Syntheses,structure, and photoluminescence properties of the 1-dimensional chain compounds [(TPA)(2)Au][Au(CN)(2)] and (TPA)AuCl (TPA = 1,3,5-triaza-7-phosphaadamantane)

The structures and temperature-dependent photoluminescence properties of the one-dimensional compounds [(TPA)(2)Au][Au(CN)(2)], 1, and (TPA)AuCl, 2, are reported. An extended linear chain with weak Au.Au interactions along the c-axis is evident in the structure of 1, and a helical chain with a pitch of 3.271 A is seen for 2. The intrachain Au...Au separation is 3.457(1) and 3.396(2) A in 1 and 2, respectively. As a result of this weak Au...Au interaction, the physical properties of these compounds are anisotropic. Scanning electron microscopy (SEM) studies indicate that single crystals of both compounds are noninsulating. Single crystals of 1 do not luminesce visibly, but grinding the crystals finely initiates a strong green emission under UV irradiation at room temperature. Further interesting optical properties include the dependence of the emission profile of the powder on the exciting wavelength and luminescence thermochromism. When excited at wavelengths < 360 nm, the powder exhibits a blue emission at 425 nm while excitation with longer wavelengths leads to a green emission near 500 nm. While the green emission dominates at ambient temperature, cooling to cryogenic temperatures leads to the dominance of the blue emission. Fibers of 2 are luminescent at 78 K with an emission band centered at 580 nm. Compound 1 crystallizes in the orthorhombic space group Cccm (No. 66), with Z = 2, a = 6.011(1) A, b = 23.877(6) A, c = 6.914(1) A, V = 992.3(3) A(3), and R = 0.0337. Compound 2 crystallizes in the trigonal space group R3 (No. 148), with Z = 18, a = 22.587(2) A, b = 22.587(2) A, c = 9.814(2) A, V = 4336 A(3), and R = 0.0283.     

Physical,chemical and biological studies on transition metal complexes of chelating tridentate ligand

Summary The interaction of 1-benzoin-4-phenylthiosemicarbazone (H₂ BPS) with some transition metal ions has been investigated. The ligand can function as a tridentate chelating agent, giving M(HBPS)₂ and M(BPS). Potentiometric studies proved that the mechanism of chelation is based on hydrogen ion liberation. Spectral studies in solution show that the ligand could be used for the microdetermination of Cu^IIions. On the basis of magnetic and spectral data, an octahedral structure is proposed for the Co^II and Ni^II complexes and a square-planar structure for the Cu^II complex. The corrosion inhibition of aluminium in Cl₃CCO₂H using H₂BPS is studied. The electrical conductivity of H₂BPS and of its complexes have been measured. The ligand shows an activation energy in the range of semiconducting materials. The antimicrobial activity of all compounds has also been demonstrated.     

Catalytic kinetic determination of ultratrace amounts of ruthenium(III) based on the oxidation of hematoxylin by hydrogen peroxide

A new catalytic method was described for the determination of ruthenium(III) based on its catalytic effect on the oxidation of hematoxylin by hydrogen peroxide in weakly acidic medium. The reaction was followed spectrophotometrically by measuring the absorbance of hematoxylin at 440 nm. Under the optimum conditions, ruthenium(III) can be determined in the range 5–120 ng/ml with a relative standard deviation of 1.1%. The mean value of reaction rate constant was 0.012±0.04 min^–1 and the activation energy was 10.45 kJ/mol. The method was tested for the determination of ruthenium(III) in some synthetic mixtures.     

Synthesis of natural pulvinic acids based on a ‘[3+2] cyclization-Suzuki cross-coupling’ strategy

A number of pulvinic acid natural products were prepared based on Suzuki cross coupling reactions of α-hydroxy-γ-alkylidenebutenolides which are readily available by cyclization of 1,3-bis-silyl enol ethers with oxalyl chloride. The formal total synthesis of pulvinic acid, atromentic acid, gomphidic acid and of 4-hydroxypulvinic acid, 4′-hydroxypulvinic acid and iso-gomphidic acid are reported. In addition, total syntheses of pinastric acid, xerocomic acid and variegatic acid were accomplished.     

A simple and green procedure for the conjugate addition of thiols to conjugated alkenes employing polyethylene glycol (PEG) as an efficient recyclable medium

Polyethylene glycol (PEG) is found to be an inexpensive, nontoxic, environmentally friendly reaction medium for the conjugate addition of thiols to conjugated alkenes to afford the corresponding adducts in excellent yields under mild and neutral conditions. Products of undesirable side reactions resulting from polymerization are not observed. The use of PEG avoids the use of either acid or base catalysts for this conversion and moreover PEG can be recovered and reused.     

Enantioselective epoxidation of alkenes catalyzed by 2-fluoro-N-carbethoxytropinone and related tropinone derivatives

Several alpha-substituted N-carbethoxytropinones have been evaluated as catalysts for asymmetric epoxidation of alkenes with Oxone, via a dioxirane intermediate. alpha-Fluoro-N-carbethoxytropinone (2) has been studied in detail and is an efficient catalyst which does not suffer from Baeyer-Villiger decomposition and can be used in relatively low loadings. This ketone was prepared in enantiomerically pure form using chiral base desymmetrization of N-carbethoxytropinone. Asymmetric epoxidation catalyzed by 2 affords epoxides with up to 83% ee. Among other derivatives tested, the alpha-acetoxy derivative 7 affords the highest enantioselectivities.     

Alkylation of 2‐pyridinones: Synthesis of novel acyclonucleosides

This paper presents the synthesis of some novel acyclonucleosides containing 2‐pyridinones and 2‐hydroxyethoxymethyl, 2,3‐dihydroxy‐propyl side chain. The tosylate of these nucleosides analogues could be modified to azido derivatives. Also, acyclonucleosides with 1‐ethoxymethyl, 1‐benzyloxymethyl, 1‐methylthiomethy 1 and 2‐hydroxyethyl side chains have been investigated. The O‐alkylated pyridine derivatives were obtained during most reactions.     

Thermal and electrical behaviour of nickel(II) and copper(II) complexes of 4-acetylamino-2-hydroxy-5-methylazobenzene

The thermal behaviour of the entitled nickel(II) and copper(II) complexes of ¯4-acetylamino-2-hydroxy-5-methyl azobenzene has been studied by means of differential thermal analysis (DTA), thermogravimetry (TG), X-ray powder diffraction, IR and electrical conductivity. A light has been thrown on the nature of interaction of the solvents of crystallization with the host complex. Some of the kinetic parameters are calculated and discussed.     

Enaminones in heterocyclic synthesis: Synthesis and chemical reactivity of 3‐anilino‐1‐substituted‐2‐propene‐1‐ one

The 3‐anilinoenones 3a,b were prepared from the corresponding 3‐dimemyl‐aminopropenones. The reactivity of 3a,b towards a variety of carbon and nitrogen nucleophiles as well as naphthoquinones is reported.     

Ion exchangers as catalysts. II. Catalytic decomposition of hydrogen peroxide with resin-ethylenediamine-copper(II) complex ions

Summary The slow decomposition of H₂O₂ in the presence of Dowex-50 W resin in the form of an ethylenediaminecopper(II) complex ion in water is accompanied by an induction period. The reaction is first order with respect to [H₂O₂] and the rate constant (perg of dry resin) was deduced. Autocatalytic behaviour was found for the H₂O₂ decomposition with 2% crosslinked divinylbenzene. The induction period disappeared and the reaction rate increased when the decomposition was carried out with a resin in the form of a peroxo-copper complex, which proves that the formation of an intermediate (active species) retards the reaction rate. The precursor of the active species, formed during the induction period, was not the amine-copper(II) complex ion but a product of the latter with H₂O₂. It proved impossible to carry out the decomposition in acid or buffer solutions, in which the resin is regenerated.