Copper(II)-selective electrode based on dithioacetal

A PVC membrane electrode for copper ion based on 1,3-dithiane,2-(4-methoxy phenyl) as ionophore and o-nitrophenyl octyl ether as a plasticizer is demonstrated. The electrode exhibits a Nernstian slope of 29.5±1 mV per decade in a linear range of 3.0×10⁻⁶ to 5.0×10⁻² M for Cu²⁺ ion. The detection limit of this electrode is 1.0×10⁻⁶ mol/l. This sensor has a very short response time of about 5 s and could be used in a pH range of 4.0-7.0. High selectivity was obtained over a wide variety of metal ions. The proposed electrode was successfully applied as an indicator electrode for the potentiometric titration of copper ion with EDTA and for the direct determination of copper in river water.     

Zn(II)-selective membrane electrode based on tetra(2-aminophenyl) porphyrin

A new PVC membrane electrode for Zn²⁺ ions based on tetra(2-aminophenyl) porphyrin (TAPP) as membrane carrier is prepared. The sensor exhibits a linear stable response over a wide concentration range (5.0×10⁻⁵ to 1.0×10⁻¹ M) with a slope of 26.5 mV/decade and a limit of detection 3.0×10⁻⁵ M (1.96 ppm). It has a response time of about l0 s and can be used for at least 8 months without any divergence in potential. The propose membrane sensor revealed good selectivities for Zn²⁺ over a wide variety of other metal ions and can be used in pH range of 3.0–6.0. It was successfully applied to the direct determination of zinc in a pharmaceutical sample and also as an indicator electrode in potentiometric titration of Zn²⁺ ions.     

Facile synthesis of multinuclear complexes based on a tetra(4-pyridyl)amidinate dirhodium(II) dimer

Four rhenium(I) chromophores attached to a dirhodium(n) core form a new hexametallic light-harvesting assembly as characterised by X-ray crystallography, UV-vis spectroscopy and electrochemistry.     

Ca(II) and Ba(II) methyl carbazate energetic complexes: syntheses,crystal structures,and properties

New energetic materials, [Ca(MCZ)₃(H₂O)₂](ClO₄)₂ and {[Ba₂(MCZ)₄(H₂O)₂(μ₁-ClO₄)₂(μ₂-ClO₄)₂]_0.5}_n, are synthesized and tried as alternatives to common primary explosives. Both the crystal structures were determined by single-crystal X-ray diffraction. The crystal of [Ca(MCZ)₃(H₂O)₂](ClO₄)₂ belongs to the monoclinic, P2₁/c space group, a = 14.168(3) Å, b = 8.5938(18) Å, c = 18.889(4) Å, β = 111.234(2)°, V = 2143.8(8) Å³, ρ = 1.6893 g cm^?3, and {[Ba₂(MCZ)₄(H₂O)₂(μ₁-ClO₄)₂(μ₂-ClO₄)₂]_0.5}_n belongs to the triclinic, P-1 space group, a = 7.166(2) Å, b = 10.461(2) Å, c = 11.738(4) Å, α = 110.563(5)°, β = 93.799(2)°, γ = 96.864(3)°, V = 812.4(4) Å³, ρ = 2.185 g cm^?3. Their thermal stabilities were investigated by differential scanning calorimetry (DSC), and exothermic peak temperatures with a heating rate of 10 °C min^?1 are 249.7 and 181.7 °C, respectively. Non-isothermal reaction kinetics parameters were calculated via both Kissinger’s method and Ozawa-Doyle’s method to work out E_K = 124.6 kJ mol^?1, lgA_K = 10.38, E_O = 126.7 kJ mol^?1 for the calcium complex and E_K = 100.3 kJ mol^?1, lgA_K = 9.50, E_O = 102.6 kJ mol^?1 for the barium complex. Additionally, the critical temperatures of thermal explosion, ΔS^≠, ΔH^≠, and ΔG^≠ were calculated as ?231.2 J K^?1 mol^?1, 120.417 kJ mol^?1, 236.728 kJ mol^?1 for the calcium complex and ?230.6 J K^?1 mol^?1, 96.723 kJ mol^?1, 195.938 kJ mol^?1 for the barium complex. As for their explosive nature, sensitivities toward impact and friction were tested. Both [Ca(MCZ)₃(H₂O)₂](ClO₄)₂ and {[Ba₂(MCZ)₄(H₂O)₂(μ₁-ClO₄)₂(μ₂-ClO₄)₂]_0.5}_n are insensitive to friction (>360 N); their impact sensitivities are acceptable (20 and 13 J). Both compounds are energetic complexes.     

Expedient method for the transmetalation of Zn(II)-centered salphen complexes

Various mono- and bis-ZnII complexes derived from salphen ligands have been conveniently transmetalated with a number of transition metal (TM) acetates (M=Ni, Pd, Mn) in THF to afford their respective TM-salphen counterparts in excellent isolated yields (80-100%). This new transmetalation procedure allows in situ switching between supramolecular and catalytic functions of the metallosalphen complex.     

Anion-selective receptors based on dinuclear copper(II) and nickel(II) cage complexes of bis-salicylaldimines

The selectivity, anion uptake and exchangeability of anion-binding by metal salt extractants of the form [M₂ L ₂]⁴⁺ have been assessed by the method of anion exchange chromatography in biphasic systems. The order of sulfate-, nitrate-, and chloride-uptake into the solid copper(II) complex as of the dioxime pro-ligand N,N??-dimethyl-N,N??-hexamethylenedi(3-hydroxyiminomethyl-2-hydroxy-5-tert-butylbenzylamine (L ¹ ) is 56, 42, and 16%, respectively, consistent with the relative magnitudes of formation constants for the inclusion complexes, [A?Cu₂ L ¹ ₂] ⁿ⁺ where A = anion, found in UV?Cvis titration studies in a single phase. X-ray structural determination of the bis-benzylimine pro-ligand, N,N??-dimethyl-N,N??-hexamethylenedi-(3-benzyliminomehyl-2-hydroxy-5-tert-butylbenzylamine), nickel(II) sulfato complex [SO₄?Ni₂ L ² ₂]SO₄ reveals the nickel atoms to have a significant tetrahedral distortion, providing more favourable sulfate-alkylammonium interactions within the cage.     

Branched carbon-rich luminescent multinuclear platinum(II) and palladium(II) alkynyl complexes with phosphine ligands

In this review, the synthesis, electronic absorption and luminescent properties of a series of branched alkynylpalladium(II) and -platinum(II) phosphine complexes with different alkynyl backbones and some of their structurally related complexes in the literature will be discussed. With the growing research interest in the potential application of these complexes in the field of non-linear optics (NLO), the two-photon absorption (TPA) properties and the corresponding structure–property relationships of selected luminescent branched platinum(II) bis-alkynyl complexes will also be described.     

Hg2+-selective OFF-ON and Cu2+-selective ON-OFF type fluoroionophore based upon cyclam

[structure: see text]. A new cyclam derivative having two different fluorophores of pyrene and NBD subunits was prepared, and its Hg2+- and Cu2+-selective signaling behaviors were investigated. The detection limits for the analysis of Hg2+ and Cu2+ ions were found to be 7.9 x 10(-6) and 2.6 x 10(-7) M in aqueous acetonitrile solution (H2O-CH3CN = 10:90, v/v), respectively. The compound also exhibited a selective Hg2+/Cu2+-induced OFF-ON-OFF type of signaling pattern that can be utilized for the construction of functional supramolecular switching systems.     

Itinerant electron ferromagnetism in Sr2+-, Ca2+-, and Ba2+-doped rare-earth orthocobaltites (Ln3+1−xM2+xCoO3)

Electronic and magnetic properties of Ln_1?xSr_xCoO₃ (Ln = Pr, Nd, Sm, Eu, and Gd) systems show that above a critical value of x, the d electrons become itinerant while the materials become ferromagnetic at low temperatures. The ferromagnetic component increases with increase in x and decrease in temperature. The Curie temperature increases with x and decreases with decrease in the size of the rare-earth ion. Incorporation of Ba²⁺ in LaCoO₃ favors itinerant electron ferromagnetism relative to Sr²⁺ while Ca²⁺ is less favorable than Sr²⁺.     

Strontium(II)-selective electrode based on a macrocyclic tetraamide

A new PVC membrane electrode based on 5,7,12,14-dibenzo-2,3,9,10-tetraoxa-1,4,8,11-tetraazacyclotetradecane (I) as an ion carrier, o-nitrophenyloctyl ether (o-NPOE) as solvent mediator and sodium tetraphenylborate (NaTPB) as lipophilic additive was fabricated and investigated as Sr²⁺-selective electrode. The best performance was exhibited by the membrane having composition 8:200:4:120 (I:o-NPOE:NaTPB:PVC). The electrode exhibited a Nernstian response for strontium ion over a wide concentration range 3.98 × 10⁻⁶ to 1.0 × 10⁻¹ M with a slope of 29.0 ± 0.1 mV/decade of concentration and a detection limit of 2.82 × 10⁻⁶ M. It showed a response time of less than 10 s and could be used for at least 3 months without any divergence in potential. The proposed electrode showed a good discriminating ability towards strontium(II) ion over a wide variety of other metal ions including alkali, alkaline earth, transition, and heavy metal ions. The electrode can be used in the pH range of 2.5-10.5 and in mixtures containing up to 35% (v/v) non-aqueous content. It was used as an indicator electrode in potentiometric titration of strontium ion against EDTA.     

Cobalt(II), nickel(II) and copper(II) complexes of 5-(2-carboxyphenylazo)-2-thiohydantoin

A new series of hexacoordinate cobalt(II), nickel(II) and copper(II) complexes of 5-(2-carboxyphenylazo)-2-thiohydantoin HL having formulae [LM(OAc)(H₂O)₂] · nH₂O (M = Co^II, Cu^II and Ni^II), [LMCl(H₂O)₂] · nH₂O (M = Co^II and Ni^II), [LCuCl(H₂O)]₂ · 2H₂O, [LCu(H₂O)₃](ClO₄) and [LCu(HSO₄)(H₂O)₂] were isolated and characterized by elemental analyses, molar conductivities and magnetic susceptibilities, and by i.r., electronic and e.s.r. spectral measurements, as well as by thermal (t.g. and d.t.g.) analyses. The i.r. spectra indicate that the ligand HL behaves as a monobasic tridentate towards the three divalent metal ions via an azo-N, carboxylate-O and thiohydantoin-O atom. The magnetic moments and electronic spectral data suggest an octahedral geometry for Co^II complexes, distorted octahedral geometry for both Ni^II and Cu^II complexes with a dimeric structure for [LCuCl(H₂O)]₂ · 2H₂O through bridged chloro ligands. The X-band e.s.r. spectra reveal an axial symmetry for the copper(II) complexes with unsymmetrical M_s = ± 1 signal and G-parameter less than four for the dimeric [LCuCl(H₂O)]₂ · 2H₂O. The thermogravimetry (t.g. and d.t.g.) of some complexes were studied; the order and kinetic parameters of their thermal degradation were determined by applying Coats–Redfern method and discussed.     

Divalent metal complexes (Ca, Sr, Ba, Yb) of the unsymmetrical 3-(2'-thienyl)-5-(trifluoromethyl)pyrazolate ligand

The divalent complexes [M(ttfpz)(2)(thf)(4)] (ttfpz = 3-(2'-thienyl)-5-(trifluoromethyl)pyrazolate; M = Yb, 1, Ca, 2, Sr, 3, Ba, 4; thf = tetrahydrofuran) and [M(ttfpz)(2)(dme)(n)] (M = Ca, 5, Sr, 6, Yb, 7, n = 2; M = Ba, 8, n = 3; dme = 1,2-dimethoxyethane) have been prepared by redox transmetallation/protolysis reactions employing the free metals, Hg(C(6)F(5))(2) and ttfpzH in donor solvents and their structures determined. The monomeric structures exhibit η(2)-bound pyrazolate ligands with eight-coordinate metal atoms for complexes 1-7 and a ten-coordinate metal for 8. The pyrazolate ligands in the thf-complexes 1-4 as well as dme-derivatives 5 and 6 are in a transoid configuration, whilst in complex 7 the ttfpz ligands exhibit a cisoid relationship. In 8 the ligands have an intermediate role in between cisoid and transoid.     

Lead(II)-selective electrode based on phenyl disulfide.

A PVC membrane electrode for lead ions based on phenyl disulfide as the membrane carrier was developed. The electrode exhibits a good Nernstian slope of 29.3 +/- 0.7 mV/decade and a linear range of 2.0 x 10(-6)-1.0 x 10(-2) M for Pb(NO3)2. The limit of detection is 1.2 x 10(-6) M. It has a response time of 45 s and can be used for at least fifty days without any divergence in potential. The proposed membrane sensor revealed high selectivity for Pb2+ over a wide variety of other metal ions and could be used in the pH range of 3.5-6.3. The electrode was used as an indicator electrode in potentiometric titration of lead ions.     

A new family of Ru(II) polypyridyl complexes containing open-chain crown ether for Mg2+ and Ca2+ probing

Six polypyridyl bridging ligands BL(1-6) containing open-chain crown ether, where BL(1-3) formed by the condensation of 4,5-diazafluoren-9-hydrazine with 1,7-bis-(4-formylphenyl)-1,4,7-trioxaheptane, 1,10-bis-(4-formylphenyl)-1,4,7,10-tetraoxadecane, and 1,13-bis-(4-formylphenyl)-1,4,7,10,13-pentaoxatridecane, respectively, BL(4-6) formed by the reaction of 9-(4-hydroxy)phenylimino-4,5-diazafluorene with diethylene glycol di-p-tosylate, triethylene glycol di-p-tosylate, and tetraethylene glycol di-p-tosylate, respectively, have been synthesized. Reaction of Ru(bpy)(2)Cl(2).2H(2)O with BL(1-6), respectively, afforded six bimetallic complexes [(bpy)(2)RuBL(1-6)Ru(bpy)(2)](4+) as PF(6)(-) salts. Cyclic voltammetry of these complexes is consistent with one Ru(II)-centered oxidation around 1.32V and three ligand-centered reductions. These complexes show metal-to-ligand charge transfer absorption at 413-444 nm and emission at 570 nm. Binding behavior of complexes with alkali and alkaline-earth metal ions are investigated by UV-vis absorption, fluorescence, and cyclic voltammetry. Addition of alkali and alkaline-earth metal ions to the solution of [(bpy)(2)RuBL(1-6)Ru(bpy)(2)](PF(6))(4) all result in a progressive quenching of fluorescence, a hyperchromic effect of UV-vis absorption, and a progressive cathodal shift of Ru(II)-centered E(1/2). Ru-BL(2) and Ru-BL(5) show the highest binding ability toward Mg(2+) among the five cations examined while Ru-BL(3) and Ru-BL(6) exhibit good selective recognition ability to Ca(2+).     

Three multinuclear Co(II), Zn(II) and Cd(II) complexes based on a single-armed salamo-type bisoxime: syntheses,structural characterizations and fluorescent properties

Three multinuclear complexes, [Co(L)(OAc)Co(CH₃CH₂OH)₂]·H₂O, [Zn(L)(OAc)Zn(CH₃OH)], and [{Cd(L)(OAc)Cd(CH₃OH)}₂], containing a single-armed salamo-type bisoxime H₃L have been synthesized and characterized structurally. The Co(II) complex forms a dimeric unit by intermolecular hydrogen bond interactions of neighboring dimeric molecules. The Zn(II) complex also forms a dimeric unit by intermolecular hydrogen bond interactions. Interesting features of the crystal structure include O?O short contacts. Meanwhile, self-assembling infinite 1-D, 2-D, and 3-D supramolecular structures are formed by intermolecular hydrogen bond and C–H?π interactions. The Cd(II) complex forms an infinite 2-D supramolecular structure by intermolecular hydrogen bond interactions. The photophysical properties of the Co(II), Zn(II), and Cd(II) complexes have also been discussed.     

Preparation and characterization of Mg(II)-, Ca(II) and Cd(II) complexes of 1,2-ethanediol and water

Mixed ligand complexes of different compositions were prepared with water, sulfate ion and 1,2-ethanediol as ligand. IR spectra and the thermoanalytical curves of the complexes were recorded. Oxygen atoms bound by one or two coordinate bonds to the metal ion, or by hydrogen-bonds in the crystal, were observed. As for the water molecule, 1,2-ethanediol molecules of crystal and monohydrate type were found, depending on the type of binding of the oxygen atoms.This revised version was published online in November 2005 with corrections to the Cover Date.     

Assisted intramolecular proton transfer in (uracil)2Ca2+ complexes

The structure and relative stability of the complexes between uracil dimers and Ca²⁺, as well as the proton transfer (PT) processes within these dimers, have been investigated by the density functional theory methods. Although in uracil dimers PT occurs as an almost synchronous double PT processes that connect the diketo dimer with a keto-enol dimer, the process within the most stable (uracil)₂Ca²⁺ complexes is much more complicated, and the product of the reaction looks like the result of an intramolecular PT from one of the NH groups of one monomer to one of the carbonyl groups of the same monomer. An analysis of the force profile along the reaction coordinate shows that the intimate mechanism implies three elementary steps, two intermolecular PTs, and an in-plane displacement of one monomer with respect to the other. The result of this so-called assisted intramolecular proton transfer is the formation of a dimer in which only one monomer is a keto-enol derivative, the other monomer being apparently unchanged, although it suffers significant structural rearrangements along the reaction coordinate. Quite importantly, this dimer is significantly stabilized upon Ca²⁺ association; therefore, while the most stable uracil dimers correspond systematically to associations involving only the diketo forms, in (uracil)₂Ca²⁺ complexes the most stable structures correspond to those in which one of the monomers is a keto-enol uracil isomer.     

Copper(II) complexes of 2-(pyrrolidinomethyl)- and 2-(3-pyrrolinomethyl)pyridine N-oxides

Summary This title pyridine N-oxides have been prepared and their copper(II) complexes isolated as perchlorate, tetrafluoroborate and nitrate salts. The ligands coordinatevia both the pyridine N-oxide oxygen and the amine nitrogen to give bis(ligand) complexes for the perchlorate and tetrafluoroborate salts. The nitrate solids have [CuL(NO₃)₂] stoichiometry with monodentate nitrato-ligands. The spectral properties of these complexes are compared to those of N-alkyl-and N,N-dialkyl2-picolinamine N-oxides as well as other 2-substituted pyridine N-oxides.NATO Fellow on leave from Istanbul Medical Faculty, Istanbul University.