Synthesis and crystal structure of copper and gold complexes of 1,2,5-thiadiazole-3,4-dithiolate. Charge transfer salt with TTF

The M(tdas)₂ complexes (tdas²⁻=1,2,5-thiadiazole-3,4-dithiolate) with M=Cu^II, Cu^III and Au^III were obtained as tetrabuthylammonium and tetraphenilphosphonium salts and characterised. The crystal structure of (n-Bu₄N)n[M(tdas)₂], M=Cu(2) and Au(4) were determined by X-ray crystallography as well as that of the charge transfer salt (TTF)₂[Au(tdas)₂]₂ (5).     

Electrical and Spectroscopic Properties of TTF and TSF Salts with Tetrahalogenozinc(II) and -cadmium(II) Anions

Several tetrathiafulvalene (TTF) and tetraselenafulvalene (TSF) salts of tetrahalogenozinc(II) and -cadmium(II) anions D_x [MX₄] (D = TTF or TSF; M = Zn and Cd; X = Cl, Br, and I; x = 2.0-6.6) have been prepared by the reaction of [TTF]₃[BF₄]₂ or [TSF]₃[BF₄]₂ with [NEt₄]₂[MX₄] in acetonitrile and by the electrolysis of TTF or TSF in acetonitrile containing [NEt₄]₂[MBr₄]. Electrical resistivities of these salts measured for compressed pellets fall in the range 1 × (10¹–10⁷) Ω cm at 25 °C; the value decreases with increasing bulkiness of the anions: [MCl₄]^2– > [MBr₄]²⁻ > [MI₄]²⁻. Stackings and electronic states of TTF and TSF molecules are discussed on the basis of electronic reflectance, ESR, IR, and Raman spectra.     

Change in the molecular weight distribution of poly(ethylene oxide) caused by the complexation with poly(acrylic acid)

The complexation between poly(ethylene oxide) (PEO) and poly(acrylic acid) (PAA) was made by using double the molar quantity of either polymer component at pH 2 where the resulting complex completely precipitates. After the removal of the precipitate, PEO or PAA remaining in the supernatant was subjected to gel permeation chromatography to investigate the change in the molecular weight distribution (MWD) caused by the complexation. No remarkable difference is observed in the MWD curves for PEO[1] (M_w=1.37 × 10⁴) before and after the complexation with PAA[1] (M_w=1.10 × 10³) and PAA[2] (M_w=4.16 × 10⁵). However, the MWD curves of PEO[2] (M_w=1.26 × 10⁵) and PAA[2] become shortened and shift to the low molecular weight side after the complexation with PAA[1] or [2] and PEO[2], respectively. This tendency is enhanced by increasing the complexation temperature. From these results, it is indicated that the complexation between PEO and PAA deals with an equilibrium reaction, and the equilibrium constant is dependent on the chain length of both polymer components and also on the complexation temperature.     

Zirconium tetra-n-butylate modified with different organic acids: Hydrolysis and polymerization of the products

In this work; (a) complexation reaction of zirconium tetra-n-butylate, Zr(OBu ⁿ )₄, with MAc and different organic acids. (b) the hydrolysis reaction of modified Zr species, and (c) the polymerization reaction of complex products are studied. Zr(OBu ⁿ )₄ was reacted with different mole ratios of methacrylic acid (MAc) at room temperature and the maximum combination ratio was found to be 1∶2 [Zr(OBu ⁿ )₄∶MAc] by FT IR. The modification of zirconium tetra-n-butylate with the acid mixtures [methacrylic acid-acetic acid (MeCOOH), methacrylic acid-propionic acid (EtCOOH), methacrylic acidbutyric acid (PrCOOH)] was made for a combination ratio of 1∶1∶1 [MAc∶RCOOH∶Zr(OBu ⁿ )₄∶R∶Me. Et, Pr] and the products were characterized by¹H-NMR, FT-IR, and UV-spectroscopies. Following their synthesis, hydrolysis of the complexes with various amounts of water and polymerization with benzoyl peroxide were realized. The hydrolysis and polymerization products of the complexes were studied by Karl-Fischer Coulometric titration and thermal analysis respectively. Methyl-ethyl-ketone (MEK) and chloroform were chosen as solvents.     

Zirconium tetra-n-butylate modified with different organic acids: Hydrolysis and polymerization of the products

In this work, (a) complexation reaction of zirconium tetra-n-butylate, Zr(OBu ⁿ )₄, with MAc and different organic acids, (b) the hydrolysis reaction of modified Zr species, and (c) the polymerization reaction of complex products are studied. Zr(OBu ⁿ )₄ was reacted with different mole ratios of methacrylic acid (MAc) at room temperature and the maximum combination ratio was found to be 1:2 [Zr(OBu ⁿ )₄:MAc] by FT-IR. The modification of zirconium tetra-n-butylate with the acid mixtures [methacrylic acid-acetic acid (MeCOOH), methacrylic acid-propionic acid (EtCOOH), methacrylic acid-butyric acid (PrCOOH)] was made for a combination ratio of 1:1:1 [MAc:RCOOH:Zr(OBu ⁿ )₄; R: Me, Et, Pr] and the products were characterized by¹H-NMR, FT-IR, and UV spectroscopies. Following their synthesis, hydrolysis of the complexes with various amounts of water and polymerization with benzoyl peroxide were realized. The hydrolysis and polymerization products of the complexes were studied by Karl-Fischer coulometric titration and thermal analysis, respectively. Methyl ethyl ketone(MEK) and chloroform were chosen as solvents.     

Zum Einfluß von arylständigen Substituenten auf die Komplexbildung von Monobenzokronenethern mit Alkalimetallionen in Methanol und Aceton

Influence of Aryl-bonded Substituents on Complex Formation of Benzocrown Ethers with Alkali Metal Ions in Methanol and Acetone Solutions The influence of aryl-bonded substituents upon the complex formation of monobenzocrown ethers towards alkali metal ions in methanol and acetone solutions are investigated by using calorimetric and potentiometric titration. A different complexation behaviour of the ligands in acetone and methanol was found. In the case of the 1:1 complexation of Na⁺ a correlation between substiuent effects and stability constants in acetone was noticed, however, the influence of substituents upon complex stability is weak. In methanol solutions no similar correlation could be established. During sandwich complexation of K⁺ in methanol, no significant substituent influences on K₁ and K₂ were observed. On the other hand, a considerable increase of ΔH₂ for both the electron accepting and electron releasing substituents was found, probably caused by changes in ligand-cation solvation due to the substituents.     

Conjugated opto/electroactive ethynylene-carbazole polymers with TTF as pendant group

Three conjugated ethynylene-carbazole polymers with Tetrathiafulvalene (TTF) as pendant group (P1–P3) were synthesized by using sonogashira coupling reaction and characterized by ¹H NMR, GPC, CV, UV–Vis, FL, and TGA. CV and UV–Vis spectra showed that an intramoleular interaction existed between the electron-rich moiety TTF and electron-deficient moiety polyethynylcarbazole of the polymers. A strong fluorescence quench (ca. 99%) could be observed, compared to the polyethynylene-carbazole without TTF units, which could be ascribed to the photo-induced electron transfer (PET) interaction from TTF moiety to the polyethynylene-carbazole backbone. The observed onset decomposition temperatures (T _d) for P1–P3 varied from 256 to 298 °C. The polymers mentioned above exhibited good thermal properties and higher conductivity (neutral conductivity ~7–11 × 10⁻⁷ S cm⁻¹; doped conductivity ~6–11 × 10⁻⁴ S cm⁻¹).     

Reduction electrochimique des cations complexes formes par dissolution dans le N,N-dimethylformamide des sels de chrome du type CrX3, 6H2O (X = Cl,Br, ClO4)

The electrochemical reduction of different cations formed by the solubilization of hexahydrated chromium salts in DMF was studied by polarography and cyclic voltammetry on stationary mercury dropping electrode, with tetrabutylammonium tetrafluoroborate 0.2 M as an indifferent electrolyte.The nature of the cations formed by water—DMF ligand exchange in the chromium complexation sphere depends on the nature of X(X = Cl, Br, ClO₄).The reduction potentials and some electrochemicals kinetics parameters of [Cr(DMF)₆]³⁺, [Cr(H₂O)₆]³⁺, [Cr(DMF)₅Br]²⁺, [Cr(DMF)₄Cl₂]⁺ and [Cr(DMF)₃Cl₃] were determined as well as exchange reactions between these electroactive species which may be simultaneously present either in solution or at the electrode.     

Electrochemical parametrization of a series of penta- and tetradentate EDTA complexes of ruthenium

This paper reports on the electrochemical parametrization of a series of mono- and disubstituted ruthenium–EDTA complexes (EDTA = ethylenediamine-N,N,N^′,N^′-tetraacetate ligand) on the basis of Lever’s parameters (E_L). The electrochemical parameters for 45 ligands with unknown E_L have been compiled.     

Dy(III) sorption from water solutions by mesoporous silicas functionalized with phosphonic acid groups

The sorption properties towards dysprosium(III) ions of three samples of mesoporous silicas functionalized with phosphonic groups????Si(CH₂)₂P(O)(OH)₂ were studied. It was found that for the sample synthesized by spray-drying using OTAB as a template both sorption and desorption rate of Dy³⁺ ions is high, due to the defined porosity of the sorbent. Sorption of Dy³⁺ ions by bridged silsesquioxane xerogels with disordered structure is significantly hindered by diffusion processes, due to the chaotic packing of globules. Using a model for the chemical reactions, the composition of dysprosium(III) complexes with surface phosphonic groups were determined, and their formation constants were calculated. It was shown that xerogels with higher surface concentration of ligand groups (L), can form complexes DyL₃ and DyL₄ ^?. Meanwhile, the sample synthesized by spray-drying method forms only DyL₂ ⁺ and DyL₃ complexes. For this sample, complexes DyL₃ are more stable than for xerogels. So, mesoporous silica derived by spray-drying method, with defined spatial porosity and relatively low surface concentration complexation groups, is characterized by the best sorption properties towards dysprosium(III) (adsorption and desorption kinetics, the value of the static sorption capacity).     

Removal of Dichromate Anions with Nanofiltration‐Complexation by using Amino Calix[4]arene Derivative

Abstract

Herein the removal and recovery of chromium anions from aqueous solutions by using nanofiltration pilot‐scale equipment (Osmonics Sepa CF Membrane Cell) with a water‐soluble amino calix[4]arene derivative was studied. To understand the selectivity, the authors also examined the retention of chromium anions in the presence of Cl^?, NO₃ ^?, SO₄ ^2?, HSO₄ ^?, CO₃ ^2?, PO₄ ^3?, H₂PO₄ ^? anions in nanofiltration‐complexation. From the results water‐soluble amino calix[4]arene was effective and selective ligand for dichromate anions over nitrate anions, in a nanofiltration‐complexation system at pH 2.5. Moreover, the recovery and reusability studies of dichromate and nitrate anions and also ligand were performed.     

Solid polymer electrolytes VIII: effect of LiClO4-doped level on the microstructure and ionic conductivity of a chemical-covalently polyether-siloxane hybrid electrolyte

A new hybrid polymer electrolyte system based on chemical-covalently polyether and siloxane phases is designed and prepared in the presence of lithium perchlorate (LiClO₄) which acted as both ionic source and the epoxide ring-opening catalyst. The effect of salt-doped level on the microstructure and ionic conductivity of these composite electrolytes were investigated by means of Fourier transform infra-red spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis, a.c. impedance and multinuclear solid-state nuclear magnetic resonance measurements. DSC results indicate that the formation of transient cross-links between Li⁺ ions and the ether oxygens on complexation with LiClO₄ results in an increase in polyether segment T_g. However, the polyether segment T_g decreases at the highest salt concentration (5.0 mmol LiClO₄/g PEGDE), ascribing to the plasticizing effect. The behavior of ion transport is coupled with the segmental motions of polymer chains and also correlated with the interactions between ions and polymer host.     

Chelating ability of a conjugated redox active tetrathiafulvalenyl-acetylacetonate ligand

A novel tetrathiafulvalene (TTF) bearing a conjugated β-diketone moiety (TTFacacH) has been synthesized and fully characterized. The chelating ability of its enolate anion (TTFacac) has been investigated with [M^II(OAc)₂ · xH₂O] (OAc = acetate and M = Zn, Cu and Ni) leading to complexes, where the metal center is coordinated by two TTFacac. Modulation of the redox properties of the TTF can be achieved through the simple change of the two apical ligands which completed the octahedral coordination geometry. This redox active ligand shows promising features for the elaboration of hybrid organic–inorganic building blocks.     

Enantiomeric Separation of Tryptophan by Ultrafiltration Using the BSA Solution System

Abstract

The optical resolution of racemic tryptophan was performed by ultrafiltration using the BSA solution system. The pH of the feed solution had a strong influence on the complexation constants between BSA and tryptophan, especially for L-tryptophan. The complexation constant for L-tryptophan reached a maximum value at pH 9 (K _L = 110,000), varying by 2 orders of magnitude in the range from pH 6 (K _L = 1000) to pH 11 (K _L = 21,000). Smaller variations of the complexation constant of D-tryptophan were observed. Based on these data, the recovery and the purity of the permeate were optimized by a proper control of the physicochemical parameters of the feed solution (essentially pH and initial concentrations). In one stage, 91% purity with a 89% recovery of D-tryptophan has been easily obtained with a high permeation rate (6.3 × 10^?4 mol·m^?2s^?1 at 1.5 bar).     

Synthesis and binding properties of polymeric calix[4]arene nitriles

Two new polymers containing pendant calix[4]arene units with nitrile functionalities at their lower rim have been synthesized via radical initiated reactions involving a vinylic monomer 6 {5,11,17,23-tetra-tert-butyl-25,26,27-tris(cyanomethoxy)-28-(2-acryloyloxy) ethoxycalix[4]arene} and with styrene. A five atom spacer group was incorporated between the bulky calixarene core and the acrylate moiety in order to minimize steric interactions which proved to impede the polymerization. The complexation studies were made by using liquid–liquid extraction procedures. It has been deduced from the observations that both polymers show a good selectivity towards Hg²⁺ like their precursor 5,11,17,23-tetra-tert-butyl-25,26,27-tricyanomethoxy-28-(2-hydroxy)ethoxycalix[4]arene 5, which supports their utility as adsorbents or potential candidate materials for fabricating membranes and sensors, which can separate or detect Hg²⁺ metal ions in a high selectivity.     

Microemulsion synthesis of ms/tz-BiVO4 composites: The effect of pH on crystal structure and photocatalytic performance

In this work, BiVO₄ composites, containing the tetragonal zircon phase (tz-BiVO₄), and monoclinic scheelite phase (ms-BiVO₄), were synthesized using the microemulsion method. The effect of pH on phase composition and photocatalytic activity were investigated. Based on X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), a ms/tz-BiVO₄ composite forms at pH = 1.0 and pure ms-BiVO₄ is obtained in the pH range 4.0–10.0. The three primary steps in preparing BiVO₄ were monitored by optical microscopy and the role played by the microemulsion on the phase composition of BiVO₄ is explained. Photoluminescence spectroscopy (PL), UV–visible diffuse reflectance spectroscopy (UV-DRS), Brunauer-Emmett-Teller (BET), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) were employed to characterize the physical and chemical properties of BiVO₄ composites. The composite formed at pH = 1 exhibited the lowest hole-electron (h⁺-e^-) recombination rate, resulting in the highest photocatalytic activity towards microcystin-LR (MC-LR), with near 100% removal of MC-LR in 5 h. ESR and trapping experiments indicated that MC-LR degradation was mediated primarily by hydroxyl radicals (•OH), superoxide radicals (O₂^•−) and photogenerated holes (h⁺).     

Azo-hydrazone tautomerism by in situ Cu ion catalysis and complexation with the H2O2 oxidant of C.I. Disperse Yellow 79

A novel dinuclear copper(II) complex 2 bearing double μ₂-oxo bridges has been obtained by in situ Cu^II ion catalysis and complexation with the H₂O₂ oxidant of C.I. Disperse Yellow 79 (1), where a new dianionic ligand is in situ formed having an additional phenolic group and it coordinates with the central Cu^II ion as a tridentate chelating ligand. Furthermore, both of the starting material 1 and the final neutral dye-metal product 2 have been structurally and spectrally characterized and compared, where azo-hydrazone tautomerism has been observed before and after metal-ion complexation. To the best of our knowledge, this is the first structural report about the heterocyclic dyes having quinoline-2,4-dione skeleton and the corresponding azo-hydrazone tautomerism between them.     

A sodium boroxide containing an unusual Na4O4 ladder core

The reaction of dimesitylborinic acid and sodium tert-butoxide in toluene afforded the partially deprotonated boroxide salt, [Na₄(OB{mes}₂)₄(HOB{mes}₂)₂], which crystallized from hexane with a laddered Na₄O₄ motif containing a neutral, disubstituted borinic acid ligand.     

Oxygen reduction at negatively charged iron porphyrins heat-treated and bridged by alkaline-earth metal ions

An ordered network of tetrasodium tetra(4-sulphonatophenyl)porphyrin iron(III) chloride (FeTPPS₄Na₄), which exhibited a higher catalytic activity for oxygen reduction than Co and Ir(CO)TPPS₄Na₄, was fabricated by complexation with alkaline-earth metal ions. Heat treatment of these complexes enhanced their catalytic activity with the highest performance observed with Ba²⁺-FeTPPS₄. The onset potential for oxygen reduction (E_onset) was 720 mV vs. Ag|AgCl, which is almost the same as that for Pt-impregnated carbon black. The number of electrons, n, transferred during oxygen reduction at a Ba²⁺-FeTPPS₄-coated electrode, as determined by rotating ring-disc experiments, was 3.9 and suggests that oxygen was reduced to water. A neutral solution of FeTPPS₄Na₄ was acidified by the addition of barium ion, and the elemental ratio Fe:S:Ba in the resulting Ba²⁺-FeTPPS₄ complex was approximately 1:4:2.5. This suggests the formation of a highly ordered network with Fe sites bridged with barium ions in addition to the normal salt bridges between sulphonates. Catalytic oxidation reactions with nitric oxide and nitrite ion as the intermediate at the heat-treated Ba²⁺-FeTPPS₄ indicate the formation of Fe(IV) and Fe(IV) π-cation radicals or Fe(V). The agreement between the potential of Fe(IV) π-cation radical formation and E_onset suggests that the redox cycle of the Fe(III)/Fe(IV) π-cation radical provides a sufficient driving force for the observed 4-electron reduction of oxygen at the heat-treated Ba²⁺-FeTPPS₄ electrode.     

Vanadium(V)-catalyzed epimerization of isoleucine

All stereoisomers of isoleucine were transformed to the mixtures of the corresponding epimers by epimerization in alkaline aqueous solution. The catalyst was formed in situ by condensation of salicylaldehyde and isoleucine followed by complexation with vanadate. No derivatization of the amino acid was necessary. The tetrabutylammonium salts of [VO₂(N-salicylidene-isoleucinato)]⁻ can be used for diastereomeric separation of the epimers providing low yields and moderate diastereoselectivities.