Luminescence of the compounds Y0.5-xLi1.5VO4 :(Dy3+,Eu3+)

In this paper for the first time the compounds Y0.5-xLi1.5VO4:(Dy3+, Eu3+),(YLV:Dy,Eu) (0.01

Triplex selective 2-(2-naphthyl)quinoline compounds: Origins of affinity and new design principles

A novel competition dialysis assay was used to investigate the structural selectivity of a series of substituted 2-(2-naphthyl)quinoline compounds designed to target triplex DNA. The interaction of 14 compounds with 13 different nucleic acid sequences and structures was studied. A striking selectivity for the triplex structure poly dA:[poly dT](2) was found for the majority of compounds studied. Quantitative analysis of the competition dialysis binding data using newly developed metrics revealed that these compounds are among the most selective triplex-binding agents synthesized to date. A quantitative structure-affinity relationship (QSAR) was derived using triplex binding data for all 14 compounds used in these studies. The QSAR revealed that the primary favorable determinant of triplex binding free energy is the solvent accessible surface area. Triplex binding affinity is negatively correlated with compound electron affinity and the number of hydrogen bond donors. The QSAR provides guidelines for the design of improved triplex-binding agents.

Liquid crystal alignment generated by linearly polarized UV light on photoactive low molecular mass compounds

Alignment films prepared from low molar mass photo-crosslinkable materials containing the cinnamate group can be used for aligning LCs after irradiating the films with linearly polarized UV light. The high contrast observed in the polarizing optical microscope between dark and bright images indicates that the alignment is quite uniform. As the photoreaction progresses. the average roughness of the films is increased. All the aggregate structures, 'lamellar crystals'. produced by the photo-crosslinking reaction are of a square shape.

Synthesis and crystal structure of bis (tert-butyl-cyclopentadienyl)erbium ethoxide, (t-BuCp)(2)ErOEt

The formation of ( t-BuCp)(2)ErOEt was discussed. Its single-crystal structure was determined by X-ray diffraction. The crystal is monoclinic, P2(1)/c space group, a = 1.0191(2), b = 1.6203(5), c = 1.2118(3) nm, beta = 102. 960( 10)degrees, V = 1.9500 (nm(3)), Z = 2, D-c = 1.566 mg . m(-3), R = 0.0450, R-w = 0.1363. The complex is monomeric and solvent-free in the solid state. The erbium ion is coordinated by two tert-butyl-cyclopentadienyl rings and one oxygen atom of ethoxy group to form a seven-coordinated complex.

Hybrid organic-inorganic compounds doped with terbium carboxyl complexes produced in situ via a sol-gel approach

In situ synthesis of terbium carboxyl complexes in an organic-inorganic hybrid matrix by a sol-gel process has been proposed. The formation of terbium carboxyl complexes in the hybrid matrix is confirmed by the luminescence spectra and IR spectra. It is observed that the location at the amino group in aminobenzoic acid has a large effect on the luminescence properties and lifetimes. Furthermore, the emission intensity decreases with increasing temperature.

Expert system for elucidation of structures of organic compounds (ESESOC) - Algorithm on stereoisomer generation

An algorithm for enumeration of stereoisomers due to asymmetric carbon, C=C double bond and so on has been developed. It consists of three steps. The output of stereoisomers can be represented by 2.5-dimensional connection table.

Investigation of covalency and spectrum shifts in 3d transition-metal compounds

By using a correction factor of d electron effects on bond, PV theory is applied to the calculation of chemical bond;parameters of d transition-metal compounds. Racah parameters and Mossbauer isomer shifts are calculated, and the results are agreement with the experimental values.

Fullerenes-extracted soot: a new adsorbent for collecting volatile organic compounds in ambient air

Fullerenes-extracted soot (FES) is the by-product of fullerenes production. Retention characteristics at different temperatures for 17 volatile organic compounds (VOCs) on FES are measured. The adsorption and desorption efficiencies for VOCs on FES adsorbent tubes range from 40.8 to 117%, most of them being 100+/-20%. The values are compared with Tenax GR, an adsorbent commonly used in environmental analysis. FES can be used as an adsorbent of low cost to collect VOCs in environmental samples. (C) 2000 Elsevier Science B.V. All rights reserved.

Spectroscopy of several beta-diketone compounds and their tautomers

Six beta-diketone compounds, 1,3-bis(4-nitrophenyl)-1,3-propanedione (1), 1-(4-nitrophenyl)-3-(3-nitrophenyl)-1,3-propanedione(2), 1,3-bis(3-nitrophenyl)-1,3-propanedione(3) 1,3-bis(4-amimophenyl)-1,3-propanedione(4), 1-(4-amimophenyl)-3-( 3-amimophenyl)-1,3-propanedione(5) and 1,3-bis (3-amimophenyl)-1,3-propanedione(6) were synthesized, Their structures were characterized by IR, UV-Vis, fluorescence and NMR spectroscopy, The percentage of keto tautomer, enol-keto equilibrium constant and enol tautomer ratio of them were also determined, The percentage of keto tautomer is increased in the order from compound 1 to 3 and decreased in the order from compound 4 to 6, which show the effect of substituent on the tautomer. The results of enol tautomer ratio of compounds 2 and 5 indicated that b-form of enol is slightly more favorable than its a-form.

Theoretical studies of nonlinear optical properties of compounds K(4)Ln(2)(CO3)(3)F-4 (Ln=Pr, Nd, Sm, Eu, Gd)

K(4)Ln(2)(CO3)(3)F-4 (Ln=Pr, Nd, Sm, Eu, Gd) is a special type of frequency doubling compound, whose crystal structure exhibits a scarcity of fluorine ions. This leads to two different coordination polyhedrons in the general position of K(2) atoms: [K(2)O6F(1)(2)F(2)] and [K(21)O6F(1)(2)] in a 2/1 ratio. The chemical bonding structures of all constituent atoms of the compound K4Gd2(CO3)(3)F-4 (KGCOF) are comprehensively studied; moreover, the relationship between the chemical bonding structure and the nonlinear optical (NLO) properties is investigated from the chemical bond viewpoint. The theoretical prediction of the NLO tensor coefficient d(11) of KGCOF is in agreement with experimental observation. Theoretical analyses show that the nonlinearity of this crystal type mainly originates from K-O bonds. In addition, the correlation between the NLO tensor d(11) and the refractive index n(0) of KGCOF is discussed. (C) 2000 American Institute of Physics. [S0021-8979(00)07506-X].

Quantitative structure-property relationship research to the analysis of photoionization sensitivity of organic compounds in gas chromatography

The A(m) index and molecular connectivity index were used for studying the photoionization sensitivity of some organic compounds in gas chromatography. The analysis of structure-property relationship between the photoionization sensitivity of the compounds and the A(m) indices or molecular connectivity indices has been carried out. The genetic algorighm was used to build the correlation model in this field. The results demonstrate that the property of compounds can be described by both A(m) indices and molecular connectivity indices, and the mathematical model obtained by the genetic algorithm was better than that by multivariate regression analysis.

The development in oxidation of olefins to ketones catalyzed by palladium compounds

The development in the oxidation of olefins to ketones catalyzed by palladium compounds was reviewed. Some improved methods for the oxidation of olefins catalyzed by Wacker-type catalyst systems are also summarized. For this reaction, some new catalyst systems and the reaction mechanism are described. Emphasis has been given to the applications of Pd(I)/HPA(heteropoly acid), Pd(I)/FePc (iron phthalocyanine), Pd (I)/HQ (hydroquinone)/FePc, Pd (I)/HQ/HPA, Pd (I)/CuSO4/HPA catalyst systems in the oxidation of olefins to ketones; the application of Pd(I)/LCoNO2, PdCl2 (MeCN)(2)/CuCl, Pd(OAc)(2)/ pyridine, fluorous biphasic catalyst systems in the oxidation of olefins to ketones is also surveyed.

Amperometric tyrosinase biosensor based on a sol-gel-derived titanium oxide-copolymer composite matrix for detection of phenolic compounds

A new type of tyrosinase biosensor was developed for the detection of phenolic compounds, based on the immobilization of tyrosinase in a sol-gel-derived composite matrix that is composed of titanium oxide sol and a grafting copolymer of poly(vinyl alcohol) with 4-vinylpyridine. Tyrosinase entrapped in the composite matrix can retain its activity to a large extent owing to the good biocompatibility of the matrix. The parameters of the fabrication process and the variables of the experimental conditions for the enzyme electrode were optimized. The resulting sensor exhibited a fast response (20 s), high sensitivity (145.5 muA mmol(-1) 1) and good storage stability. A detection limit of 0.5 muM catechol was obtained at a signal-to-noise ratio of 3.

Synthesis and characterization of metallocenes containing tert-butyl substituted cyclopentadienyl ligands and their activities in ethylene polymerization

The metallocene complexes ((BuC5H4)-Bu-t)(2)MCl2 (M=Ti (1a), Zr (1b), Hf (1c)) and (tBu2C5H3)(2)MCl2 (M=Ti (2a), Zr (2b), Hf (2c)) were synthesized by the react ions of Li (BuC5H4)-Bu-t and (LiBu2C5H3)-Bu-t with metal tetrachloride in THF solution. The complexes were characterized by their IR, H-1-NMR and EI-MS. The molecular structure of Ic was determined by X-ray single-crystal structure analysis. The complexes (1a similar to 2c) exhibited high activities for ethylene polymerizatin (up to 3.2x10(6) gPE/mol.h) in the presence of methylaluminoxane (MAO) at room temperature.

Investigation of the model compounds at 4-aminobenzoic acid modified glassy carbon electrode by scanning electrochemical microscopy

In this paper, we studied the reactions of both potassium ferricyanide and hexaammineruthenium(III) chloride at a 4-aminobenzoic acid (4-ABA) modified glassy carbon electrode (GCE) by scanning electrochemical microscopy (SECM) in different pH solutions. The surface of the modified electrode has carboxyl groups, the dissociation of which are strongly dependent upon the solution pH values. The rate constant kb of the oxidation of ferrocyanide on the modified electrode can be obtained by fitting the experimental tip current-distance (I-T-d) curves with the theoretical values. The surface pK(a) of the 4-ABA modified GCE was estimated from the plot of standard rate constant k(o) versus the solution pH and is equal to 3.2, which is in good agreement with the reported result. The SECM approach curves for Ru(NH3)(6)(3+) both on the bare and the modified electrodes show similar diffusion control processes. These results can be explained by the electrostatic interactions between the modified electrode surface and the model compounds with different charges. (C) 2001 Elsevier Science BN. All rights reserved.