Stability and Structure of Silver–l-methionine Complexes

Journal of Solution Chemistry - Stability and structure of complexes between silver (I) and l-methionine (L) deduced from potentiometric and 1H NMR measurements allow to assume the prevailing of...     

Synthesis of Glass-Ceramics in Mixed Fluorozirconate–Phosphate Systems

Fluorozirconate-phosphate glasses of the ZrF₄–BaF₂–NaPO₃(LiPO₃) and ZrF₄–BaF₂–LaF₃–AlF₃–LiPO₃ systems doped with EuF₃, ErF₃, and NdF₃ were studied by the differential-thermal (DTA) and X-ray diffraction (XRD) analysis, luminescence spectroscopy, scanning and transmission electron microscopy (SEM and TEM) methods. Addition of the phosphate component up to 20 mol % decreases the glass transition temperature and increases the glass stability to crystallization. Heat treatment in the range >T_g–T_c1 of glass transition and first maxima of crystallization temperatures causes crystallization of nanosized β-BaZrF₆ particles. At LiPO₃ (NaPO₃) concentrations of more than 80 mol %, glasses containing a crystalline phase are formed during the synthesis process.

     

Design, Synthesis of Chiral Ketone and Application in Asymmetric Epoxidation

A class of chiral ketone was synthesized for asymmetric epoxidation. High ee values have been obtained for a number of cis olefin and trans olefin. The epoxidation was stereospecific with no isomerizatiom observed in the epoxidation of acyclic system. Encourageingly high ee value has also been obtained for a number of terminal olefins. Mechanistic studies show that electronic interactions play an important role in the stereodifferentiation. O O O O O O NBoc O O t-BuO2CH2CN O O O …     

Synthesis and Characterization of Silver–Platinum Bimetallic Nanowires and Platinum Nanotubes

A galvanic replacement reaction was used to prepare silver–platinum bimetallic nanowires and platinum nanotubes. Silver nanowires, prepared by boiling aqueous silver nitrate with sodium citrate in the presence of small amount of sodium hydroxide, were used as the sacrificial template in the galvanic reaction to prepare silver–platinum bimetallic nanowires and ultimately hollow platinum nanotubes. The resulting nanomaterials are stable and can be isolated without core aggregation or decomposition. These new materials have been characterized by transmission electron microscopy, energy dispersive X-ray analysis, and inductively coupled plasma atomic emission spectroscopy.     

Synthesis and Structure of Complexes Formed in the CuCl2–Cu–N-allylquinolinium Chloride System

The crystals of [C₉H₇N(C₃H₅)]₂Cu^IICl₄(IV) were obtained through ac electrochemical synthesis using CuCl₂· 2H₂O, N-allylquinolinium chloride, and copper electrodes in an ethanol-benzene medium. These crystals transformed with time into crystals of the [C₉H₇N(C₃H₅)][Cu^IICl₃(C₉H₇N)] complex (V). When tin(II) chloride was added to the initial reagents, the [C₉H₇N(C₃H₅)]Cu^I ₂Cl₃complex (VI) was obtained. The X-ray diffraction analysis (DARCh-1 autodiffractometer, MoK radiation, Zr filter) indicated that complexes IVand Vcrystallize in the triclinic system: space group P ; for IV, a= 12.817(4), b= 10.435(3), c= 9.606(3) Å, = 97.94(2)°, = 107.28(2)°, = 95.99(2)°, V= 1200.6(6) ų, Z= 2; for V, a= 16.992(5), b= 8.243(2), c= 7.345(3) Å, = 91.89(3)°, = 91.19(3)°, = 88.18(3)°, V= 1027.5(6) ų, Z= 2. Crystals VIare monoclinic, space group P2₁/n, a= 13.578(5), b= 15.079(4), c= 6.953(4) Å, = 105.08(4)°, V= 1370.6(10) ų, Z= 4. Structures IV–VIconsist of N-allylquinolinium cations and different anions: isolated [CuCl₄]^2–tetrahedrons (IV), [C₉H₇NCuCl₃]^–tetrahedrons (V) containing a quinoline molecule, and a polymer chain |[Cu^I ₄Cl₆]^2–} _n (VI) in which two independent metal atoms have trigonal-pyramidal and planar-trigonal environments. The C=C bond of the allyl group is not involved in cooordination with the Cu(I) atom.     

Synthesis and Characterization of Silver–PVA Nanocomposite for Sensor and Antibacterial Applications

Silver–polyvinyl alcohol (PVA) nanocomposite is synthesized by a simple chemical reduction method in aqueous media and characterized by various techniques such as UV–Visible spectroscopy, transmission electron microscopy, X-ray diffraction and infrared spectroscopy. The morphology of the obtained silver nanoparticles is spherical in shape with an average diameter of 24 nm. The prepared silver–PVA nanocomposite is demonstrated to detect the concentration of heavy metal contaminant cadmium in water based on linear change in surface plasmon resonance absorption strength. The antibacterial tests show the inhibiting action of this nanocomposite against pathogenic bacteria Escherichia coli and Pseudomonas aeruginosa (gram negative), Bacillus cereus and Staphylococcus aureus (gram positive), which are found commonly in water. These observed optical and antibacterial properties, suggest the possible utilization of prepared silver–PVA nanocomposite in the water purification application.     

Synthesis and Characterization of Lewis Base Stabilized Gallium–Tellurium Complexes

Abstract

Complexes of gallium bound to chalcogen elements recently have found importance in synthesis and as single molecular precursors for preparing thin films of gallium chalcogenides for their applications as photo-receivers for visible and near IR region. Herein we report the synthesis and characterization of some Lewis base (LB) stabilized gallium-telluride complexes. Gallium tellurolate complexes of formula, [LB] · [Ga(TePh)₃] _x , [x = 1, LB = 4-dimethylaminopyridine; x = 2, LB = 4,4′-methylene bis(N,N′-dimethylaniline] were prepared by reacting the corresponding Lewis base adduct of gallium(III) iodide and phenyllithium tellurolate. The complexes have been characterized by elemental analyses, ICP-MS, multinuclear NMR, and thermal and mass spectrometry. Such complexes may be potential single-molecular precursors for III–VI electronic materials.     

Effect of the Composition of Ethanol–DMSO Solvents on the Stability of Silver(I) Complexes with 18-Crown-6

The effect of composition of ethanol–dimethyl sulfoxide (EtOH–DMSO) solvents (χ_DMSO = 0.0–1.0 mole fractions) on the stability of silver(I) complexes with 18-crown-6 ether (18C6) has been studied potentiometrically at 298.15 K. The increasing of DMSO concentrations in mixed solvents are shown to considerably reduce the stability of 18C6 complexes with silver(I) ion ([Ag18C6]⁺). A change in the solvation state of the central ion is suggested to be the key factor in shifting complexing equilibrium.     

Synthesis and Structure of New Cobalt–Carbonyl Complexes Containing Tellurium Atoms

Co₂(CO)₈ and Te₂O react to form the well known Co₄(CO)₁₀Te₂, Co₄(CO)₁₁Te₂ complexes and the two new cluster complexes CCo₆(CO)₁₂Te₂(1), and CCo₆(CO)₁₀Te₂(Te₃) (2). The structures of 1 and 2 were determined by X-ray analysis, together with the triphenylphosphine derivative of 1, CCo₆(CO)₁₁(PPh₃)Te₂(3), which was analyzed to clarify the disordered structure of the parent compound. Complex 1 is formed by a prismatic cluster of cobalt atoms with a carbon embedded in the cage; two tellurium atoms cap the triangular faces of the prism and each cobalt atom links two terminal carbonyl groups. The complex 2 has a similar prismatic cage CCo₆; two ₄-Te atoms cap two rectangular faces of the prism, while other two Te atoms bridge two edges of the triangular faces and are linked each other through a third Te atom. Electron counting gives for complex 2 92 electrons: the presence of two long Co–Co distances suggests that the two excess electrons are located on Co–Co antibonding orbitals. Crystal data for 1, space group C2/c, a = 12.845(2) Å, b = 13.449(2) Å, c = 13.246(2) Å, = 91.95(2)°, Z = 4, R = 0.097 for 2555 reflections; for 2, space group Pnna, a = 17.219(5) Å, b= 14.969(6) Å, c = 9.178(4) Å, Z = 4,R = 0.037 for 3103 reflections; for 3, space group P2₁/c, a = 9.288(2) Å, b = 14.920(6) Å, c = 26.300(9) Å, = 99.99(2)°, Z = 4, R = 0.037 for 4300 reflections. The vibrational analysis of the complex 1 was performed and most of the (CO), (₆C–Co), (Co–Co) and (Co–Co) modes were assigned. The (Co–Te) modes were interpreted on the basis of the intermolecular coupling, due to the close contact between neighboring clusters in one distinct direction in the crystal.     

Synthesis,Structure and Reactivity of Lanthanocene Complexes

ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｃｈｅｍｉｓｔｒｙｏｆｏｒｇａｎｏｌａｎｔｈａｎｉｄｅｓｈａｓｅｘｐｅｒｉｅｎｃｅｄｅｘｔｒｅｍｅｌｙｉｍｐｏｒｔａｎｔｄｅｖｅｌｏｐｍｅｎｔｓｄｕｒｉｎｇｔｈｅｌａｓｔｔｗｏｄｅｃａｄｅｓ ,ａｎｄｎｕｍｅｒｏｕｓｕｎｕｓｕａｌｃｏｍｐｏｕｎｄｓｗｉｔｈｕｎｐｒｅｃｅ ｄｅｎｔｅｄｓｔｒｕｃｔｕｒｅｓａｎｄｕｎｉｑｕｅｒｅａｃｔｉｖｉｔｙｐａｔｔｅｒｎｓｈａｖｅｂｅｅｎｐｒｅｐａｒｅｄ .1ＯｒｇａｎｏｌａｎｔｈａｎｉｄｅｃｏｍｐｏｕｎｄｓｃｏｎｔａｉｎｉｎｇＬｎ—Ｃ ,…     

Conductance and Thermodynamic Study of Thallium and Silver Ion Complexes with Crown Ethers in Different Binary Acetonitrile–Water Solvent Mixtures

The complexation reactions between Ag⁺ andTl⁺ ions with 15-crown-5 (15C5) and phenyl-aza-15-crown-5(PhA15C5) have been studied conductometrically in 90%acetonitrile-water and 50% acetonitrile - water mixed solvents attemperatures of 293, 298, 303 and 308 K. The stability constants of theresulting 1 : 1 complexes were determined, indicating that theTl⁺ complexes are more stable than the Ag⁺complexes. The enthalpy and entropy of crown complexation reactions were determined from the temperature dependence of the complexation constants.The enthalpy and entropy changes depend on solvent composition and the T S⁰ _o–H⁰ plotshows a good linear correlation, indicating the existence of entropy –enthalpy compensation in the crown complexation reactions.     

Synthesis,Crystal Structure and Electrochemistry Property of 5,5'-dimethyl-2,2'-bipyridine Silver(Ⅰ) Complexes

The synthesis, crystal structures and electrochemistry of two easily soluble silver(Ⅰ) complexes[Ag(dmbpy)(NO₃)] 1 and[Ag(dmbpy)](ClO₄) 2,where dmbpy is 5,5'-dimethyl-2,2'-bipyridine, have been studied. Single-crystal X-ray diffraction reveals each silver(Ⅰ) atom in 1 is in a Y-shape coordination geometry with (the average Ag-N=2.278 Å) two N atoms from a dmbpy and an O atom (AgO=2.218 Å) from the monodentate nitrate. Each silver(Ⅰ) atom in 2 is three-coordinated by three N atoms, two of which are from a dmbpy, and one from the acetonitrile. 1 and 2 underwent an overall cyclic voltammogram process in acetonitrile and both complexes are stabilized by dmbpy in acetonitrile.     

Continuous Flow Synthesis of Metal–NHC Complexes**

The use of weak bases and mild conditions is currently the most sustainable and attractive synthetic approach for the preparation of late-transition metal complexes, some of which are widely used in catalysis, medicinal chemistry and materials science. Herein, the use of cuprate, aurate or palladate species for a continuous flow preparation of Cu^I, Au^I and Pd^II-NHC complexes is reported. All reactions examined proceed under extremely mild conditions and make use of technical grade acetone as solvent. The scalability of the process was exemplified in a multigram-scale synthesis of [Cu(IPr)Cl].     

Synthesis,Structure, and Haptotropic Interconversions of Tungsten Cycloheptatrienyl–Acetonitrile–Carbonyl Complexes

Russian Journal of Coordination Chemistry - Tungsten cycloheptatrienyl complexes (η7-C7H7)W(CO)2I (I), [(η3-C7H7)W(CO)2(CH3CN)3]PF6 (II), and [(η7-C7H7)W(CO)2(CH3CN)]PF6 (III) (CIF...     

Synthesis,Structure, and Bonding of d3 Molybdenum–Oxo Complexes

Reduction of d² metal–oxo ions of the form [MO(PP)₂Cl]⁺ (M=Mo, W; PP=chelating diphosphine) produces d³ MO(PP)₂Cl complexes, which include the first isolated examples in group 6. The stability and reactivity of the MO(PP)₂Cl compounds are found to depend upon the steric bulk of the phosphine ligands: derivatives with bulky phosphines that shield the oxo ligand are stable enough to be isolated, whereas those with phosphines that leave the oxo ligand exposed are more reactive and observed transiently. Magnetic measurements and DFT calculations on MoO(dppe)₂Cl indicate the d³ compounds are low spin with a ²[(d_xy)²(π*(MoO))¹] configuration. X-ray crystallographic and vibrational-spectroscopic studies on d² and d³ [MoO(dppe)₂Cl]^0/+ establish that the d³ compound possesses a reduced M−O bond order and significantly longer Mo−O bond, accounting for its greater reactivity. These results indicate that the oxo-centered reactivity of d³ complexes may be controlled through ligand variation.     

Facile Synthesis of Luminescent Ir–Pt–Ir Trimetallic Complexes

A new class of luminescent, heterotrimetallic supramolecular constructs partnering two bis-cyclometalated iridium centers with a diimine platinum acetylide center is introduced. Whereas most supramolecular constructs featuring cyclometalated iridium involve elaborate bridging ligands and are prepared under forcing conditions with low to moderate yields, the three Ir–Pt–Ir complexes described here are prepared at room temperature from simple precursors and isolated in near-quantitative yields. ESI-MS, NMR spectroscopy, and diffusion ordered spectroscopy confirm the identity and homogeneity of the trimetallic products. In comparison with monometallic model complexes, analysis of UV/Vis absorption, steady-state photoluminescence and time-resolved emission reveals the impacts of supramolecular assembly on the photophysical properties. UV/Vis absorption and cyclic voltammetry suggest perturbation of some frontier orbital energies as a result of assembly, and the emission spectra and lifetimes reveal efficient excited-state energy transfer via a Dexter mechanism, and show that the site of luminescence (platinum or iridium) depends on the identity of the cyclometalating ligand bound to iridium.     

Synthesis,structure, and electrochemistry of mer[RuCl3(DMSO–S)(DMSO–O)(py)]

Reaction of mer-[RuCl₃(DMSO–S)₂(DMSO–O] (1) with pyridine (py) in dichloromethane yields mer-[RuCl₃(DMSO–S)(DMSO–O)(py)] (2). A single crystal suitable for X-ray diffraction was obtained by recrystalization with dichloromethane and diethyl ether. X-ray diffraction analysis revealed an unusual case in which two independent molecules (2a and 2b) are present in the asymmetric unit cell. Both molecules have distorted octahedral geometry in which DMSO is bound through oxygen and sulfur. Density functional theory (DFT) calculations were performed for 2a and 2b in gas phase to investigate bonding shown by the two DMSO ligands. Optimizations were done on both DMSO ligands bonded through S, both DMSO ligands bonded through O, one DMSO bonded through O, and the other through S but opposite to the actual molecule. The energy differences of the optimized structures were calculated.     

Synthesis,Characterization and Crystal Structures of Two New Compounds of Polyoxometalates and Diaminocyclohexanetetraacetate–Copper Complexes

The two new compounds (NH₄)₂[Cu₅(H₂O)₁₀(DCTA)₂] [β-Mo₈O₂₆]·4H₂O (1) and Cu₂[Cu₃K₂(H₂O)₁₀(DCTA)₂(HBW₁₂O₄₀)]·14H₂O (2) (DCTA = 1,2-diaminocyclohexanetetraacetate anion) were synthesized in aqueous solutions and characterized by elemental analyses, TGA, IR spectroscopy and single-crystal X-ray diffraction technique. Single-crystal structure analyses indicate they are constructed by the complexes with different nuclearity and polyoxometalates. In 1 DCTA chelates Cu2 ion and bridges Cu1 and Cu3 ions, forming a tetra-nuclear-ring cation chain extending along [110] direction. In 2 DCTA chelates Cu2/Cu1 and combines Cu3 and K ions, leading to a cyclic ten-heteronuclear complex cation; the K2 ions combine the complex cations and BW₁₂O₄₀ ^5? anions, forming a complex cation-BW₁₂ layer extending on ab-plane. The variable-temperature magnetic susceptibilities of newly prepared crystalline sample of 1 were measured and 1 exhibits a weak antiferromagnetic interaction.     

Dielectric Study of Charge-transfer Complexes in Binary and Ternary Systems at 35°C

Abstract

The measurements of dielectric constant of a number of binary and ternary mixtures of butyl acetate, butyl alcohol, quinoline, pyridine and o-cresol in carbon tetrachloride and benzene have been made at 35°C. Molecular interaction of these aromatic compounds have been studied in terms of variations in parameters; ‘dipole moment’ (μ), ‘interaction dielectric constant’ (δ?), ‘molecular polarisation’ (P) and ‘excess polarisation’ (P_E ). The dipole moment has been calculated using Hysken's method, the interaction dielectric constant utilizing the equation of ideal mole fraction law and excess polarisation using the theory of Erap and Glasstone. The positive values of δ?₁₂ for binary mixtures of quinoline and butyl acetate in carbon tetrachloride and benzene have been attributed to the formation of charge transfer complexes. The negative values of δ?₁₂ and δ?₁₂₃ with pyridine suggest that charge transfer interaction is weakened by pyridine in its binary and ternary mixtures. The plot between the excess polarisation value and the product of mole fractions yielded a straight line passing through the origin showing the formation of charge transfer complexes.