Cationic cobaltammine as anion receptor: Synthesis, characterization, single crystal X-ray structure and packing analysis of hexaamminecobalt(III) chloride (R,R)-tartrate monohydrate

In an effort to utilize the [Co(NH₃)₆]³⁺ cation as a new anion receptor (binding agent) for dihydroxy dicarboxylate anion i.e., tartrate, orange single crystals of hexaamminecobalt(III) chloride (R,R)-tartrate monohydrate, [Co(NH₃)₆]Cl(C₄H₄O₆)·H₂O, were obtained by reacting hexaamminecobalt(III) chloride with potassium–sodium tartrate tetrahydrate in a 1:1 molar ratio in hot water. The single crystal X-ray structure determination of [Co(NH₃)₆]Cl(C₄H₄O₆)·H₂O revealed that a distinctive network of hydrogen bonding interactions (N–HO, N–HCl⁻, O–HO) stabilize the crystal lattice. This is the first complex salt of hexaamminecobalt(III) with dihydroxy dicarboxylate anion i.e., tartrate.     

四(4-三甲胺苯基)卟啉-镉络合物的极谱吸附波

本文研究了镉-四(4-三甲胺苯基)卟啉络合物在氢氧化钠溶液中的极谱吸附波。采用本方法测定了电镀废水、自来水及铝合金中微量镉。对该吸附波的产生机理作了初步探讨,并运用极谱摩尔比法测定了络合物的组成和条件稳定常数。     

Phencyclone Diels-Alder adducts as a new crystalline host. Role of C---H···π and C---H···O interactions

A series of crystalline host compounds, which have a bicyclo[2.2.1]heptene-7-one system, has been synthesized and their inclusion behavior has been investigated. The cycloadduct of phencyclone and N-naphthylmaleimide forms a 1:1 crystalline inclusion complex with 2-butanone. The crystal structure indicates the presence of weak lattice forces supported by C---H···π and C---H···O interactions.     

Determination of divalent trace metals in natural waters by preconcentration on N,N,N′,N′-tetra(2-aminoethyl)ethylenediamine-silica followed by on-line ion chromatography

A method for the on-line preconcentration and chromatography of trace metals, e.g., Co, Ni, Cu, Zn, Cd and Pb, on N,N,N′,N′-tetra(2-aminoethyl)ethylenediamine-bonded silica is described. The preconcentrated metals were desorbed with 0.13 M tartrate, which allows direct separation on a cation-exchange chromatographic column. The metals separated were detected by postcolumn reaction with 4-(2-pyridylazo)resorcinol and measuring the absorbances at 500 nm. Linear calibration graphs were obtained over the range 1 · 10⁻⁸−3 · 10⁻⁶ M. The synthesis and characteristics of the chelated silica are described. The method was applied to the analysis of river and interstitial sediment waters.     

The Spectrophotometric Determination of Gallium (III) with Glycine Thymol Blue

The reaction between gallium (III) and glycine thymol blue has been studied spectrophoptometrically in order to establish the optimum conditions for determining traces of gallium. The gallium (III) glycine thymol blue complex has an absorption maximum at 560 nm against a reagent blank and is stable between pH 4.0 and 5.5. The complex has a composition 1 : 2 and a formation constant of 6.4×10⁷ under the conditions studied. Beer's law is obeyed upto 126 μg of gallium. The net molar absorptivity has been found to be 11,000. The present method is very sensitive and rapid. Anions such as citrate and tartrate inhibit the colour development of the complex.     

H NMR Spectra and electronic structure of binuclear niobocene and titanocene containing fulvalene ligands

¹H NMR spectra of binuclear metallocene hydride complexes, (η⁵ : η⁵-C₁₀H₈)(C₅H₅)₂M₂(μ-H)₂ (M = Nb, 20°C and Ti, (−60 to +25°C), were studied. The Nb complex is diamagnetic and gives a high resolution spectrum. The coordination of bridging hydride H atoms provides Nb atoms with complete 18 electron configuration. In its ground state, the Ti complex is also diamagnetic (the spectrum at −60°C agrees to that) in spite of only 17 electron configuration of each Ti atom. However, the population of the excited triplet state in the case of the Ti complex is appreciable at temperatures higher than −30°C, the proton resonance lines being shifted downfield and significantly broadened as compared with the spectrum at −60°C.     

Hydrophobic and metal coordination interacted architecture based on p-tert-butylthiacalix[4]arene–potassium complex and its vapor absorption capability

Single-crystal X-ray diffraction studies of [K(1·3H)]·2MeOH complex obtained from p-tert-butylthiacalix[4]arene (1·4H) with KH, which shows two dimer formations. One of the dimers is formed by a hydrophobic interaction between each tert-butyl group of 1·3H and the cavity of another 1·3H in the crystalline state. The other dimer made metal coordination SK(O,S,O) between neighboring 1·3H and potassium ion. In the overall structure, this complex indicates non-porous structure and the adsorption capabilities toward gaseous organic molecules.     

The binding energy of Ni·N2O

The electrostatic complex of Ni⁺ with a single nitrous oxide molecule, Ni⁺·N₂O, has been studied by resonant photodissociation spectroscopy. Optical absorptions are detected via predissociation of the ion into Ni⁺ and N₂O fragments. A cutoff in the resonant photofragmentation is observed below 17230 cm⁻¹ which represents the threshold for the lowest quartet dissociation pathway. This places the binding energy of the Ni⁺·N₂O complex at 1.096±0.003 eV. The binding energy of this complex is only slightly greater (≈ 16 meV) than that of the similar compound, Ni⁺·CO₂. Speculation is presented supporting a T-shaped ground state geometry in both species.     

Sensitive spectrophotometric determination of beryllium with Eriochrome Cyanine R and cetyltrimethylammonium ions

In the presence of cetyltrimethylammonium ions (CTA) a significant bathochromic shift in the color reaction of beryllium with Eriochrome Cyanine R (ER) takes place. This is accompanied by a nearly trifold increase in the sensitivity. The triple complex of beryllium with Eriochrome Cyanine R and CTA (in which the molar ratio of Be:ER is 1:2) is proposed as a basis of a new sensitive spectrophotometric method of beryllium determination. The molar absorptivity ? = 8.65 × 10⁴ at λ_max = 590 nm, pH ~ 7 (borate buffer), when the solution is heated at 60 °C for 15 min. The method is very selective when EDTA is used as a masking agent. EDTA does not affect the formation of the triple beryllium complex neither do tartrate, citrate, and acetate. Phosphate and fluoride interfere.     

Spectrophotometric methods for the determination of osmium-III Reaction of osmium tetroxide with 1:5-diphenylcarbo- hydrazide in aqueous solutions followed by extraction of the complex

-A spectrophotometric method has been developed which is applicable to the determination of extremely small quantities of osmium. Osmium is oxidised to the octovalent state, then added to an acidic aqueous solution containing 1:5-diphenylcarbohydrazide (DPC). After heating the aqueous solution to 65°, the osmium-DPC complex is extracted with chloroform. A molar absorbancy index of about 150,000 is obtained. From 7 to 25 μg of osmium can be determined with a coefficient of variation of 6%. It was established that Fe^III, Cu^II, Ru^III and Au^III seriously interfere in the determination of osmium by this method, while Cr^VI, Ni^II, Mo^VI, Ir^III and chloride interfere only when present in relatively high concentrations.     

Determination of absorptivity and formation constant of a chalcone association complex

A UV spectrometric method was developed to determine the molar absorptivity (_C) and formation constant (K_c) of the association complex of unsubstituted chalcone in cyclohexane, in the concentration range from 4.00·10⁻⁴ to 2.00·10⁻² mol dm⁻³. The thermodynamic and spectroscopic magnitudes such as K_c and _C contribute to the understanding of the physicochemical behavior of several ,β-unsaturated carbonylic compounds, of low solubility in water, as it is the case of numerous flavonoids of chemical and biological importance. The studied association complex, formed by two chalcone molecules, is characterized by the constants _C (300.8 nm)=4.98·10⁴ dm³ mol⁻¹ cm⁻¹ and K_c=5.58·10³. The method proposed is convenient for the study of solute–solute molecular associations particularly those due to dipole–dipole interactions.     

Syntheses and structural characterization of transition metal(II) coordination polymers containing 4,4′-dipyridyldisulfide

The reactions of Zn(NO₃)₂ · 6H₂O and FeSO₄ · 7H₂O with 4-PDS (4-PDS = 4,4′-dipyridyldisulfide) and NH₄SCN in CH₃OH afforded the complexes [Zn(NCS)₂(4-PDS)]_n (1) and [Fe(NCS)₂(4-PDS)₂ · 4H₂O]_n (2), respectively, while the reaction of CoCl₂ · 6H₂O with 4-PDS in CH₃OH gave the complex {[Co(4-PDS)₂][Cl]₂ · 2CH₃OH}_n, (3). These complexes have been characterized by spectroscopic methods and their structures determined by X-ray crystallography. The 4-PDS ligands in 1 are coordinated to the metal centers through the nitrogen atoms to form 1-D zigzag-chains, and the distorted tetrahedral coordination geometry at each zinc center is completed by a pair of N-bonded thiocyanate ligands. Compound 2 has a 1-D channel-chain structure and each octahedral Fe(II) metal center is coordinated by four 4-PDS ligands and two trans N-bonded thiocyanate ligands. Weak SS interactions in complex 1 link the 1-D chains into 2-D molecular sheets. In complex 2, the channel chains are interlinked through SS interactions to form molecular sheets, which interpenetrate through the SS interactions to form 3-D structures with large cavities that are occupied by the water molecules. Compound 3 also has a 1-D channel-chain structure with each square-planar Co(II) metal center coordinated by four 4-PDS ligands. Multiple C–HCl hydrogen bonds and SO interactions in 3 link the 1-D chains into 2-D structures.     

A kinetic study of C- and O-alkylation of some cyclic β-keto esters

The reactions of sodio-2-carbethoxycyclanones of 5, 6 and 8 ring members (I-5, I-6, I-8) with isopropyl iodide in dimethylsulfoxide (DMSO) have been studied kinetically at three temps. Three competing second order reactions occur: isopropylation at carbon, isopropylation at oxygen and propene formation. The total rate constants were dissected into individual rate constants by an independent measurement of propene formation and by GLC of the alkylation product mixtures. At 30°, the C/O ratios for I-5, I-6 and I-8 are 1·74, 1·34 and 7·72 respectively. Increasing temps favor O-alkylation in all cases since it has the higher enthalpy of activation of the two alkylation processes. Relative rates of C-alkylation at 30° for I-5:I-6:I-8 are 1·7:1:4·4 whereas for O-alkylation the relative rates are 1·3:1:0·8. The insensitivity of the O-alkylation process to structural change in the anion and the anomalous position of I-8 in the reaction series for O-alkylation are attributed to a coincidence of the experimental temperature and the isokinetic temp.     

Spectrophotometric study and analytical application of the reaction between manganese(II) and 4-(2-pyridylazo)resorcinol

A highly sensitive method for spectrophotometric determination of manganese(II) with 4-(2-pyridylazo)resorcinol (PAR) as reagent is described. The molar absorptivity of the complex was found to be 8.65 ± 0·04 x 10⁴. The stability constant of the ML₂ complex was found to be log β₂ = 15·6. Beer's law is obeyed within the range 0·02–0·5 μg of Mn/ml. An application of this reaction for analytical purposes is described.     

New mono and binuclear mercury(II) complexes of phosphorus ylides containing DMSO as ligand: Spectral and structural characterization

Reaction of phosphorus ylides Ph₃PCHC(O)C₆H₄NO₂ (Y′) and (p-tolyl)₃PCHC(O)C₆H₄Cl (Y″) with HgX₂ (X = Cl, Br and I) in equimolar ratios using methanol as solvent leads to binuclear products. The bridge-splitting reaction of binuclear complex [(Y″) · HgI₂]₂ by DMSO yields the mononuclear complex [(Y″) · HgI₂ · DMSO]. This bridge-splitting reaction can be also a method for the synthesis of mononuclear products. C-coordination of ylides and O-coordination of DMSO are demonstrated by single crystal X-ray analyses of binuclear complexes of [(Y′) · HgI₂]₂ and [(Y″) · HgI₂]₂ and mononuclear complex of [(Y″) · HgI₂ · DMSO]. Characterization of the obtained compounds was also performed by elemental analysis, IR, ¹H, ³¹P, and ¹³C NMR. Theoretical studies on Hg(II) complexes of Y′ show that the cis-like isomers are about 4–12 kcal/mol less stable than the trans-like structures and the relative energy of cis- and trans-like isomers significantly depends on the size of the bridging halide. These studies on mercury complexes of Y″ show that, formation of mononuclear complexes in DMSO solution in which DMSO acts as a ligand, energetically is more favorable than that of binuclear complexes.     

Location of the discotic lamellar-nematic tricritical point and isotope effects in the caesium pentadecafluorooctanoate (CsPFO)/water system as established by 133 Cs N.M.R. spectroscopy

¹³³Cs N.M.R. spectroscopy has been used to locate the discotic lamellar (smectic A)-nematic tricritical point in the CsPFO/H₂O and CsPFO/²H₂O systems. In both systems this occurs at the same volume fraction of 0·25, but at different temperatures (302·05 and 304·80 K, respectively). The phase diagram for the CsPFO/H₂O system has also been studied for the first time and a comparison of the corresponding fixed points shows there to be large isotope effects.     

The structure of 2,4-dibromomenthone

A three-dimensional X-ray diffraction study has shown that the product obtained by bromination of - or -menthone is 2,4-dibromomenthone [2(a), 6(e)-dibromo-2(e)-isopropyl-5(e)methyl cyclohexanone]. The two Br atoms are trans, and the isopropyl and methyl groups are also trans. There are four molecules in the unit cell, which has symmetry P2₁2₁2₁ and dimensions a = 13·58, b = 13·81 and c = 6·25 Å. One intermolecular Br … Br contact of 3·52 ± 0·01 Å occurs, a distance which is about 0·4 Å shorter than the van der Waals distance.     

Thermal study of palladium complexes with trans-1,2-diaminecy clohexanetetraacetic acid

Thermal decomposition processes for cyclohexanediaminetetraacetic acid (CDTA-H₄) complexes of palladium, [Pd(CDTA-H₂)] and [Pd(CDTA-H₄)Cl₂]·2 HCl·2 H₂O have been studied using TG—DTA techniques. Infrared spectroscopy and X-ray diffraction have been also used for the characterization of intermediate and final products. In the decomposition of the dichloro complex, chloride ions are released simultaneously to a ring closure reaction in which CDTA becomes tetradentate. For both compounds, the final product in the decomposition is PdO, as confirmed by the X-ray difraction pattern of a sample heated at 600°C.     

The analysis of beryllium and beryllium oxide—IV The determination of cobalt

A method is described for the determination of cobalt in beryllium or beryllium oxide by extraction of the cobalt thiocyanate complex with acetylacetone (2:4-pentanedione). The method is accurate to ±2% or 2 μg of cobalt, whichever is greater. Of the 68 elements investigated only manganese and chromium interfere in 10 mg amounts. No interference was observed when 1g of each had been removed by ion-exchange or volatilisation (of chromium only) before extraction.     

Synthesis and Enantioselective Discrimination of Chiral Fluorescence Receptors Bearing Amino Acid Units

Two chiral fluorescence receptors （1, 2） were synthesized, and their structures were characterized by IR, ^1H NMR, ^13C NMR, mass spectra and elemental analysis. The chiral recognition of receptors was studied by ^1H NMR and fluorescence spectra. The results demonstrate that receptors and dibenzoyl tartrate anion formed a 1 ： 1 complex. The receptor 1 exhibited a good enantioselective recognition ability toward the enantiomers of dibenzoyl tartrate anion.