Design of Schiff base complexes of Co(II) for the preparation of iodide-selective polymeric membrane electrodes

The response characteristics of some iodide-selective solvent polymeric membrane electrodes based on with N,N'-bis(salicylaldehyde-n-octyl) diimine cobalt(II) (Co(II)SAODI) which is a more lipophilic substitute for a previously reported iodide-carrier are described. The electrode doped with Co(II)SAODI into a plasticized poly(vinyl chloride) membrane exhibits an anti-Hofmeister selectivity pattern with high selectivity toward iodide, long lifetime and small interference from H(+). Quartz crystal microgravimetric measurements and ac impedance experiments show that the excellent selectivity for iodide is related to the unique interaction between the carriers and iodide and steric effect associated with the structure of the Schiff base ligands.     

The potentiometric behavior of polymer-supported metallophthalocyanines used as anion-selective electrodes

Liquid polymer membrane electrodes based on nickel and manganese phthalocyanines were examined for use as anion-selective electrodes. The electrodes were prepared by incorporating the ionophores into plasticized poly(vinyl chloride) membranes, which were directly coated onto the surfaces of graphite electrodes. The resulting electrodes demonstrate near-Nernstian responses over a wide linear range of perchlorate anion (5 × 10⁻⁷ to 1 × 10⁻¹ M). The electrodes have a fast response time, submicromolar detection limits (5 × 10⁻⁷ M perchlorate), and could be used over a wide pH range of 3.5–10. The influences of lipophilic cationic and anionic additives on the response properties of the electrodes were investigated. The proposed sensors revealed high selectivity for perchlorate over a number of common inorganic and organic anions. The highest selectivity was observed for the electrode based on manganese phthalocyanine in the presence of the lipophilic anionic additive sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate. Application of the electrodes to determine perchlorate in tap water and human urine is also reported.      

Synthesis, transport and ionophore properties of α,ω-diphosphorylated aza podands: III. Liquid ion-selective electrodes based on phosphorylated aza podands

Aza podands having side α-aminomethylphosphine oxide groups were prepared and used as electrode-active agents in liquid membrane ion-selective electrodes. A series of liqiud membrane electrodes sensitive to Cu²⁺ and Hg²⁺ cations were prepared on the basis of N,N-bis[di(n-hexyl)phosphorylmethyl]piperazine. The electrodes containing copper complexes with aza podands as ionophores exhibit anionic function toward lipophilic anions. Potentiometric and argentometric determination of iodide ions was performed with an iodide-selective electrode based on the mercury complex.     

有机锡化合物结构与电极性能的构效关系研究

系统研究了三类有机锡化合物的阴离子响应行为。结果表明,有机锡化合物的结构与电极响应行为之间呈现出非常密切的构效关系。三类有机锡化合物对水杨酸根离子均呈现出选择性的电位响应性能,其中四配位有机锡化合物对水杨酸根离子呈现近nernst响应,而五、六配位有机锡化合物对水杨酸根离子均呈现超nernst响应。更重要的是,载体中心原子上正电荷密度对电极响应性能有很大影响。随着与锡原子相连的有机基团性质的变化,载体对水杨酸根离子的电位响应性能和选择性均发生规律性的变化,通过hammett常数定性地描述了载体结构与电极性能的构效关系。同时,通过交流阻抗、膜红外光谱等技术对电极响应机制作了初步探讨,并对超nernst现象和六配位有机锡化合物的响应行为进行了解释。     

Application of a Zeolite-Poly(vinyl chloride) Electrode to Potentiometric Studies of Alkali Metal Ions

Potentiometric electrodes based on the incorporation of zeolite particles into poly(vinyl chloride) (PVC) membranes are described. The electrode characteristics are evaluated regarding the response towards alkali ions. PVC membranes plasticized with dibutyl phthalate and without lipophilic additives (co-exchanger) are used throughout this study. The electrode exhibits a Nernstian response over the alkali metal cation concentration range of 1.0 × 10^?4 to 1.0 × 10^?1 M with a slope of 57.0 ± 0.9 mV per decade of concentration with a working pH range 3.0–9.0 and a fast response time of ≤15 s. The selectivity coefficients for cesium ion as test species with respect to alkaline earth, ammonium, and some heavy metal ions are determined. The proposed zeolite-PVC electrode is applied to the determination of ionic surfactant.     

Transition metal based supramolecular systems: synthesis, photophysics, photochemistry and their potential applications as luminescent anion chemosensors

This review describes our recent research results on several transition-metal based supramolecular systems. A number of self-assembly metallocyclophanes and cages have been prepared. We have found that the photophysical properties of these systems are highly dependent on the nature of the bridging ligands and that many of these metallocyclophanes and cages are capable of binding different guest molecules such as inorganic anions and a variety of aromatic compounds. Moreover, trinuclear (diimine) rhenium(I) tricarbonyl complexes linked by a stilbene-like ligand exhibit most interesting photoswitching features, where the luminescence from the complexes can be switched on and off by photoinduced ligand isomerization. In addition, a structurally simple and easily synthesized luminescent anion receptor has been recently developed and it displays outstanding sensitivity and selectivity toward anionic species. We also review the synthesis of two shape-persistent hexagonal phenylacetylenes and their use as ligands to synthesize dinuclear transition-metal complexes. The photophysical properties of both phenylacetylenic ligands and their corresponding metal complexes are summarized.     

Coordination properties of ionic liquid-mediated chromium(II) and copper(II) chlorides and their complexes with glucose

The structural and coordination properties of complexes formed upon the interaction of copper(II) and chromium(II) chlorides with dialkylimidazolium chloride (RMIm(+)Cl(-)) ionic liquids and glucose are studied by a combination of density functional theory (DFT) calculations and X-ray absorption spectroscopy (XAS). In the absence of the carbohydrate substrate, isolated mononuclear four-coordinated MeCl(4)(2-) species (Me = Cu, Cr) dominate in the ionic liquid solution. The organic part of the ionic liquid does not directly interact with the metal centers. The interactions between the RMIm(+) cations and the anionic metal chloride complexes are limited to hydrogen bonding with the basic Cl(-) ligands and the overall electrostatic stabilization of the anionic metal complexes. Exchange of Cl(-) ligands by a hydroxyl group of glucose is only favorable for CrCl(4)(2-). For Cu(2+) complexes, the formation of hydrogen bonded complexes between CuCl(4)(2-) and glucose is preferred. No preference for the coordination of metal chloride species to specific hydroxyl group of the carbohydrate is found. The formation of binuclear metal chloride complexes is also considered. The reactivity and selectivity patterns of the Lewis acid catalyzed reactions of glucose are discussed in the framework of the obtained results.     

Polymeric membrane electrodes with improved fluoride selectivity and lifetime based on Zr(IV)- and Al(III)-tetraphenylporphyrin derivatives

Novel aluminum(III)- and zirconium(IV)-tetraphenylporhyrin (TPP) derivatives are examined as fluoride-selective ionophores for preparing polymer membrane-based ion-selective electrodes (ISEs). The influence of t-butyl- or dichloro-phenyl ring substituents as well as the nature of the metal ion center (Al(III) versus Zr(IV)) on the anion complexation constants of TPP derivative ionophores are reported. The anion binding stability constants of the ionophores are characterized by the so-called “sandwich membrane” method. All of the metalloporphyrins examined form their strongest anion complexes with fluoride. The influence of plasticizer as well as the type of lipophilic ionic site additive and their amounts in the sensing membrane are discussed. It is shown that membrane electrodes formulated with the metalloporphyrin derivatives and appropriate anionic or cationic additives exhibit enhanced potentiometric response toward fluoride over all other anions tested. Since selectivity toward fluoride is enhanced in the presence of both anionic and cationic additives, the metalloporphyrins can function as either charged or neutral carriers within the organic membrane phase. In contrast to previously reported fluoride-selective polymeric membrane electrodes based on metalloporphyrins, nernstian or near-nernstian (−51.2 to −60.1 mV decade⁻¹) as well as rapid (t < 80 s) and fully reversible potentiometric fluoride responses are observed. Moreover, use of aluminum(III)-t-butyltetraphenylporphyrin as the ionophore provides fluoride sensors with prolonged (7 months) functional lifetime.     

Mimicking a Receptor for Cyanide Ion Based on Ion Imprinting and Its Applications in Potential Transduction

Using the strategy of template polymerization, a presynthesized specific metal‐complexing polymer (poly(methacryloylhistidine‐Ni(II)‐CN^?), Ni‐CN/IP) has been specifically used to recognize cyanide ion. As described previously, nickel(II)‐methacryloylhistidine dihydrate complex monomer was synthesized and reacted with KCN to produce the monomer‐template complex. This monomer‐template complex phase was polymerized in a dispersion medium. After polymerization, the template (CN^?) was removed from the Ni‐CN/IP, producing CN^? ion imprinted metal‐chelate polymer. The synthesized ion imprinted polymer is examined as a novel potential cyanide selective ionophore in polymeric membrane type ion selective electrodes. Membranes formulated with Ni‐CN/IP are shown to exhibit enhanced potentiometric selectivity for cyanide over more lipophilic anions including perchlorate, iodide, and thiocyanate. Addition of lipophilic cationic sites into the organic membranes enhanced the response and selectivity towards CN^? ion, while addition of lipophilic anionic sites deteriorated the response but enhanced the selectivity, indicating that the Ni‐CN/IP particles behaves via the so‐called “mixed‐mode” response mechanism. The fabricated sensors possessed good performance characteristics, in terms of life span, selectivity for CN^? ion over a wide range of other interfering anions, fast response, stability and high reproducibility. Applications for direct determination of cyanide ion in hazardous wastes using the proposed sensors showed good correlation with data obtained using commercial solid state cyanide electrode, with no significant difference in the t‐test values with 95 % confidence level. An F‐test revealed that the standard deviations of the replicate sample measurements obtained by the two methods were not significantly different.     

Photogalvanic and photovoltaic effects in systems based on metal complexes of Schiff bases

The nature of the processes that occur when electrodes modified with complexes [M(Schiff)] (M = Ni, Pd, Pt; Schiff denotes four-dentate Schiff base ligands) are irradiated with visible light for the potential use of these electrodes in photoelectrochemical energy conversion devices is considered. The factors responsible for shifts in the electrode potential upon photoexcitation, i.e., the nature of the metal site, the nature of the substituents in the sensitizer, and the oxygen concentration are discussed. Tentative mechanisms of the photovoltaic effects observed for conventional and semiconductor electrodes modified with [M(Schiff)] complexes are determined.     

二(乙基黄原酸基)金属配合物为中性载体高选择性碘离子电极的研究

本文研究了二(乙基黄原酸基)金属配合物为中性载体的阴离子选择性电极,其中二(乙基黄原酸基)钴(Ⅱ)对碘离子有高的选择性, 且电极呈现反Hofmeister行为, 其选择次序是: I^->SCN^->NO2^->Br^->ClO4^->SO4^2^->NO3^->Cl^-, 采用交流阻抗和光谱分析技术研究了电极的响应机理, 并将电极用于药品分析,结果令人满意。     

Anion-selective membrane electrodes based on metalloporphyrins: The influence of lipophilic anionic and cationic sites on potentiometric selectivity

The role of lipophilic anionic and cationic additives on the potentiometric anion selectivities of polymer membrane electrodes prepared with various metalloporphyrins as anion selective ionophores is examined. The presence of lipophilic anionic sites (e.g. tetraphenylborate derivatives) is shown to enhance the non-Hofmeister anion selectivities of membranes doped with In(III) and Sn(IV) porphyrins. In contrast, membranes containing Co(III) porphyrins require the addition of lipophilic cationic sites (e.g. tridodecylmethylammonium ions) in order to achieve optimal anion selectivity (for nitrite and thiocyanate) as well as rapid and reversible Nernstian response toward these anionic species. These experimental results coupled with appropriate theoretical models that predict the effect of lipophilic anion and cation sites on the selectivities of membranes doped with either neutral or charged carrier type ionophores may be used to determine the operative ionophore mechanism of each metalloporphyrin complex within the organic membrane phase.     

Anion selective polymeric membrane electrodes based on cyclopalladated amine complexes

The potentiometric anion selectivity of two polymer membrane based electrodes (I and II) formulated with two new cyclopalladated amine complexes as the active components are examined. The electrodes exhibit a non-Hofmeister selectivity pattern with a significantly enhanced response towards thiocyanate, iodide and nitrite. The graph potential versus log c is linear over the concentration range 10(-6)-6x10(-2) M thiocyanate with electrode I and 10(-6)-10(-3) M with electrode II; 10(-5)-10(-2) M iodide with electrode I and 10(-3)-6x10(-2) M with electrode II; and 10(-3)-6x10(-2) M nitrite with both electrodes. The influence of the plasticizer and pH are studied. The potentiometric selectivity coefficients for I, II and blank membrane electrodes are reported. The selective interaction between Pd(II) thiocyanate, iodide and nitrite is postulated to be the reason for its higher response.     

Potentiometric detection of organic acids in liquid chromatography using polymeric liquid membrane electrodes incorporating macrocyclic hexaamines

Potentiometric detection employing coated-wire electrodes was applied to the determination of organic acids in liquid chromatography (LC). Poly(vinyl chloride)-based liquid membranes, incorporating lipophilic macrocyclic hexaamines as neutral ionophores were used as electrode coatings. The selectivity and sensitivity of the macrocycle-based electrodes were found to be superior to an electrode based on a lipophilic anion exchanger (a quaternary ammonium salt). Sensitive detection was obtained for the di- and tricarboxylic acids tartaric, malonic, malic, citric, fumaric, succinic, pyruvic, 2-oxoglutaric and maleic acids after separation in reversed-phase LC. Detection limits (signal/4sigmanoise=3) of 6 pmol for malonic acid and 2 pmol for maleic acid were attained. The detection was explained using a molecular recognition model. The hexaamine-based potentiometric electrodes had a 1-s response time at 1 ml min(-1) flow-rates. They were stable for at least 4 months, with an intra-electrode variation of 3.2% (n=5).     

Membranes for chemical sensors selective to doubly charged anions

The main results concerning selective properties for carbonate, sulfate and phosphate polyvinyl chloride (PVC) membranes based on neutral carriers and anion-exchangers are discussed. It is shown that for the investigated systems selectivity depends on the concentration ratio between anion-exchanger and neutral carrier. The shape of the curves (selectivity vs. neutral carrier concentration) corresponds to a mathematical model described earlier and determines the stoichiometry of the complexes of the anions with neutral carrier. The incorporation of anionic sites inside the anion-selective membrane, e.g., carbonate-selective, leads to an increase of carbonate selectivity in presence of lipophilic anions of the internal solution.     

Schiff碱型和仲胺型双冠醚II: 用双冠醚作载体的PVC膜钾离子选择性电极

用六个含二个苯并-15-冠-5单元的席夫碱型和仲胺型新型双冠醚作载体制备了钾离子选择性PVC膜电极,并研究了它们的电极行为,这些电极对所有的其它碱金属和碱土金属离子展现出显著的钾离子选择性,可期望有一定的应用价值.     

Electropolymerization of Metallophthalocyanines Carrying Redox Active Metal Centers and their Electrochemical Pesticide Sensing Application

In this study, modified electrodes were constructed with the electropolymerization of metallophthalocyanines (MPcs) carrying redox active metal cations and electropolymerizable substituents. Then these electrodes were tested as selective and sensitive electrochemical pesticide sensors. Incorporation of the redox active Co(II) (CoPc(MOR‐NAF)), Cl–Mn(III) (MnPc(MOR‐NAF)), and Ti(IV)O (TiOPc(MOR‐NAF)) metal cations into Pc cavity increased the redox activity of Pc ring. Moreover, redox active and electropolymerizable 5‐{[(1E)‐(4‐morpholin‐4‐ylphenyl)methylene]amino}‐1‐naphthoxy substituents (MOR‐NAF) on the Pc ring triggered coating of the complexes on the electrode surface with the electropolymerization reactions. Therefore, modified electrodes GCE/MPc(MOR‐NAF) were constructed with the electropolymerizations of MPcs. These electrodes illustrated reasonable redox activity and conductivity for the potential applications in different fields of the electrochemical technologies. Pesticide sensing measurements indicated that changing the metal center of the complexes significantly altered their sensing activities. Among the complexes, GCE/CoPc(MOR‐NAF) electrode behaved as the most sensitive and selective electrode and it sensed the parathion with good selectivity and sensitivity. GCE/CoPc(MOR‐NAF) electrode showed a wider linear range (0.075‐5.75 μmoldm⁻³) and smaller LOD (0.025 μmoldm⁻³) and higher sensitivity (3.46 Acm⁻²M⁻¹) for the parathion sensing. Although GCE/TiOPc(MOR‐NAF) electrode also sensed the parathion with a high sensitivity, its selectivity was poor and the linear range of this sensing was very narrow. Differently GCE/Cl–MnPc(MOR‐NAF) electrode only sensed eserine with reasonably sensitivity.     

Poly(vinyl chloride) membrane cesium ion-selective electrodes based on lipophilic calix[6]arene tetraester derivatives

New lipophilic tetraesters of calix[6]arene and calix[6]diquinone are investigated as cesium ion-selective ionophores in poly(vinyl chloride) membrane electrodes. For an ion-selective electrode based on calix[6]arene tetraester I, the linear response is 1x10(-6)-1x10(-1) M of Cs(+) concentrations. The selectivity coefficients for cesium ion over alkali, alkaline earth and ammonium ions are determined. The detection limit (log a (Cs (+))=-6.31) and the selectivity coefficient (log k (Cs (+),Rb (+))(pot )=-1.88) are obtained for polymeric membrane electrode containing calix[6]arene tetraester I.     

Membranes for chemical sensors selective to doubly charged anions

The main results concerning selective properties for carbonate, sulfate and phosphate polyvinyl chloride (PVC) membranes based on neutral carriers and anion-exchangers are discussed. It is shown that for the investigated systems selectivity depends on the concentration ratio between anion-exchanger and neutral carrier. The shape of the curves (selectivity vs. neutral carrier concentration) corresponds to a mathematical model described earlier and determines the stoichiometry of the complexes of the anions with neutral carrier. The incorporation of anionic sites inside the anion-selective membrane, e.g., carbonate-selective, leads to an increase of carbonate selectivity in presence of lipophilic anions of the internal solution. Received: 28 July 1997 / Revised: 11 December 1997 / Accepted: 20 December 1997     

Pentacoordinate organotin complexes as neutral carriers for salicylate-selective PVC membrane electrodes

Selectivity properties are established for three new electrodes prepared by incorporating three pentacoordinate organotin(IV) complexes, mono(2,4-pentanedionato-o,o') tri(phenylmethyl)tin (DMTBS), mono(benzoylacetonato-o,o') tri(phenylmethyl)tin (MPTBS) and mono(dibenzoylmethanato-o,o') tri(phenylmethyl)tin (DPTBS) into plasticized PVC membranes. These electrodes exhibit linear response to salicylate and an anti-Hofmeister selectivity pattern with high specificity for salicylate over many common anions. The results show that the potentiometric response characteristics are related to the structure of organic ligands. The detection limit and the slope of the electrodes based on these pentacoordinate organotin complexes exhibit a tendency to decrease as the substituent in organic ligands changes from a methyl group to a phenyl group. Electrodes prepared with DMTBS have the best detection limit and the highest degree of selectivity and sensitivity for salicylate. The response mechanism is also investigated by use of a.c. impedance and i.r. spectroscopic techniques.