Out-cage metal ion coordination by novel benzoazacrown bisamides with carboxyl,pyridyl and picolinate pendant arms

A new series of macrocyclic diamides with carboxyl, pyridyl and picolinate pendant arms have been synthesized and the stability constants of their complexes with Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Pb²⁺ in water were determined. Complexes with a stoichiometry of 1 : 1 (M: L) were found for all ligands with the exception of 15-membered crown ethers with one pendant carboxyl or pyridine group. The ligand containing two picolinate backbone groups exhibits the highest values of the stability constants for all studied cations (logβ_ML?=?12.5–15.7). X-ray study of free ligands showed that the introduction of benzene and amide fragments into the macrocyclic moiety provides a flatten open structure of the ligand. The crystallographic analysis of Cu²⁺ and Zn²⁺ complexes revealed the external coordination of the metal atom by amine N atoms of the macrocycle and heteroatoms of the pendant groups.     

Comparison of Several Calibration Procedures for Glass Electrodes in Proton Concentration

Summary. Several reported procedures for calibrating glass electrodes in proton concentration are compared. Some recommendations for non-experts are also given. The examined procedures can be classified into two broad categories, namely: those based on direct potential difference measurements of solutions of known proton concentration and those that use one or several pH standards to calibrate the electrode and subsequently measure the pH of solutions containing known proton concentrations. With a single buffer, the two types of procedures lead to equivalent results. However, if two pH buffers are used, the slope of the calibration graph in proton concentration will differ from the real electrode slope to an extent proportional to the difference between the liquid junction potentials of the two buffers. Therefore, any other method is preferable under these circumstances.     

Characteristic of the Ag(II)/Ag(I) system in the presence of 2-pyridinecarboxylic acid in acetonitrile

Summary Formation constants of the complexes of Ag(I) with 2-pyridine-carboxylic acid (Hpic) were determined by the potentiometric method: ₀₁=36, ₀₂=537. It was shown by IR spectroscopy that the complexation of Ag(I) ions in acetonitrile proceeds without the formation of Ag-O bond and the complexes have the following forms: AgHpic ⁺ and Ag(Hpic) ₂ ⁺ . Oxidation of Ag(Hpic) ₂ ⁺ at the potential =1850 mV vs. NHE resulted in the complex Ag(Hpic) ₂ ²⁺ . The formal potentialE _f ⁰ =1.772 V vs. NHE of the system Ag(Hpic) ₂ ²⁺ +eAg(Hpic)⁺+Hpic was determined by chronovoltamperometry, while the formal potentialE _f ⁰ =1.841 V vs. NHE of the system Ag(Hpic) ₂ ²⁺ +eAg(Hpic) ₂ ⁺ was calculated. Properties of the system in water and acetonitrile were compared.

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Charakteristik des Ag(II)/Ag(I)-Systems in Gegenwart von 2-Pyridincarbonsäure in Acetonitril

Zusammenfassung Es wurden die Bildungskonstanten der Komplexe von Ag(I) mit 2-Pyridincarbonsäure (Hpic) mittels Potentiometrie bestimmt: ₀₁=36, ₀₂=537. Die IR-Spektren bewiesen, daß die Komplexierung von Ag(I)-Ionen über die Ausbildung einer Ag-O-Bindung verläuft, wobei die Komplexe die folgenden Formeln besitzen: AgHpic ⁺ und Ag(Hpic) ₂ ⁺ . Die Oxidation von Ag(Hpic) ₂ ⁺ beim Potential =1850 mV gegenüber NHE ergab den Komplex Ag(Hpic) ₂ ²⁺ . Das formale PotentialE _f ⁰ =1.772 V (gegenüber NHE) des Systems Ag(Hpic) ₂ ²⁺ +eAg(Hpic)⁺+Hpic wurde mittels Chronovoltamperometrie ermittelt, während das formale PotentialE _f ⁰ =1.841 V (gegenüber NHE) des Systems Ag(Hpic) ₂ ²⁺ +eAg(Hpic) ₂ ⁺ berechnet wurde. Außerdem wurden die Eigenschaften der Systeme in Wasser und Acetonitril verglichen.

     

[Cu(L)](NO3)2 (L=4,7‐Bis(3‐aminopropyl)‐1‐thia‐4,7‐diazacyclononane) as a Suitable Ionophore for Construction of Thiocyanate‐Selective Electrodes and Their Use in Determination of Urinary and Salivary Thiocyanate Concentration

The construction, performance characteristics, and application of polymeric membrane (PME) and coated graphite (CGE) thiocyanate‐selective electrodes are reported. The electrodes were prepared by incorporating the complex [Cu(L)](NO₃)₂ (L=4,7‐bis(3‐aminopropyl)‐1‐thia‐4,7‐diazacyclononane) into a plasiticized poly(vinyl chloride) membrane. The influence of membrane composition, pH of test solution, and foreign ions were investigated. The electrodes reveal Nernstian behavior over a wide SCN^? ion concentration range (1.0×10^?6–1.0×10^?1 M for PME and 5.0×10^?7–1.0×10^?2 M for CGE) and show fast dynamic response times of 15 s and lower. The proposed sensors show high selectivity towards thiocyanate over several common organic and inorganic anions. They were successfully applied to the direct determination of thiocyanate in urine and saliva of smokers and nonsmokers, and as an indicator electrode in titration of Ag⁺ ions with thiocyanate.     

Novel Liquid Membrane Electrode for Selective Determination of Monohydrogenphosphate

A highly selective and sensitive membrane electrode based on vanadyl salen complex (VS), which responds to monohydrogenphosphate (MHP) ions is described. The response of the sensor is Nernstian over the wide concentration range (1.0×10^?1 ? 5.0×10^?6 M) of MHP. The sensitivity of the electrode is high enough to permit the detection of as little as 0.6 μg/mL of MHP without any significant interference from high levels of other anions. The potentiometric selectivity coefficient data revealed negligible interference from 11 common anions. The electrode has a fast response time (<25 s), good slope stability at pH 8.2 for a period of at least eight weeks. It was successfully applied for the direct determination of monohydrogenphosphate in fertilizer and, as indicator electrode, in potentiometric titration of HPO₄^2? ion with barium chloride.     

Chelation behaviour of lanthanides with somethio-Schiff bases

Summary The stability constants of complexes of trivalent Y, La, Ce, Pr, Sm, Gd, Dy, Ho, Er, and Yb ions with somethio-Schiff bases have been determined potentiometrically using theCalvin-Bjerrum titration technique as modified byIrving andRossotti at 25 °C and an ionic strength of 0.1M (NaCl) in 70% (v/v) aqueous ethanol. 1:1 and 1:2 complexes are formed and evidenced by conductometric studies. ThepK _a values of the SH group were correlated with theHammet constants of substituents. The values of the stability constants are correlated with the atomic numbers of the lanthanides and with the sum of the ionization constants of the ligands.

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Komplexierungsverhalten von Lanthaniden mit einigenthio-Schiff schen Basen

Zusammenfassung Die Stabilitätskonstanten von Komplexen trivalenter Y-, La-, Ce-, Pr-, Sm-, Gd-, Dy-, Ho-, Er- und Yb-Ionen mit einigenthio-Schiffschen Basen wurden potentiometrisch unter Verwendung der vonIrving undRossotti modifiziertenCalvin-Bjerrum-Titrationstechnik bei 25 °C undI=0.1M (NaCl) in 70% (v/v) wäßrigem Ethanol bestimmt. Wie konduktometrisch gezeigt werden konnte, treten 1:1- und 1:2-Komplexe auf. DiepK _a -Werte der SH-Gruppen wurden mit denHammetschen Substituentenkonstanten korreliert, die Stabilitätskonstanten mit den Kernladungszahlen der Lanthaniden und mit der Summe der Ionisationskonstanten der Liganden.

     

Highly selective and sensitive monohydrogen phosphate membrane sensor based on molybdenum acetylacetonate

In this work, a highly selective and sensitive monohydrogen phosphate membrane sensor based on a molybdenum bis(2-hydroxyanil) acetylacetonate complex (MAA) is reported. The sensor shows a linear dynamic range between 1.0 × 10⁻¹ and 1.0 × 10⁻⁷ M, with a nice Nernstian behavior (−29.5 ± 0.3 mV decade⁻¹) in pH of 8.2. The detection limit of the electrode is 6.0 × 10⁻⁸ M (∼6 ppb). The best performance was obtained with a membrane composition of 32% poly(vinyl chloride), 58% benzyl acetate, 2% hexadecyltrimethylammonium bromide and 8% MAA. The sensor possesses the advantages of short response time, low detection limit and especially, very good selectivity towards a large number of organic and inorganic anions including salicylate, citrate, tartarate, acetate, oxalate, fluoride, chloride, bromide, iodide, sulfite, sulfate, nitrate, nitrite, cyanide, thiocyanate, perchlorate, metavanadate, and bicarbonate ions. The electrode can be used for at least 10 weeks without any considerable divergence in its slope and detection limit. It was used as an indicator electrode in potentiometric titration of monohydrogenphosphate ion with barium chloride. The proposed sensor was successfully applied to direct determination of monohydrogenphosphate in two fertilizer samples (NPK).     

A Novel Potentiometric Membrane Sensor Based on Aryl Palladium Complex for Selective Determination of Thiocyanate in the Saliva and Urine of Cigarette Smokers

A highly selective potentiometric sensor for thiocyanate ion based on the use of a newly synthesized organo‐palladium ion exchanger complex dispersed in a plasticized poly(vinyl chloride) membrane is described. The sensor displays a Nernstian response (?57.8±0.2 mV decade^?1) over a wide linear concentration range of thiocyanate (1.0×10^?6–1.0×10^?1 mol L^?1 ), low detection limit (6.3×10^?7 mol L^?1), fast response (20 s), stable potential readings (±0.4 mV), good reproducibility (±0.9%), long term stability (8 weeks), high precision (±0.7%) and applicability over a wide pH range (4–10). Negligible interferences are caused by F^?, Cl^?, I^?, Br^?, NO₃^?, NO₂^?, CN^?, SO₄^2?, S₂O₃^2?, PO₄^3?, citrate, acetate and oxalate ions. Under hydrodynamic mode of operation (FIA), the calibration slope is ?51.1±0.1 mV decade^?1, the linear response range is 1.0×10^?5–1.0×10^?1 mol L^?1 SCN^? and the sample throughput is 40–45 per hour. The sensor is satisfactory used for manual and flow injection potentiometric determination of SCN^? in the saliva and urine of cigarette smokers and non smokers. The data agree fairly well with results obtained by the standard spectrophotometric technique. Direct potentiometry and potentiometric titration of SCN^? with Ag⁺ are also monitored with the sensor.     

Highly Selective and Sensitive Copper(II) Membrane Sensors Based on 6‐Methyl‐4‐(1‐phenylmethylidene)amino‐3‐thioxo‐1,2,4‐triazin‐5‐one as a New Neutral Ionophore

A new Cu(II) ion‐selective PVC membrane sensor based on 6‐methyl‐4‐(1‐phenylmethylidene)amino‐3‐thioxo‐1,2,4‐triazin‐5‐one (MATTO) as an excellent sensing material was developed. The electrode exhibits a Nernstian slope of 29.2±0.4 mV per decade over a very wide concentration range between 1.0×10^?1 and 1.0×10^?6 M, with a detection limit of 4.8×10^?7 M (30.5 ng/mL). The sensor possesses the advantages of short conditioning time, fast response time (<10 s), and especially, very good selectivity towards transition and heavy metal, and some mono, di and trivalent cations. The proposed electrode was successfully applied to the determination of copper in wastewater of copper electroplating samples and as an indicator electrode in potentiometric titration of Cu(II) ions with EDTA.     

Thermodynamic parameters for the binding of inorganic and organic anions by biogenic polyammonium cations

Thermodynamic parameters for the interaction of protonated biogenic polyamines with inorganic or organic polyanions were studied potentiometrically (H(+)-glass electrode) and calorimetrically, at 25 degrees C. No background salt was used in the measurements to avoid interferences, and the formation constants and formation enthalpies were extrapolated to zero ionic strength. Species formed are ALH(r) [L=Cl(-), SO(4)(2-), HPO(4)(2-), P(2)O(7)(4-) and P(3)O(10)(5-); tartrate, malate, citrate, glutamate, 1,2,3-propanetricarboxylate, 1,2,3,4-butanetetracarboxylate], with r=1,2...(n+m-2) and r=1,2...(n+m-1) for inorganic and organic ligands, respectively (n, m=maximum degree of protonation of amine and ligand, respectively). The stability of the various species formed is a function of charges involved in the formation reaction. DeltaH(0) values are generally positive, and therefore these complexes are entropically stabilized. Results are discussed in connection with several previously reported data on similar systems. DeltaG(0) and TDeltaS(0) follow a linear trend as a function of polyammonium cation and inorganic or carboxylic anion charges. DeltaG(0) and TDeltaS(0) charge relationships are reported. In particular, mean values of DeltaG(0) and TDeltaS(0) for single interaction were calculated: DeltaG(0)=7.0 kJ mol(-1) n(-1), TDeltaS(0)=9.1 kJ mol(-1) n(-1) and DeltaG(0)=5.7 kJ mol(-1) n(-1) and TDeltaS(0)=8.7 kJ mol(-1) n(-1), for the species of inorganic and organic polyanions, respectively (n=number of possible salt bridges). A linear relationship was also found for TDeltaS(0) versus DeltaG(0), whose equation is TDeltaS(0)=-7-1.39 DeltaG(0) (with r=0.9409; r, correlation coefficient). The body of correlations found for these thermodynamic parameters shows quite good predictive value.