrophenyloctylether (o-NPOE), dibutyl butylphosphonate (DBBP), chloronaphthelene (CN), dioctylphthalate (DOP) and tri-(2-ethylhexyl)phosphate (TEHP) with anion excluder, potassium tetrakis (p-chloropheny1)borate (KTpClPB) have been studied. The membrane with a composition of ionophore (L₁):KTpClPB:PVC:o-NPOE (w/w, %) in ratio of 3.0:5.0:30.0:62.0 exhibited enhanced selectivity towards terbium ions (III) in the concentration range of 3.5 × 10⁻⁷ to 1.0 × 10⁻² M with a detection limit of 1.2 × 10⁻⁷ M and a Nernstian slope (20.0 ± 0.5 mV dec⁻¹ activity). The sensors showed the working pH range to be 3.5-7.5 with response time of 11 s. The sensor has been found to work satisfactorily in partially non-aqueous media up to 15% (v/v) content of methanol, ethanol or acetonitrile and could be used for a period of 3 months. The selectivity coefficients indicated high selectivity for terbium (III). The fast and stable response, good reproducibility and long-term stability of the sensors were observed. The application of the sensor has been demonstrated in determination of terbium (III) ions in spiked water samples.     

Synthesis,characterization, and insulin-enhancing studies of unsymmetrical tetradentate Schiff-base complexes of oxovanadium(IV)

A series of unsymmetrical tetradentate Schiff bases were synthesized by interaction of 2-hydroxy-1-naphthaldehyde, phenylenediamine and salicylaldehyde, or substituted salicylaldehyde in an ethanolic medium. The oxovanadium(IV) complexes and the ligands were synthesized and characterized by elemental analyses, ¹H NMR, infrared, electron paramagnetic resonance, electronic spectra, cyclic voltammetry, and room temperature magnetic susceptibility measurements. The elemental analyses for both the ligands and the metal complexes confirmed purity of the compounds as formulated. Electron paramagnetic resonance spectra of the complexes were measured as powder and in toluene/dichloromethane (9 : 1, v/v) solution at room and liquid N₂ temperatures. The g values, g _o = 1.971, g _⊥ = 1.978, and g = 1.950, are the same for all the complexes examined. The vanadium nuclear hyperfine splitting, A _o = 101–99, A _⊥ = 65–64, A _∥ = 179–177, vary slightly with substituents on the salicylaldehyde. Infrared spectra reveal strong V=O stretching bands in the range 970–988 cm^?1, typical of monomeric five-coordinate complexes. The room temperature magnetic moments of 1.6–1.8 BM for the complexes confirmed that the complexes are V(IV) complexes, with d¹ configuration. Only one quasi-reversible wave is observed for each compound and they all showed redox couples with peak-to-peak separation values (ΔE _p) ranging from 78 to 83 mV, indicating a single step one electron transfer process. Insulin-mimetic tests on C2C12 muscle cells using Biovision glucose assay showed that all the complexes significantly stimulated cell glucose utilization with negligible cytotoxicity at 0.05 µg µL^?1.     

Electrical conductivity and cation exchange kinetic studies on poly-o-toluidine Th(IV) phosphate nano-composite cation exchange material

An advanced organic–inorganic cation exchange material poly-o-toluidine Th(IV) phosphate nano-composite was synthesized by a modified sol–gel technique by incorporating Th(IV) phosphate precipitate with the matrix of poly-o-toluidine. The material showed good ion-exchange behavior and used successfully in separation of metal ions. The conductivity of the composite was found within the range of 10⁻² to 10⁻³ S/cm; measured by 4-in-line-probe dc electrical conductivity measuring technique. The conductivity is at the border of metallic and semiconductor region. Ion-exchange kinetics for few divalent metal ions was evaluated by particle diffusion-controlled ion-exchange phenomenon at four different temperatures. The particle diffusion mechanism is confirmed by the linear τ (dimensionless time parameter) versus t (time) plots. The exchange processes thus controlled by the diffusion within the exchanger particle for the systems studies herein. Some physical parameters like self-diffusion coefficient (D₀)_, energy of activation (E_a) and entropy of activation (ΔS⁰) have been evaluated under conditions favoring a particle diffusion-controlled mechanism.     

Synthesis,composition and ion exchange properties of Sn(IV) and Cr(III) arsenophosphates: separation of metal ions

This paper deals with the synthesis of the arsenophosphates of various metals. The chemical composition, ion exchange capacity, thermal stability, concentration curves, elution curves, pH-titrations and IR studies have been performed on two materials, namely, Sn(IV) arsenophosphate and Cr(III) arsenophosphate. Their utility has been established by achieving four binary separations of industrial importance such as CuNi, FeCu, FeNi and CoNi on columns.     

Synthesis, spectroscopic, electrochemical and Pb2+-binding studies of tetrathiafulvalene acetylene derivatives

A series of tetrathiafulvalene acetylene derivatives, [TTF-Ctriple bondC-A] [A=C6H4N(CH3)2-4 (1), C6H4OCH3-4 (2), C6H5 (3), C6H4F-4 (4), C6H4NO2-4 (5), C5H4N-2 (6), C5H4N-3 (7), and C5H4N-4 (8)], have been designed and synthesized to provide insight into the nature of the donor-acceptor interaction via a pi-conjugated triple bond. The X-ray crystal structure of [TTF-(Ctriple bondC)-C6H4OCH3-4] (2) reveals that the phenyl ring linked by acetylene is almost coplanar to the plane of TTF with a dihedral angle of 3.6 degrees. The strong intermolecular C-H...O hydrogen bonding was found to direct the molecular helical assemblies with a screw pitch of 5.148 A when viewed along the a-axis. Spectroscopic and electrochemical behaviors of the tetrathiafulvalene acetylene derivatives demonstrate that the TTF unit interacts with the electron-accepting group through the triple bond, thus leading to the intramolecular charge transfer. The pyridine-substituted TTF compounds 6-8 show remarkable sensing and coordinating properties toward Pb2+. Comparison of the spectroscopic and electrochemical properties and the calculation at the B3LYP/6-31G* level available in Gaussian 03 reveals that varying the bridged unit of the TTF-pi-A system from a double bond to a triple bond leads to positive shifts for the first and second oxidation potentials of the TTF moieties, while the extent of intramolecular charge transfer interactions through the pi-conjugated triple bond is smaller than that through the double bond.     

Synthesis,characterization and binding studies of novel diorganotin(IV) complexes of sodium 2‐mercaptoethanesulfonate

Diorganotin(IV) complexes ( 1‐4) of MESNA (sodium 2‐mercaptoethanesulfonate HSCH₂CH₂SO₃Na) and a mixed ligand complex of dibutyltin(IV), 1,10‐phenanthroline and MESNA ( 5 ) were synthesized with thermal and microwave assisted methods. All the complexes were characterized thoroughly with the help of analytical and various spectroscopic techniques viz. FTIR, NMR (¹H, ¹³C, and ¹¹⁹Sn NMR) spectroscopy and ESI‐MS spectrometery. Various spectrophotometric studies were carried out to decipher the binding mode of MESNA and its diorganotin complexes 1 ‐ 5 with calf thymus DNA (CT DNA) and thus, to calculate the binding constant (K_b). Absorption spectrophotometric study confirmed the interaction is through partial intercalation of all the complexes including MESNA, inside the DNA helix and calculated binding constant (K_b) is in the order of 10³ M^‐1. A series of emission spectrophotometric experiments support the results obtained through the absorption spectrophotometric studies. Circular dichroic (CD) spectroscopic analysis and viscosity measurement of CT DNA further complemented the fact that the partial intercalation plays a major role in the interaction of the studied complexes with CT DNA. All the studies corroborated that complex 2 bound to CT DNA with maximum affinity followed by complex 5 among all the complexes. Involvement of hydroxyl radicals as an active species in the cleavage activity of pBR322 plasmid DNA is proved by carrying out agarose gel electrophoretic technique.     

Cation exchange and sorption properties of crystalline alpha-titanium(IV) phosphate

The ion-exchange and sorption properties of alpha-titanium bis(monohydrogen orthophosphate) monohydrate of composition Ti(HPO(4))(2).H(2)O was studied in aqueous electrolyte solutions of KCl over the temperature range of 300-320 K, varying the pH and metal ion concentration in the solution. The data were explained on the basis of the law of chemical equilibrium and the metal ion sorption data were fitted to Langmuir parameters. Further, the extent of sorption was found to increase with increasing temperature and metal ion concentration in the selectivity order Fe(3+)>Cu(2+)>Co(2+)>Mn(2+)>Cr(3+)>Ni(2+). The values of Langmuir constants were used to calculate the various thermodynamic parameters, such as DeltaG(0), DeltaH(0), and DeltaS(0), during the sorption process.     

Synthesis,characterization, and antibacterial activity of triorganotin(IV) complexes of 2-methylphenol

The triorganotin(IV) complex Ph₃Sn(OPhMe-2) (1) has been synthesized by the reaction of Ph₃SnCl with NaOPhMe-2, while complexes of composition n-Bu₃Sn(OPhMe-2) (2) and Me₃Sn(OPhMe-2) (3) (where ?OPhMe-2 = ?OC₆H₄CH₃-2) have been obtained from the reaction of n-Bu₃SnCl and Me₃SnCl with 2-methylphenol in the presence of triethylamine in carbon tetrachloride. The complexes have been characterized by elemental analyses, molar conductance measurements, molecular weight determination, and IR, ¹H NMR, ¹³C NMR, and mass spectral studies. Thermal behavior of the complexes has been studied by TG and DTA techniques. The organotin(IV) complexes have also been screened for antibacterial activity and exhibit appreciable activity. The reactions of the complexes with 3- and 4-cyanopyridines yielded 1 : 1 adducts authenticated by physicochemical and IR and ¹H NMR spectral data.