Naohisa Yanagihara

Synthesis and nonlinear optical behavior of Ag nanoparticles in PMMA

In this work we have synthesized silver nanoparticles in Poly (methyl methacrylate) (PMMA). This was achieved by polymerizing the mixture of monomer and corresponding metal compound, followed by post-heating treatment. The linear absorption coefficient of the samples was measured using a spectrophotometer, where an absorption peak at 420nm was observed. This peak grows up and shifts as a function of the concentration of the radical initiator. The linear refractive index was measured using the Fresnel equations and agrees with previous reported results. The nonlinear properties were obtained using the single lens Z-scan method, where the nonlinear absorption coefficient (Δα) was found between 5.5975514 and 17.9483493cm-1. The nonlinear refractive index coefficient (Δη) was found to be negative and its value oscillates between 12.9099 E-06 and 22.4276 E-06. Finally, the third-order coefficient (χ(3)) was calculated in the range of 233-787 E-9 esu.

Syntheses and crystal structures of oxovanadium(IV) complexes with N,N′-ethylenebis(amino acids)

Abstract The oxovanadium(IV) complexes with N,N′-ethylenebis(amino acids) ([VO(XeX)(H2O)], where X=A ((S)-Ala), V ((S)-Val) and P ((S)-Pro)) are synthesized and characterized by X-ray analyses and IR spectra. The crystal structure analyses reveal that the geometry around the vanadium cation of each complex is distorted octahedral and is coordinated by a water molecule and the tetradentate N,N′-ethylenebis(amino acidate) anion with Δ-cis-α configuration, in which the water oxygen atom occupies equatorial coordination position and one of the two secondary or tertiary nitrogen atoms of each tetradendate ligand is bound trans to the vanadyl oxo moiety. The compilation of bond lengths for present and previous VO complexes containing nitrogen and oxygen donating ligands shows that the tertiary amine groups of PeP ligand elongate VN bonds. Comparison of the sum of the bond angles of three five-membered rings (one ethylenediamine ring and two amino acidate rings) indicates that the ring strain is mostly concentrated in the ethylenediamine ring and the strain of amino acidate ring lying in the equatorial plane of V(IV) ion is more pronounced than that in another amino acidate ring. The IR observations of the present complexes are well consistent with the crystallographic studies of them.

Complex formations of silver(I) trifluoroacetate and trifluoromethanesulfonate with benzene and cyclohexene

Abstract An apparatus for measurements of equilibrium ligand vapor pressure has been applied in order to determine the stoichiometry of benzene and cyclohexene complexes of silver(I) trifluoroacetate (AgCF 3 CO 2 ) and silver(I) trifluoromethanesulfonate (silver(I) triflate, AgCF 3 SO 3 ) in the solid state. It has been found that the equilibrium leads the formation of such complexes as: (AgCF 3 CO 2 ) 2 (C 6 H 6 ), (AgCF 3 CO 2 ) 2 (C 6 H 10 ), (AgCF 3 CO 2 ) 2 (C 6 H 10 ) 3 , (AgCF 3 SO 3 ) 2 (C 6 H 6 ), (AgCF 3 SO 3 )(C 6 H 6 ), (AgCF 3 SO 3 )(C 6 H 10 ) and (AgCF 3 SO 3 )(C 6 H 10 ) 2 . The temperature dependence of the gas-solid equilibrium ligand pressure has also been examined for these complexes, and the enthalpy and entropy changes according to the following complex dissociation reactions were estimated: (AgCF 3 CO 2 )L m (s) ⇄ AgCF 3 CO 2 (s)+mL (g): and (AgCF 3 SO 3 )L n (s) ⇄ AgCF 3 SO 3 (s)+nL (g), where Ls are benzene and cyclohexene. On the basis of the thermodynamic data obtained, the effects of the counter anion as well as the ligand on the complex stability are discussed.

A thermal study of several lanthanide triflates

Abstract Five lanthanide triflates, Ln(TfO) 3 · n H 2 O, where TfO − =CF 3 SO 3 − , Ln=La 3 , Nd 3 , Sm 3 , Gd 3 and Yb 3 , and n =9 and 13, have been prepared and the thermal decomposition processes of these triflates up to 600°C were characterized by means of TG, DTA, XRD. The thermal studies have shown almost all the lanthanide triflates prepared in this study to exist as a stable nonahydrate. During the stepwise dehydration processes, it was found that mono-, di-, tri-, penta-, and heptahydrates were formed. Decompositions were found to be exothermic, and calcinations of these triflates at 600°C resulted in the formation of the corresponding LnF 3 . Crystal systems of the trifluorides thus obtained were hexagonal for La, Nd and Sm trifluorides, whereas those of Gd and Yb were found to be orthorhombic. The volatile decomposition products at 600°C were identified by MS, and it was revealed that the over all reaction scheme for the thermal decomposition proceeds as follows: Ln(OTf) 3 →LnF 3 +3SO 2 +CO 2 +CF 3 OCF 3 .

SILVER COMPLEXES OF POLY(METHYLPHENYLSILOXANE) FOR SEPARATION OF ALIPHATIC, OLEFINIC AND AROMATIC HYDROCARBONS BY GAS CHROMATOGRAPHY AND DETERMINATION OF THE π-COMPLEX FORMATION CONSTANTS

Abstract Silver trifluoroacetate and trifluoromethanesulfonate become highly soluble to poly(methylphenylsiloxane) because of the ions coordination to the phenyl group: the resulting solution is highly stable. The silver trifluoroacetate or trifluoromethanesulfonate solution has been employed as the liquid phase in gas-liquid chromatography in order to study the separation of mixtures of cyclohexane, cylcohexene and benzene in the temperature range from 50 to 170°C. Use of an internal standard, such as cyclohexane, enables one to evaluate the complex formation constants as well as the salting-out effect merely by measuring the retention time in the presence or absence of Ag+. The complex formation constants of some aromatic and gaseous olefinic compounds have been determined.

Thermal decomposition of oxovanadium(IV) complexes with N,N′-ethylenebis(amino acids)

Abstract Six oxovanadium(IV) complexes with N , N ′-ethylenebis(amino acid) of general formula, [VO(XeX)(H 2 O)]· n H 2 O, where e and X represent ethylene group and ( S )-α-amino acid, respectively; and X=G (Gly) 1 , ( S )-A (Ala) 2 , ( S )-V (Val) 3 ·2H 2 O, ( S )-P (Pro) 4 , m G or G m (Sar or N -methylglycine) 5 ·H 2 O and ( S )-M (Met) 6 ) were prepared. These complexes were characterized by means of TG, DTA, and XRD, and the thermal decomposition processes of these complexes up to 650°C were investigated. The thermal studies showed that the dehydration processes for 3 and 5 having water of crystallization were endothermic, whereas decompositions of all the complexes were exothermic. Calcinations of these complexes at 650°C resulted in the formation of vanadium(V) oxide V 2 O 5 . Choosing 1 as a leading example of the oxovanadium(IV) complexes, an over all reaction scheme for the thermal decomposition was proposed on the basis of IR and MS analyses of both the solid and the volatile decomposition products at different temperatures.

Preparation and characterization of Ag-cluster in poly(methylmethacrylate)

Solid sols of silver in poly(methylmethacrylate), Ag/PMMA, were prepared by bulk polymerization of methyl methacrylate (MMA) with benzoyl peroxide (BPO) as an initiator in the presence of silver(I) trifluoroacetate. Ag/PMMAs were characterized by visible spectroscopy. Effects of the concentration of initiator, the concentration of silver(I) complex and the heat-treatment time on the formation of silver cluster were studied in detail.

Formation of Tetramethylene Sulfoxide via Oxidation of Tetrahydrothiophene by Copper(II)

Reaction of copper(II) p-toluenesulfonate with tetrahydrothiophene (THT) forms a THT cation radical and a THT dication by stepwise one-electron oxidation by Cu2+. Generation of a dimeric species of THT dication is proposed to explain the formation of tetramethylene sulfoxide (TMSO) upon hydrolysis of the dimeric THT dication with H2O.

CO2 Emission Reduction and CO2 Fixation on the Ground by Using Supercritical Carbon Dioxide as an Alternative to Organic Solvents

Publisher Summary In the chemical industry, the majority of chemical products are organic compounds. In many organic chemical industries, most organic compounds are produced in organic solvents because organic compounds are rarely soluble in water. After use, solvents are incinerated and discharged as carbon dioxide into the air. Therefore, the use of supercritical carbon dioxide in place of traditional organic solvents could reduce carbon dioxide emissions. In organic synthesis, carbon-carbon bond formation reactions are the most important reactions, which are conducted in organic solvents and incinerated and discharged as carbon dioxide in the air after the use. The carbon dioxide fixation reactions have been developed as carbon-carbon bond formation reactions to produce carboxylic acids and esters in supercritical carbon dioxide, in place of traditional organic solvents. These reactions in supercritical carbon dioxide are more effective than that of the reaction in organic solvents. These technologies can replace the traditional reactions in organic solvents and contribute to carbon dioxide emission reduction.

Linear and nonlinear optical characterization of PMMA clusters with Ni nanoparticles dispersed

We analyze linear and no linear optical properties of PMMA clusters in thin film s with Ni nanoparticles dispersed with different concentrations. Saturable absorber and negative nonlinear refraction index behavior evidences were found using z-scan technique. We also show that these properties have not dependence of the type of matrix but they have on concentration.