Dielectric Relaxation in Glycine–Water and Glycine–Ethanol–Water Solutions Using Time Domain Reflectometry

Dielectric relaxation measurements on water–ethanol–glycine ternary system were carried out using time domain reflectometry (TDR) at 25, 30, 35, and 40°C in the frequency range from 10 MHz to 10 GHz. Glycine–ethanol–water solutions are prepared with different concentrations of ethanol (0, 5, 10, 15, 20, and 30%) and also for different glycine molar concentrations (0, 0.2, 0.4, 0.6, 0.8, and 1 M). The dielectric relaxation parameters are measured for aqueous glycine solutions also to compare the results with those for the glycine–ethanol–water ternary system. For all the mixtures considered, only one relaxation peak was observed in this frequency range. All the mixtures display a Cole–Davidson dispersion. The relaxation peaks shift to lower frequency with an increase in glycine concentration and also with ethanol concentration. The logarithm of the relaxation time log() shows a nonlinear relation with glycine concentration which implies a change of relaxation mechanism with glycine concentration. The dielectric strength for these mixtures shows a nearly linear relation with glycine molar concentration.     

Complex Formation Equilibria and Molecular Structure of Divalent Metal Ions–Vitamin B3–Glycine Oligopeptides Systems

Complex formation of divalent transition metal ions (copper(II), cobalt(II) and nickel(II)), vitamin B3 (nicotinic acid) and glycine oligopeptides (glycine, glycylglycine, glycyl-l-phenylalanine, and glycylglycylglycine) were studied at 298 K in aqueous solutions using the pH-potentiometric technique. The copper Cu(II), cobalt Co(II), and nickel Ni(II) complexing capacity of vitamin B3 in the absence and in the presence of glycine peptides and their overall stability constants in aqueous solutions were obtained and explained by the HYPERQUAD 2008 program using the potentiometric data. From the protonation and complex formation constants, representative complex species distribution diagrams were obtained using HYSS 2009 software. The UV–Vis spectroscopic, cyclic voltammeteric and conductometric titration measurements were carried out to give qualitative information about the conformation of the complexes formed in these solutions and their stoichiometric ratios. The Gibbs energies and the molecular structures of the complexes were evaluated and predicted using Gaussian 09 software molecular modeling and density functional theory calculations.     

Synthesis and Characterization of Two Extended High-dimensional Architectures Formed by Transition Metal–Glycine Complexes

Under the same experimental condition, changing the kinds of the transition metal (TM) of the reaction, we gained two new compounds: Na₃[Cu(Gly)₂][Cr(OH)₆Mo₆O₁₈]·13H₂O 1, and NaCo₂(gly)₆ClO₄ 2. Compound 1 exhibits an unusual three-dimensional (3D) network constructed from [Cr(OH)₆Mo₆O₁₈]³⁻ building blocks, trinuclear Na⁺ ions and [Cu(gly)₂] coordination complexes as linkers, representing the first example of a 3D extended framework based on Anderson type polyanions and amino acid molecules. Compound 2 consists of an unusual 3D network grafted with Na[Co(gly)₃]₆ complexes. Moreover, compound 2 contains left-handed and right-handed helical chains. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Dielectric Studies of Glycine–Ethylene Glycol–Water Solutions Using Time Domain Reflectometry

Time domain reflectometry (TDR) has been used for dielectric relaxation measurements on the glycine–ethylene glycol–water ternary system (TDR) at 25, 30, 35, and 40°C in the frequency range from 10 MHz to 10 GHz. Glycine–ethylene glycol–water solutions are prepared with different concentrations of ethylene glycol (0, 5, 10, 15, 20, and 30%) and also for different glycine molar concentrations (0, 0.2, 0.4, 0.6, 0.8, and 1 M). The dielectric relaxation parameters are measured for aqueous glycine solutions also to compare the results with those for the glycine–ethylene glycol–water ternary system. For all the solutions considered, only one relaxation peak was observed in this frequency range. The complex permittivity spectra for the aqueous glycine solutions can be well described by the Cole–Davidson expression, whereas that for the ternary system can be well described by the Havriliak–Negami expression. The logarithm of the relaxation time log() shows a nonlinear relation with the glycine molar concentration that implies a change in the relaxation mechanism with glycine concentration. The dielectric strength increases with an increase in glycine molar concentration, whereas it decreases with an increase in ethylene glycol concentration.     

Heat Capacities and Thermodynamic Properties of Lanthanum/Holmium Perchlorate Complexes with Glycine

IntroductionSinceAnghilerietal.1reportedin 1975thatthecom plexoflanthanumchloridewithglycinehadanti canceref fect,complexesofrareearthwithaminoacidhavebeenex tensivelystudied .Inthepastdecades,about 2 0 0kindsofcomplexesofrare earthcompoundswithaminoacidshavebeensynthesizedandstudied .2 Theycanbeusedasantisepticandanticancerdrugsinmedicine,additivesofanimalforageandfertilizerinagriculture,andwooldyeintextileindus try .3,4 Complexesofrareearthwithaminoacidwerewidelyusedinmanyfields,however,the…     

Heat Effect of the Protonation of Glycine and the Enthalpies of Resolvation of Participating Chemical Species in Water–Dimethylsulfoxide Solvent Mixtures

Enthalpies of the protonation of glycine in water?dimethylsulfoxide (DMSO) mixed solvents are determined calorimetrically in the range of DMSO mole fractions of 0.0 to 0.9, at T = 298.15 K and an ionic strength μ = 0.3 (NaClO₄). It is established that the protonation of glycine becomes more exothermic with an increasing mole fraction of DMSO, and the enthalpies of resolvation of glycine and glycinium ions in water?DMSO solvent mixtures are calculated. It is shown that the small changes in the enthalpy of protonation observed at low mole fractions of DMSO are caused by the contributions from the solvation of proton and protonated glycine cancelling each other out. The enthalpy term of the Gibbs energy of the reaction leading to the formation of glycinium ion is estimated along with the enthalpy of resolvation of the reacting species in the water?DMSO mixed solvent.     

The Effect of Concentration Parameters on Complexation in the Iron(0)–Iron(II)–Glycine–Water System

The processes of formation of iron(II) complexes in aqueous glycine solutions in the pH range of 1.0–8.0 at 298 K and ionic strength of 1 mol/L (NaClO₄) are studied using Clark and Nikolskii’s oxidation potential method. The type and number of coordinated ligands, the nuclearity, and the total composition of the resulting complexes are determined. The following complex species are formed in the investigated system: [Fe(OH)(H₂O)₅]⁺, [FeHL(H₂O)₅]²⁺, [Fe(HL)(OH)(H₂O)₄]⁺, [Fe(OH)₂(H₂O)₄]⁰, [Fe₂(HL)₂(OH)₂(H₂O)₈]²⁺, and [Fe(HL)₂(H₂O)₄]²⁺. Their formation constants are calculated by the successive iterations method using Yusupov’s theoretical and experimental oxidation function. The model parameters of the resulting coordination compounds are determined.     

Heat Capactites and Thermodynamic Properties of Lanthanum／Holmium Perchlorate Complexes with Glycine

The heat capacities of the two complexes, [La₂(Gly)₆(H₂O)₄]‐(ClO₄)₆ and [Ho₂(Gly)₄(H₂O)₄](ClO₄)₆·2H₂O (Gly = glycine), were measured by adiabatic calorimetry in the temperature range from 78 to 375 K. A solid‐solid phase transition was found between 322.87 and 342.29 K for [Ho₂(Gly)₆(H₂O)₄](ClO₄)₆·2H₂O, and the peak temperature, the enthalpy and the entropy of the transition were obtained to be 330.94 K, 11.65 kJ·mol^?1 and 35.20 J· K^?1·mol^?1, respectively. No indication of any phase transition or thermal anomaly was observed for [La₂ (Gly)₆ (H₂O)₄ ] (ClO₄)₆. Thermal stabilities of the two complexes were investigated by thermogravimetry in the temperature range of 40–800°C. The possible mechanisms for the thermal decompositions were proposed according to the TG and DTG curves.     

Bubble points of hydrogen chloride–water–isopropanol and hydrogen chloride–water–isopropanol–benzene systems and liquid–liquid equilibria of hydrogen chloride–water–benzene and hydrogen chloride–water–isopropanol–benzene systems

Bubble points of the HCl–water–isopropanol and the HCl–water–isopropanol–benzene systems and liquid–liquid equilibria (LLE) of the HCl–water–benzene and the HCl–water– isopropanol–benzene systems were measured at 25–85°C and 30–70°C, respectively. The electrolyte nonrandom two-liquid model proposed by Chen et al. [C.-C. Chen, H.I. Britt, J.F. Boston, L.B. Evans, AIChE J. 28 (1982) 588–596] can satisfactorily correlate bubble points and liquid–liquid equilibria of the present mixed-solvent electrolyte systems over the entire range of temperature and concentrations using only binary adjustable parameters.     

Electrochemical and structural characterization of sputter-deposited Mg–Nb and Mg–Nb–Al–Zn alloy films

Nanocrystalline Mg–Nb and Mg–Nb–Al–Zn alloy films were deposited by dc magnetron sputtering on glass and quartz substrates in a wide range of niobium concentrations from 6 to 80 at.%. Structural, electrochemical and corrosion properties of the films were studied by X-ray diffraction, dc voltammetry, electrochemical impedance spectroscopy and electrochemical quartz crystal microbalance. Development of body-centred cubic Nb structure in the Mg–Nb alloy matrix yielded the effects of lattice contraction, grain refining and electrochemical passivity. The measurements showed high corrosion resistance of the films in alkaline solutions when niobium content was one third or more. An increased corrosion resistance was achieved by introducing minor amounts of Al (ca. 2 at.%). In particular, such Al effect was pronounced at lower Nb concentrations (20 to 30 at.%). Semiconductor properties of spontaneously formed oxide on Mg–Nb alloy were studied by Mott–Schottky plots, which indicated highly doped n-type oxide structures on Mg–Nb surface. The paper fills some gap in understanding of niobium–magnesium systems, which show potential for applications in hydrogen storage, switchable mirrors and corrosion protection.     

Electrochemical and microgravimetric characterization of magnetron-sputtered Fe–Cr–Ni–Ta and Fe–Cr–Ni alloy films in neutral and strongly acidic media

The Fe–Cr–Ni and Fe–Cr–Ni–Ta alloy films were deposited on quartz substrates by magnetron-sputtering using targets of AISI 316 stainless steel and in combination with pure tantalum. The conventional melting of the Fe–Cr–Ni–Ta alloy formed is virtually impossible because the melting point of tantalum is higher than the boiling points of the other components. Elemental content of the films was determined by XPS analysis. Corrosion behaviour of both alloy films was studied in 5% NaCl and 10 M HCl by electrochemical quartz crystal microgravimetry (EQCM), electrochemical impedance spectroscopy (EIS) and dc-voltammetry. The corrosion resistance of Fe–Cr–Ni–Ta appeared to be significantly higher than that of Fe–Cr–Ni in both neutral (5% NaCl) and strongly acidic (10 M HCl) media. The Fe–Cr–Ni–Ta specimen exhibited an extremely high corrosion resistance in 10 M HCl, where the corrosion rates were about one order of magnitude lower than those of Fe–Cr–Ni in neutral solution. EQCM measurements in NaCl solution indicated accumulation of corrosion products on the Fe–Cr–Ni–Ta surface, which was evident from a distinctive increase in electrode mass. By contrast, the mass of the tantalum-free alloy film decreased with a constant rate, which indicated alloy dissolution to prevail. The corrosion current calculated from the mass decrease was in good agreement with that derived from voltammetric measurements. The EQCM data showed that the corrosion resistance of the Fe–Cr–Ni–Ta alloy film in 10 M HCl was about two orders of magnitude higher than that of the Fe–Cr–Ni.     

The density and surface tension of In–Sn and Cu–In–Sn alloys

Abstract  

The density and surface tension of binary In–Sn and ternary Cu–In–Sn alloys have been measured by a sessile-drop method. Decrease of the density and of the surface tension was observed with rising temperature. With increased Sn content in the alloys, the density increased while the surface tension reduced slightly. Addition of Cu could significantly increase the density and surface tension in the Cu–In–Sn system. The surface tension of the Cu–In–Sn alloys was also calculated by means of Butler’s equation, and compared with experimental values, showing good agreement.     

Versatile Spirocyclic Glycine‐Based Nitrones and Their Highly Stereoselective 1,3‐Dipolar Cycloaddition

A convenient and efficient method for the synthesis of novel spirocyclic nitrones prepared from glycine derivatives is reported. The 1,3‐cycloaddition reactions of the nitrones with alkenes lead to novel isoxazolidines in high yields and with excellent regio‐ and stereoselectivity.     

Trimetallic Nickel–Lanthanum and Nickel–Gadolinium Metallomesogens

Adducts were formed between a mesomorphic Ni(salen) complex [salen=2,2′-N,N′-bis(salicylidene)ethylenediamine] with six terminal alkoxy chains and a lanthanide nitrate (Ln=La, Gd). Different alkoxy chain lengths were used: OC¹²H²⁵, OC¹⁴H²⁹, OC¹⁶H³³ and OC¹⁸H³⁷. Trinuclear nickel–lanthanum and nickel–gadolinium complexes [Ln(NO³)³{Ni(salen)}²] were obtained. The compounds exhibit a wide-temperature-range hexagonal columnar mesophase (Col^H) with rather low melting points. The mesophase stability ranges of both the parent nickel complexes and the nickel–lanthanide complexes decrease with increasing chain length. A decrease in the mesophase stability range over the lanthanide series was also observed. The results are compared with those of similar copper–lanthanide complexes. A marked difference is the higher thermal stability of the nickel–lanthanide complexes in comparison with the copper–lanthanide complexes.     

Z- and E-selective Horner–Wadsworth–Emmons reactions

In the present work, we determined and evaluated the stereochemical outcome of the Horner–Wadsworth–Emmons (HWE) reaction of 2-oxoalkylphosphonates with different ester functions (bis(2,2,2-trifluoroethyl), 2,2,2-trifluoroethyl methyl, dimethyl) and side chains (aliphatic, aromatic) with three different aldehydes (benzaldehyde, THP- and PPB-protected Corey aldehydes) under two reaction conditions. The “trans” protocol is generally used in the E-selective HWE reactions, while “cis” protocol promotes the Z-selectivity.     

The Synthesis, Crystal Structure and Thermoanalysis of N-Salicylidene Glycine Tripyridine Nickel( Ⅱ )

Introduction Complexes of some Schiff bases with transition metals are widely used, for example, they can be used as anticancer medicine, preservative, complex reagent and the model of the biological oxygen carrier. So their syntheses, properties and application have been intensively studied. In order to study the relationship between the     

Synthesis and Crystal Structure of a Heptanuclear Trigonal Prismatic Cluster {PrCu_6} with Glycine and Imidazole as Ligands

A new heptanuclear trigonal prismatic cluster [PrCu6(μ3-OH)3(Gly)6im6](ClO4)6 was synthesized through the self-assembly of Pr^3 , Cu^2 , glycine and imidazole in aqueous solution and characterized by X-ray structure analysis. The compound belongs to the trigonal R3 space groupwith a=b=15.8761(2), c=23.4943(5) A, V=5128.4(1)A^3, Z=3, Dc=1.965 g/cm^3,μ=2.869mm^-1 F(000)=3012, the final R=0.0332 and wR=0.0844 for 3596 independent reflections. In the cation, the Pr3 ion is situated at the center of a prism formed by six copper atoms and coordinates to nine oxygen atoms with a tricapped trigonal prismatic coordination polyhedron. Six glycine ligands and six imidazole terminal ligands participate in constructing the cluster.