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Recent advances in guanidinium-based receptors are summarized emphasizing the high affinity of the guanidinium moiety towards certain anions in highly competitive aqueous media. Particularly the in...

The reaction of UO2(OAc)2 ⋅ 2H2O with the biologically inspired ligand 2‐salicylidene glucosamine (H2 L1) results in the formation of the anionic trinuclear uranyl complex [(UO2)3(μ3‐O)(L1)3]2− (1 2−), which was isolated in good yield as its Cs‐salt, [Cs]2 1. Recrystallization of [Cs]2 1 in the presence of 18‐crown‐6 led to formation of a neutral ion pair of type [M(18‐crown‐6)]2 1, which was also obtained for the alkali metal ions Rb+ and K+ (M=Cs, Rb, K). The related ligand, 2‐(2‐hydroxy‐1‐naphthylidene) glucosamine (H2 L2) in a similar procedure with Cs+ gave the corresponding complex [Cs(18‐crown‐6)]2[(UO2)3(μ3‐O)(L2)3 ([Cs(18‐crown‐6)]2 2). From X‐ray investigations, the [(UO2)3O(Ln)3]2− anion (n=1, 2) in each complex is a discrete trinuclear uranyl species that coordinates to the alkali metal ion via three uranyl oxygen atoms. The coordination behavior of H2 L1 and H2 L2 towards UO2 2+ was investigated by NMR, UV/Vis spectroscopy and mass spectrometry, revealing the in situ formation of the 1 2− and 2 2−dianions in solution., Investigation of the coordination behavior of salicylidene glucosamine (H2 L1) towards uranyl ions (UO2 2+) revealed the exclusive formation of a trinuclear anionic uranyl complex [(UO2)3(μ3‐O)(L1)3]2− (1 2−), which was isolated by precipitation with the alkali metals ions Cs+, Rb+, and K+. Recrystallization of the Cs salt in the presence of 18‐crown‐6 in DMF led to the formation of the solvated ion pair [Cs(18‐crown‐6)]2 1, in which coordination of the Cs+ ion by three uranyl oxygen atoms was observe.

The leaching performance and leaching kinetics of LiFePO4 (LFP) and Al in Al-bearing spent LFP cathode powder were systematically studied. The effects of temperature (273−368 K), stirring speed (200−950 r/min), reaction time (0−240 min), acid-to-material ratio (0.1:1−1:1 mL/g) and liquid-to-solid ratio (3:1−9:1 mL/g) on the leaching process were investigated. The results show that the concentration of reactants and the temperature have a greater impact on the leaching of Al. Under the optimal conditions, leaching efficiencies of LFP and Al are 91.53% and 15.98%, respectively. The kinetic study shows that the leaching of LFP is kinetically controlled by mixed surface reaction and diffusion, with an activation energy of 22.990 kJ/mol; whereas the leaching of Al is only controlled by surface chemical reaction, with an activation energy of 46.581 kJ/mol. A low leaching temperature can effectively suppress the dissolving of Al during the acid leaching of the spent LFP cathode material.

Structural investigations of three actinide(IV) 4-phosphoryl 1H-pyrazol-5-olate complexes (An = Th(IV), U(IV), Np(IV)) and their cerium(IV) analogue display the same metal coordination in the solid state. The mononuclear complexes show the metal centre in a square antiprismatic coordination geometry composed by the two O-donor atoms of four deprotonated ligands. Detailed solid state analysis of the U(IV) complex shows that dependent on the solvent used altered arrangements are observable, resulting in a change in the coordination polyhedron of the U(IV) metal centre to bi-capped trigonal prismatic. Further, single crystal analyses of the La(III) and Ce(III) complexes show that the ligand can also act as a neutral ligand by protonation of the pyrazolyl moiety. All complexes were comprehensively characterized by NMR, IR and Raman spectroscopy. A single resonance in each of the 31P NMR spectra for the La(III), Ce(III), Ce(IV), Th(IV) and Np(IV) complex indicates the formation of highly symmetric complex species in solution. Extended X-ray absorption fine structure (EXAFS) investigations provide evidence for the same local structure of the U(IV) and Np(IV) complex in toluene solution, confirming the observations made in the solid state.

High-efficient and fast adsorption of uranium is important to reduce the hazards caused by the uranium contamination of water environment due to the increased human activities. Herein, brewer's spent grain (BSG)-supported superabsorbent polymers (SAP) with different cross-linking densities are prepared as cheap and eco-friendly adsorbents for the first time via one-pot swelling and graft polymerization. A 7 wt% NaOH solution is used to swell BSG before grafting and subsequently neutralize the acrylic acid to control the reaction rate without producing alkaline wastewater. Compared with the traditional methods, swelling improves the grafting density and the utilization of raw materials due to the increased disorder degree of the BSG fibers. This results in the grafting of abundant carboxyl and amide groups onto the BSG backbone, forming a strongly hydrophilic polymer network of the BSG-SAP. Compared with the reference polymers without BSG, BSG-SAP presents higher adsorption capacity and enhanced reusability. The highly cross-linked BSG-SAP (BSG-SAP-H) shows an outstanding adsorption capacity of U(VI) (1465 mg/g at pH

Detailed investigations of the reaction pathway to trinuclear oxo-bridged uranyl complexes.

Effective receptors for the separation of Li + from a mixture with other alkali metal ions under mild conditions remains an important challenge that could benefit from new approaches. In this study, it is demonstrated that the 4-phosphoryl pyrazolones, H L 2 -H L 4 , in the presence of the typical industrial organophosphorus co-ligands tributylphosphine oxide (TBPO), tributylphosphate (TBP) and trioctylphosphine oxide (TOPO), are able to selectively recognise and extract lithium ions from aqueous solution. Structural investigations in solution as well as in the solid state reveal the existence of a series of multinuclear Li + complexes that include dimers (TBPO, TBP) as well as rarely observed trimers (TOPO) and represent the first clear evidence for the synergistic role of the co-ligands in the extraction process. Our findings are supported by detailed NMR, MS and extraction studies. Liquid-liquid extraction in the presence of TOPO revealed an unprecedented high Li + extraction efficiency (78%) for H L 4 compared to the use of the industrially employed acylpyrazolone H L 1 (15%) and benzoyl-1,1,1-trifluoroacetone (52%) extractants. In addition, a high selectivity for Li + over Na + , K + and Cs + under mild conditions (pH ~ 8.2) confirms that H L 2 -H L 4 represent a class of ligands that are very effective extractants for use in lithium separation.

Structural investigations of three actinide(iv) 4-phosphoryl 1H-pyrazol-5-olate complexes (An = Th(iv), U(iv), Np(iv)) and their cerium(iv) analogue display the same metal coordination in the solid state. The mononuclear complexes show the metal centre in a square antiprismatic coordination geometry composed by the two O-donor atoms of four deprotonated ligands. Detailed solid state analysis of the U(iv) complex shows that dependent on the solvent used altered arrangements are observable, resulting in a change in the coordination polyhedron of the U(iv) metal centre to bi-capped trigonal prismatic. Further, single crystal analyses of the La(iii) and Ce(iii) complexes show that the ligand can also act as a neutral ligand by protonation of the pyrazolyl moiety. All complexes were comprehensively characterized by NMR, IR and Raman spectroscopy. A single resonance in each of the 31P NMR spectra for the La(iii), Ce(iii), Ce(iv), Th(iv) and Np(iv) complex indicates the formation of highly symmetric complex species in solution. Extended X-ray absorption fine structure (EXAFS) investigations provide evidence for the same local structure of the U(iv) and Np(iv) complex in toluene solution, confirming the observations made in the solid state.

Spent hydrodesulfurization (HDS) catalysts, containing considerable amount of pollutants and metals including vanadium (V), molybdenum (Mo), aluminum (Al), and nickel (Ni), are considered as hazardous wastes which will result in not only ecosystem damage but also squandering resource. Herein, a process featuring blank roasting-alkaline leaching is proposed to recover spent HDS catalyst. During roasting, low-valence compounds convert to high-valence oxides which can be leached out by NaOH solution. Afterwards, leaching solution is subjected to crystallization to separate metals. The results show that for samples roasted at 650 °C, 97% V, 96% Mo, and 88% Al are leached out at optimal condition; for samples roasted at 1000 °C, selective leaching of 91% V and 96% Mo respectively, are realized, with negligible Al being dissolved. NiO is insoluble in strong alkali leaving in residue. The advantages of this process are that first, the leaching of V, Mo, and Al can be manipulated by controlling roasting conditions, providing flexible process design. Second, leaching solution can be fully recycled. Finally, mild leaching condition and clean separation of V, Mo, and Al is achieved, proving fundamental information for peer researches to facilitate their future research on the development of more efficient and cleaner technologies.

The increasing concerns on uranium and rare earth metal ion pollution in the environment require sustainable strategies to remove them from wastewater. The present study reports an eco-friendly approach to convert a kind of protein-rich biomass, brewer's spent grain (BSG), into effective biosorbents for uranyl and rare earth metal ions. The employed method reduces the energy consumption by performing the hydrothermal treatment at a significantly lower temperature (150 °C) than conventional hydrothermal carbonization. In addition, with the aid of the Maillard reaction between carbohydrates and proteins forming melanoidins, further activation processes are not required. Treatment at 150 °C for 16 h results in an altered biosorbent (ABSG) with increased content of carboxyl groups (1.46 mmol g

In Vietnam, Dzung Quat Refinery disposes about 7300 tonnes of spent fluid catalytic cracking (SFCC) catalysts per year. The recovery of rare earth metals (La(III), Ce(III),…) contained in SFCC catalysts using acid leaching process has attracted much attention of scientific community. In this study, the effect of alkaline pre-treatment of spent catalysts prior to the acid leaching process on the leaching yield of La(III) was investigated. The results showed that alkaline pre-treatment caused zeolite destruction, which had a positive effect on the leaching of La(III). High leaching yields of La(III), 80% and 86%, were achieved when the SFCC catalysts were pre-treated with NaOH and NH3, respectively, before leaching with 2 M HNO3 solution at 50 °C. These results were comparable with the one obtained from the sample that was leached by 7 M HNO3 at 50 °C without the initial alkaline pre-treatment. NH3 pre-treatment significantly enhanced the zeolite destruction in the SFCC catalysts and increased La(III) leaching yield compared to the NaOH pre-treatment. It is likely due to NH3 interactions with contaminant metals (e.g. Ni, V, and Fe), which were deposited on catalysts during cracking process.

Acid leaching and a two-step solvent extraction procedure were developed to produce high purity mixture of La and Ce from iron-rich spent FCC catalyst discharged from Dzung Quat refinery (Vietnam). Acid leaching of the spent catalyst with 2M HNO3 and a solid-to-liquid ratio of 1/3 at 80 °C in 1 h dissolved almost 90% of La while 12% of Al and 25% of Fe were transferred to the leachate. The extraction of RE metals and main impurities such as Al and Fe by a mixture of di-2-ethylhexyl phosphoric acid (D2EHPA) and tributyl phosphate (TBP) was investigated. Experiments showed that it was necessary to remove Fe before extracting RE and the optimum extraction conditions for a high recovery of RE while 0% of Al extraction were pH-1, contact time=10min, and D2EHPA/TBP volume ratio= 4: 1. At these conditions, the extraction yields of La(III) and Ce(III) were 72% and 89%, respectively. A two-step solvent extraction was developed to achieve a high purity of RE mixture, which included (1) the removal of impurity Fe by 25% (v/v) diisooctyl phosphinic acid (DiOPA) in n-octane for 140 min, (2) the extraction of rare earths by a mixture of di-2-ethylhexyl phosphoric acid (D2EHPA) and tributyl phosphate (TBP) in n-octane for 10 min without the need for adjusting the pH of the leaching solution.

The conveniently prepared N,N′-dialkylsubstituted urea derivative, 1-butyl-3-(2-ethylhexyl)urea (L), was prepared and elucidated with respect to its performance as an extractant for [PtCl6]2− from HCl solutions. L effectively extracts Pt(IV) and Pd(II) from 0.01 to 10 M HCl solutions with a high selectively over metal ions (Rh(III), Ir(III), Fe(III), Cu(II), Ni(II), Co(II), Zn(II), and Pb(II)) in the concentration range from 0.3 to 1.0 M HCl solutions. According to a slope analysis, the extraction equilibrium reaction of Pt(IV) by L was determined to be [PtCl6]2−aq. + 2Lorg. + 2HClaq. ↔ (PtCl62−)·(HL+)2org. + 2Cl−aq., which is a typical ion-pair reaction. Ultraviolet–visible measurements proved that Pt(IV) was extracted into the organic phase by L as a [PtCl6]2− salt. 195Pt nuclear magnetic resonance (NMR) investigation suggests that the Pt(IV) extracted by L has slightly lower electron density on the Pt(IV) ion compared with the Pt(IV) species extracted by the conventional extractant tri-n-octylamine from HCl solution. Infrared and 1H NMR spectroscopic measurements revealed a strong hydrogen bonding between the Cl− ligands of [PtCl6]2− and the N–H protons of L in the organic phase. Analysis of the water content in the organic phase, before and after the [PtCl6]2− extraction, shows that 0.9–2.6 water molecules are released from the organic phase as the result of [PtCl6]2− extraction from the aqueous into the organic phase by L.

This micro review covers recent advances in anion recognition, such as selective developments in the receptor design. Applications to which anion receptors can be applied, for example anion extraction and transport, are highlighted.

Recycling the end-of-life lithium-ion batteries including the lithium iron phosphate (LiFePO4) battery has been one of the most important technology areas since electric vehicles are gradually dominating the way of transportation. For the recycling of LiFePO4 batteries, the regeneration of pure iron phosphate dihydrate (FePO4 center dot 2H(2)O) from spent cathode material is essential but difficult. The challenge is how to effectively synthesize battery-grade iron phosphate from the impurity-bearing acid solution by precipitation since the spent cathode powder usually holds various impurities. To avoid the introduction of impurities into the iron phosphate, a one-step spontaneous precipitation and phase transformation mode without acidity adjustment was preferred and studied in this work. The focus of this research included the process of phase transformation from amorphous to crystalline, and its effects on precipitation and the properties of the precipitate. It was interestingly found that there was an induction period for phase transformation from amorphous FePO4 center dot xH(2)O to monoclinic FePO4 center dot 2H(2)O during the precipitation, which was distinctly shortened with the elevated temperature. Phase transformation led to fast increased precipitation efficiency, morphology evolution, and composition change, which benefited the consistency of iron phosphate. Phase transformation could be kinetically described by the JMA equation, with a rate-limiting step of materials diffusion towards the nucleation point and an activation energy of 20.4 kJ/mol. The critical crystal size for transformation was increasing along with the temperature's raising, which was ascribed to the changes in the volume energy and the surface energy. The results in this study have built the feasibility of chemically regenerating FePO4 center dot 2H(2)O precursors from the spent cathode powder by precipitation purification in an acidic medium. (C) 2020 Elsevier B.V. All rights reserved.

Purification of vanadium products by removal of chromium compounds, especially at high pH, remains a challenging task. In this contribution, purification of sodium vanadate solutions by selective solvent extraction of Cr(VI) from strong alkaline aqueous solution (initial pH 12 and above) was investigated, and the mechanisms governing the selectivity of quaternary ammonium salt Aliquat 336 were studied and discussed in detail. The influence of critical technological parameters including pH of the feed solution, added modifier, diluent, and contact time were examined and analyzed systematically. The experiments reveal a high extraction power for Cr(IV) using Aliquat 336 in the presence of TBP, realizing no extraction of V(V) under optimized condition. Stripping of Cr(VI) from the loaded organic phase was furthermore evaluated. The present work highlights a new approach to separate Cr(VI) from strong alkaline solution with a high degree of selectivity which enables the achievement of a high purity sodium vanadate.

Vanadium is an important strategic metal and has been widely applied in a multiple of industries. However, the current process for the production of vanadium compounds suffers from the generation of a significant amount of high salinity ammonium containing wastewater due to the mixing of sodium salts, ammonium salts, and acid during vanadium precipitation operation. In order to avoid the generation of wastewater at source, a clean and recyclable V2O5 production process was proposed and investigated in this study. Using NH4VO3 and NH3·H2O as precipitants, (NH3)2·3V2O5·H2O and (NH3)2·V2O5·H2O were obtained by precipitation of vanadate (VxOyn−) from a high vanadate to sodium (V/Na) molar ratio acidic solution obtained via membrane electrolysis method, avoiding the generation of wastewater or solid waste. After calcination, high purity V2O5 product could be obtained. The vanadium precipitation process was investigated using ICP, XPS, SEM, XRD techniques, and the precipitation rate was investigated using solution conductivity method. Critical precipitation parameters such as excessive coefficient, solution temperature, solution V/Na molar ratio and solution pH were examined in detail. The results showed that increase the excessive coefficient, solution temperature and solution V/Na molar ratio, as well as reduce the solution pH would be beneficial for obtaining high purity vanadium products (≥99.9% V2O5). Optimum parameters were obtained at the V/Na molar ratio of 2.58, the excessive coefficient of 2, and the solution temperature of 363 K. The vanadium products obtained using both precipitants have a similar purity (more than 99.9%), however, due to a higher degree of hydrolysis reaction, the NH4VO3 precipitation method showed a higher VxOyn− precipitation rate (66.36%) in comparison with the NH3·H2O precipitation method (38.76%), indicating that the first method was superior. Based on this, a complete process with zero waste emission for V2O5 production was designed. The methods proposed and the results obtained from this study could provide fundamental information for the design of cleaner vanadium production process.

An efficient method for recovering and separating Ce3+ and La3+ rare earth elements from spent fluid catalytic cracking (FCC) catalyst is described. Initially, the spent FCC catalyst was leached with 2 M HNO3 at 80 °C then removal of iron from the leach solution was carried out by solvent extraction with 25% (v/v) diisooctyl phosphinic acid (DiOAP) in n-octane. Extraction of the above rare earths was then undertaken from the nitric acid leach solution using an organic phase consisting of 25% (v/v) di(2-ethylhexyl) phosphoric acid (D2EHPA) and 25% (v/v) tri-n-butyl phosphate (TBP) in n-octane. Both rare earths were stripped form the organic phase using H2SO4. Separation of the Ce3+ from La3+ was then achieved by means of an in situ electrochemical oxidation coupled with a simultaneous solvent extraction process. In this, the Ce3+ was electrochemically oxidized to Ce4+ and removed from the aqueous phase by solvent extraction employing 100 mM D2EHPA in n-octane. This led to efficient separation of the above rare earths, giving rise to La3+ in high purity of up to 99.5% and Ce4+ up to 100%. The separation occurs via a single extraction step without the need for pH adjustment or for the use of additional reagents.

Reaction of equimolar amounts of Cu(OAc)2·H2O and bis[4-(3-ethoxysalicylideneamino)phenyl]methane (H2L1) or bis[4-(3-ethoxysalicylideneamino)phenyl]sulfide (H2L2) in a 1:1 THF/MeOH mixture leads to the formation of structure-analogous CuII helicates of the composition [{Cu2L2}(H2O)2}]·4H2O. The helicates form left- and right-handed hydrogen bonded strands using the bound water molecules as glue. Finally, a compact 3D arrangement of the molecules is achieved by weak π···π and CH···π interactions. The CuII ions possess a strongly distorted tetrahedral arrangement with a N2O2 donor set of the involved diimines. In addition, the molecular structure of the ligand H2L2 was determined and solution studies of the complex formation using UV/Vis and ESI-MS were performed.

Tripodal extraction reagent with three phosphoric acid groups, together with the corresponding monopodal molecule has been prepared to investigate some metals extraction behavior, in particular, trivalent rare earth elements (REEs). The tripodal reagent exhibited extremely high selectivity for metals with high valency such as Zr(IV), In(III), Lu(III), and Fe(III). Tripodal reagent also exhibited exceptionally high extraction ability compared with the corresponding monopodal one in the extraction of trivalent rare earths. The result for the stoichiometry of tripodal reagent to heavy rare earths showed the inflection point between Er (2:1 for a ligand with ion) and Tm (1:1). The extraction reactions were determined for all rare earths with both reagents. The extraction equilibrium constants (Kex), the separation factors (β), half pH values (pH1/2), difference half pH values (ΔpH1/2) for extraction of REEs with both reagents are estimated.

Thick-Film Resistors (TFR) are applied for many years for the manufacturing of ceramic electronic packages as well as for mechanical or thermal sensors. The resistors characteristics (e.g. Rsqr, HTCR, CTCR) are guaranteed by paste suppliers for a thermal range of operation between −55 and 125°C. However, specific sensor applications require higher operation temperatures of up to 500°C. In the paper the results of the characterization of commercial TFR at elevated temperatures on alumina substrates are presented. Electrical characteristics (e.g. Rsqr, HTCR, CTCR, GF) are correlated with materials characteristics (TFR thermal expansion, glass transition temperature, microstructure). Different requirements are discussed regarding an improved high temperature applicability of TFR. Advantages and limits of the commercial TFR will be presented.

An approach for accurate and comparable measurement of host-guest binding affinities is introduced whereby differences in binding strength (ΔlogKass values) are measured between two host molecules toward a particular guest under identical solvent conditions. Measuring differences instead of absolute values enables obtaining highly accurate results, because many of the uncertainty sources (the solvation/association state of the guest in solution, deviations in solvent composition, etc.) cancel out. As a proof of concept, this method was applied to the measurement of the binding strength of 28 synthetic anion receptors toward acetate in acetonitrile containing 0.5% water. The receptors included differently substituted indolocarbazoles, ureas, thioureas, and some others. Possible deprotonation of more acidic receptors of each compound class by acetate was checked by measuring their acidities (ΔpKa values) relative to acetic acid in the same solvent. A self-consistent (consistency standard deviation 0.04 log units) binding affinity scale ranging for around 2.7 log units was constructed from the results. Absolute logKass values were found by anchoring the scale to the absolute logKass values of two receptor molecules, determined independently by direct measurements. This new approach is expected to find use in accurate quantification of a wide range of binding processes relevant to supramolecular chemistry.

We report the synthesis, crystal structures and ESR measurements of two new copper(II) complexes having the general formula [Cu(1)(CH3CN)3](ClO4)2 involving the ligands 4,9-dichloroquino[7,8-h]quinoline 1a and quino[7,8-h]quinoline 1b.

New conductor pastes for AlN as substrate material with fired films of a sheet resistance below 25 mOhm/sq were investigated. The pastes consist of AgPd as conductive phase for leach resistance. Other paste ingredients are glasses of matched composition for adhesion and densification properties, little amounts of inorganic additives and organic vehicles for film deposition. The latter has a significant influence on the paste deposition and the resulting film properties as well. In order to shine light into these relationship systematic rheological studies of the organic vehicle and the manufactured pastes were performed. The rheological investigations include measurements in rheological steady-state as well as dynamic experiments. In addition, the solder properties of the fired film were studied. FESEM analyses were performed on the surface of the fired films.

A new route to unsymmetrical derivatives of quino[7,8-h]quinoline was developed. Substitutions at the 2,11-, 4,9- and 6,7-positions of quino[7,8-h]quinoline were also successfully performed. X-ray crystal structure determinations of the resulting products revealed the propensity for derivatives of this molecule to exist in either stabilised keto or imino forms as a result of the formation of a strong intramolecular N–H···N hydrogen bond.

We report a milder synthetic route for the compounds 4,9-dichloroquino[7,8-h]quinoline L1 and quino[7,8-h]quinoline L2 and we utilise these ligands in the synthesis of boron difluoride chelates. X-ray crystallographic analysis of L1, [HL1]BF4 and the coordinated structures of [BF2L1]BF4 and [BF2L2]BF4 reveal the flexible nature of the ligand.

4,4′-biphenylene spaced lipophilic bis-β-diketone ligands of the type 4,4′-bis(RC(O)CH2C(O))C12H8 (R = Pr, Ph, hexyl, octyl, nonyl) have been prepared and used for the liquid–liquid extraction of d-block metal ions. These ligands are expected to interact with divalent metal ions to form charge-neutral trinuclear metallocycles of type [M3(L3)3(solvent)] as has been demonstrated with the previously reported derivative of H2L3 (R = tBu), the X-ray structure of which is reported. Liquid–liquid extraction studies were performed in a two-phase water/chloroform system employing a radiotracer technique for cobalt(II) and zinc(II). These experiments involved the systematic variation of ligand, metal and 4-ethylpyridine concentrations to probe the stoichiometries of the species extracted. Synergistic extraction was observed when 4-ethylpyridine was present with the ligand in the organic phase. Competitive extraction studies demonstrated the ligands are highly selective for copper(II) over cobalt(II), nickel(II), zinc(II) and cadmium(II).

A previously unseen coordination mode is reported for (salicylaldoxime)copper complexes utilising a linked zwitterionic NO22– donor set. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

1,4- (H₂L¹) and 1,3-phenylene (H₂L²) linked bis-β-diketone ligands as well as corresponding metal complexes of composition M₃(L¹)₃B₆ and M₂(L²)₂B₂ with B = pyridine (Py) or 4-ethylpyridine (EtPy) have been synthesised. Extraction studies involving the systematic variation of the metal, bis-β-Bdiketone and 4-ethylpyridine concentrations have been performed for Co(Il) and Zn(II) in order to probe the solution stoichiometries of the extracted species. Significant synergistic effects were observed when EtPy was present along with the bis-β-diketone ligand in the organic (CHCI₃) phase. Competitive extraction studies (water/chloroform) demonstrated a clear uptake preference for Cu(II) over Co(II), Ni(II), Zn(Il) and Cd(II).

Interaction of copper(II) salts with 2,2′-dipyridylamine (1), N-cyclohexylmethyl-2,2′-dipyridylamine (2), di-2-pyridylaminomethylbenzene (3), 1,2-bis(di-2-pyridylaminomethyl)-benzene (4), 1,3-bis(di-2-pyridylaminomethyl)benzene (5), 1,4-bis(di-2-pyridylaminomethyl)benzene (6), 1,3,5-tris(di-2-pyridylaminomethyl)benzene (7) and 1,2,4,5-tetrakis(di-2-pyridylaminomethyl)benzene (8) has yielded the following complexes: [Cu(2)(μ-Cl)Cl]2, [Cu(3)(μ-Cl)Cl]2 · H2O, [Cu2(4)(NO3)4], [Cu2(5)(NO3)4] · 2CH3OH, [Cu2(6)(CH3OH)2(NO3)4], [Cu4(8)](NO3)4] · 4H2O while complexation of palladium(II) with 1, 4, 5 and 6 gave [Pd(1)2](PF6)2 · 2CH3OH, [Pd2(4)Cl4], [Pd2(4)(OAc)4], [Pd2(5)Cl4], [Pd2(6)Cl4] and [Pd2(6)(OAc)4] · CH2Cl2, respectively. X-ray structures of [Cu(2)(μ-Cl)Cl]2, [Cu(3)(μ-Cl)Cl]2 · 2C2H5OH, [Cu2(6)(CH3OH)2(NO3)4], [Pd(1)2](PF6)2 · 2CH3OH, [Pd2(4)(OAc)4] · 4H2O and [Pd2(6)(OAc)4] · 2CH2Cl2 are reported. In part, the inherent flexibility of the respective ligands has resulted in the adoption of a diverse range of coordination geometries and lattice arrangements, with the structures of [Pd2(4)(OAc)4] · 4H2O and [Pd2(6)(OAc)4] · 2CH2Cl2, incorporating the isomeric ligands 4 and 6, showing some common features. Liquid–liquid (H2O/CHCl3) extraction experiments involving copper(II) and 1–3, 5, 7and 8 show that the degree of extraction depends markedly on the number of dpa-subunits (and concomitant lipophilicity) of the ligand employed with the tetrakis-dpa derivative 8 acting as the most efficient extractant of the six ligand systems investigated.

Two new mixed aza-thia crowns 5-aza-2,8-dithia[9]-(2,9)-1,10-phenanthrolinophane (L(4)) and 2,8-diaza-5-thia[9]-(2,9)-1,10-phenanthrolinophane (L(7)) have been synthesized and characterized. The coordination behavior of L(4) and L(7) toward the metal ions Cu(II), Zn(II), Pb(II), Cd(II), Hg(II), and Ag(I) was studied in aqueous solution by potentiometric methods, in CD3CN/D2O 4:1 (v/v) by (1)H NMR titrations and in the solid state. The data obtained were compared with those available for the coordination behavior toward the same metal ions of structurally analogous mixed donor macrocyclic ligands L(1)-L(3), L(5), L(6): all these contain a phenanthroline subunit but have only S/O/N(aromatic) donor groups in the remaining portion of the ring and are, therefore, less water-soluble than L(4) and L(7). The complexes [Cd(NO3)2(L(5))], [Pb(L(7))](ClO4)2 x 1/2MeCN, [Pb(L(4))](ClO4)2 x MeCN, and [Cu(L(7))](ClO4)2 x 3/2MeNO2 were characterized by X-ray crystallography. The efficacy of L(1)-L(7) in competitive liquid-liquid metal ion extraction of Cu(II), Zn(II), Cd(II), Pb(II), Ag(I), and Hg(II) was assessed. In the absence of Hg(II), a clear extraction selectivity for Ag(I) was observed in all systems investigated.

The study of the complex formation of 3,3-diphenyl-3H-benzo[f]chromenes containing aza-18-crown-6-ether, diaza-18-crown-6-ether or morpholine units with alkali, alkaline earth, heavy and transition metal cations in acetonitrile is reported. The spectroscopic and kinetic behavior of the photomerocyanine isomers of these chromenes is strongly affected by complexation with a metal cation. In order to interpret some of experimental data, an ab initio theoretical analysis of photochromic-crown ether and its cation complexes was conducted. The different site of coordination of mono- and divalent cations to determine the minimum-energy structure of benzochromene complexes in gas phase as well as in acetonitrile as solvent was explored. The coordination of both carbonyl oxygen and crown-ether macrocyle with divalent cations in carbonyl-capped structure is found to be the most stable isomer in gas as well as in condensed media. The crown-containing benzochromenes were studied in liquid-liquid extraction experiments toward there capacity to transfer metallic salts from water into an organic phase.The high selectivity to extraction of Ag+ was found. Copyright © 2007 John Wiley & Sons, Ltd.

The syntheses and single crystal X-ray analyses of five strapped salicylaldoxime/salicylaldimine based dicopper(II) receptors utilising a new piperazine linker are described. The complexes 1–4 form 2 + 2 metallocycles and the molecular structures of all four complexes possess a small internal cavity with the utilisation of a short piperazine linker. The molecular structures of complexes [Cu2(L4 − H)(L4 − 2H) ⊂ DMF]BF4·DMF, 1 and [Cu2(L4 − H)2Br]Br·1.25DMSO·H2O·MeOH, 2 show that intramolecular H-bonding interactions due to the presence of –OH (oxime moiety) groups lead to a Pacman-like cleft arrangement of the two metal coordinating subunits in the metallo-macrocycle. The geometrical constraints brought about by this constrained cleft make the receptor coordinate strongly to a bromide anion involving both metal centres as evidenced by 2 whereas in 1 the larger tetrafluroborate anion is excluded. Absence of the oxime moiety around the metal coordination site of the ligand as demonstrated in the complexes [Cu2(L5)2BF4](BF4)3, 3 and [Cu2(L5)2Br]Br3·2MeOH, 4 resulted in less constrained dicopper(II) helicate forms. For these complexes no anion size discrimination was observed. The addition of pyridine solvent to a slightly modified piperazine-linked ligand produces an expanded 3 + 3 tube-like tricopper complex [Cu3(L4a − H)3Py3](BF4)2·(MeOH)3·PF6·(H2O)3, 5, with two coordinated pyridine molecules occupying the newly formed cavity.

In the discussion that follows some of the more recent progress in the area of anion binding by synthetic polyamine receptors is presented, with emphasis given to work undertaken by the authors’ groups. A continuing theme in these studies has been the relationship between receptor structure and its anion extraction properties. Systematic solvent extraction and structural studies for halide and perrhenate complexes with polyamines of tripodal, macrocyclic and macrobicyclic architecture that contain both aromatic moieties and four to eight amine functions have been performed in order to derive relevant structure-binding/extractability relationships. The results demonstrate that the binding and extraction behaviour of the polyamines towards halides and perrhenate is a complex function of their structural features, degree of protonation and lipophilic properties. The extraction is characterized by the preferred formation of mono- and diprotonated amine species in the organic phase. X-ray structure studies of iodide and perrhenate complexes with open-chain tetraamino derivatives and octaamino cryptands in different protonation states lead to the conclusion that in the first case only limited chelation of the anion occurs and in the second only highly protonated species are able to encapsulate the anion. The structural patterns observed are strongly influenced by the presence of water molecules in the crystals.

A comparative study on Zn 2+ and Cu 2+ complexes of the novel compound 5,11,17,23-tetra- tert -butyl-25,27-bis{[4-(methoxycarbonyl)phenyl]methoxy}-2,8,14,20-tetrathiacalix[4]arene, that possesses potential as a core unit for the construction of molecular receptors, is presented using semiempirical AM1 calculation. The possible structures of each metal complex and their corresponding energetic data are compared with the parent 5,11,17,23-tetra- tert -butyl-2,8,14,20-tetrathiacalix[4]arene. The complexation ability of both thiacalix[4]arenes towards the two metal ions is discussed on the basis of binding energies. Both thiacalix[4]arene 1:1 complexes show higher complexation ability towards Cu 2+ . However, 5,11,17,23-tetra- tert -butyl-25,27-bis{[4-(methoxycarbonyl)phenyl]methoxy}-2,8,14,20-tetrathiacalix[4]arene presents lower complexation ability when compared with the 5,11,17,23-tetra- tert -butyl-2,8,14,20-tetrathiacalix[4]arene. The results of liquid–liquid extraction experiments of the thiacalix[4]arenes are in good agreement with the theoretical calculations.

Synthesis of the 2,2'-dipyridylamine derivatives di-2-pyridylaminomethylbenzene 1, 1,2-bis(di-2-pyridylaminomethyl)benzene 2, 1,3-bis(di-2-pyridylaminomethyl)benzene 3, 2,6-bis(di-2-pyridylaminomethyl)pyridine 4, 1,4-bis(di-2-pyridylaminomethyl)benzene 5, and 1,3,5-tris(di-2-pyridylaminomethyl)benzene 6 are reported together with the single-crystal X-ray structures of 2, 3, and 5. Reaction of individual salts of the type AgX (where X = NO(3)(-), PF(6)(-), ClO(4)(-), or BF(4)(-)) with the above ligands has led to the isolation of thirteen Ag(I) complexes, nine of which have also been characterised by X-ray diffraction. In part, the inherent flexibility of the respective ligands has resulted in the adoption of a range of coordination arrangements. A series of liquid-liquid (H(2)O/CHCl(3)) extraction experiments of Ag(I) with varying concentrations of 1-6 in the organic phase have been undertaken, with the counter ion in the aqueous phase being respectively picrate, perchlorate and nitrate. In general, extraction efficiencies for a given ionophore followed the Hofmeister order of picrateperchloratenitrate; in each case the tris-dpa derivative 6 acting as the most efficient extractant of the six systems investigated. Competitive seven-metal bulk membrane transport experiments (H(2)O/CHCl(3)/H(2)O) employing the above ligands as the ionophore in the organic phase and equimolar concentrations of Co(II), Ni(II), Zn(II), Cu(II), Cd(II), Pb(II) and Ag(I) in the aqueous source phase were also undertaken, with transport occurring against a pH gradient. Under the conditions employed 1 and 5 yielded negligible transport of any of the metals present in the source phase while sole transport selectivity for Ag(I) was observed for 2-4 and 6.

In this paper, we present an experimental localization system consisting of two fused solutions. The Ultra-wideband Localization Platform based on the time difference of arrival technique provides accurate positioning in a limited indoor area. The wireless sensor network s-net® system, calculating positions with the weighted centroid localization algorithm by the use of received signal strength indication technique provides coarse localization within a whole floor. The evaluation scenario covers one of the potential system applications — asset tracking in medical facilities.