First 5f-element complexes with the tetradentate BTBP ligand. Synthesis and crystal structure of uranyl(VI) compounds with CyMe4BTBP

Treatment of [UO2(OTf)(2)] or [UO2I2(thf)(3)] with 1 equiv. of CyMe4BTBP in anhydrous acetonitrile led to the formation of [UO2(CyMe4BTBP)(OTf)(2)] (1) and [UO2(CyMe4BTBP)I-2] (2) which crystallized as the cationic forms [UO2(CyMe4BTBP)(py)][OTf](2) (3) and [UO2I(CyMe4BTBP)][I] (4) in pyridine and acetonitrile, respectively. These compounds are unique examples of structurally characterized actinide complexes with a BTBP molecule; this ligand adopts a planar conformation in the equatorial plane of the {UO2}(2+) ion. In pyridine, 1 is dissociated into [UO2(OTf)(2)(PY)(3)] and free CyMe4BTBP and the thermodynamic parameters (K, Delta H, Delta S) of this equilibrium have been determined by H-1 NMR spectroscopy. The ethoxide derivative [UO2(OEt)(CyMe4BTBP)][OTf] (5) crystallized from a solution of I in a mixture of ethanol and acetone under air, and the dinuclear mu-oxo complex [{UO2(CyMe4BTBP)}(2)(mu-O)][I](2) (6) was obtained from [UO2I(thf)(2.7)] and CyMe4BTBP. The crystal structures of 6 and of the analogous derivatives [{UO2(py)(4)}(2)(mu-O)][I](2)(7) and [{UO2(TPTZ)(py)}(2)(mu-O)][I-3](2)(8) exhibit a flexible [{UO2}-O-{UO2}](2+) moiety.

Pyrene-functionalised, alternating copolyimide for sensing nitroaromatic compounds

A novel, pyrene-functionalised copolymer has been synthesised in a single step via imidisation of poly(maleic anhydride-alt-1-octadecene) with 1-pyrenemethylamine, and its potential for the detection of volatile nitro aromatic compounds (NACs) evaluated. The new copolymer forms complexes in solution with NACs such as 2,5-dinitrobenzonitrile, as shown by H-1 NMR, UV-vis and fluorescence spectroscopy. Moreover, thin films of this copolymer, cast from THF solution, undergo almost instantaneous fluorescence quenching when exposed to the vapour of 2,5-dinitrobenzonitrile (a model for TNT) at ambient temperatures and pressures.

A DFT study of free radicals formed from artemisinin and related compounds

Ab initio calculations using density functional theory have shown that the reactions that occur between artemisinin, 1, a cyclic trioxane active against malaria, and some metal ions and complexes lead to a series of radicals which are probably responsible for its therapeutic activity. In particular it has been shown that the interaction of Fe(H) with artemisinin causes the O-O bond to be broken as indeed does Fe(III) and Cu(I), while Zn(II) does not. Calculations were carried out with Fe(II) in several different forms including the bare ion, [Fe(H2O)(5)](2+) and [FeP(Im)] (P, porphyrin; Im, imadazole) and similar results were obtained. The resulting oxygen-based radicals are readily converted to more stable carbon-based radicals and/or. stable products. Similar radicals and products are also formed from two simple model trioxanes 2 and 3 that show little or no therapeutic action against malaria although some subtle differences were obtained. This suggests that the scaffold surrounding the pharmacophore may be involved in molecular recognition events allowing efficient uptake of this trioxane warhead into the parasite. (C) 2004 Elsevier B.V. All rights reserved.

The gas-phase ozonolysis of unsaturated volatile organic compounds in the troposphere

The gas-phase reactions of ozone with unsaturated hydrocarbons are significant sources of free radical species (including (OH)-O-center dot) and particulate material in the Earth's atmosphere. In this tutorial review, the kinetics, products and mechanisms of these reactions are examined, starting with a discussion of the original mechanism proposed by Criegee and following with a summary presentation of the complex, free radical-mediated reactions of carbonyl oxide (Criegee) intermediates. The contribution of ozone-terpene reactions to the atmospheric burden of secondary organic aerosol material is also discussed from the viewpoint of the formation of non-volatile organic acid products from the complex chemistry of ozone with alpha-pinene. Throughout the article, currently accepted understanding is supported through the presentation of key experimental results, and areas of persistent or new uncertainty are highlighted.

Synthesis and characterization of carbamoyl methyl pyrazole(CMPz) compounds of palladium(II) chloride: the crystal and molecular structure of [PdCl2{(C3H3N2CH2CONBu2)-Bu-i}(2)]

Carbamoyl methyl pyrazole compound of palladium(II) chloride of the type [PdCl2L2] (where L = C5H7N2CH2CON(C4H9)(2), C5H7N2CH2CON((C4H9)-C-i)(2), C3H3N2CH2CON(C4H9)(2), or C3H3N2CH2CON((C4H9)-C-i)(2)) has been synthesized and characterized by IR and H-1 NMR spectroscopy. The structure of the compound [PdCl2{(C3H3N2CH2CONBu2}2)-Bu-i] has been determined by single crystal X-ray diffraction and shows that the ligands are bonded through the soft pyrazolyl nitrogen atom to the palladium(II) chloride in a trans disposition. (c) 2007 Elsevier B.V. All rights reserved.

Oxidation of biogenic and water-soluble compounds in aqueous and organic aerosol droplets by ozone: a kinetic and product analysis approach using laser Raman tweezers

The results of an experimental study into the oxidative degradation of proxies for atmospheric aerosol are presented. We demonstrate that the laser Raman tweezers method can be used successfully to obtain uptake coeffcients for gaseous oxidants on individual aqueous and organic droplets, whilst the size and composition of the droplets is simultaneously followed. A laser tweezers system was used to trap individual droplets containing an unsaturated organic compound in either an aqueous or organic ( alkane) solvent. The droplet was exposed to gas- phase ozone and the reaction kinetics and products followed using Raman spectroscopy. The reactions of three different organic compounds with ozone were studied: fumarate anions, benzoate anions and alpha pinene. The fumarate and benzoate anions in aqueous solution were used to represent components of humic- like substances, HULIS; a alpha- pinene in an alkane solvent was studied as a proxy for biogenic aerosol. The kinetic analysis shows that for these systems the diffusive transport and mass accommodation of ozone is relatively fast, and that liquid- phase di. ffusion and reaction are the rate determining steps. Uptake coe. ffcients, g, were found to be ( 1.1 +/- 0.7) x 10(-5), ( 1.5 +/- 0.7) x 10 (-5) and ( 3.0 - 7.5) x 10 (-3) for the reactions of ozone with the fumarate, benzoate and a- pinene containing droplets, respectively. Liquid- phase bimolecular rate coe. cients for reactions of dissolved ozone molecules with fumarate, benzoate and a- pinene were also obtained: k(fumarate) = ( 2.7 +/- 2) x 10 (5), k(benzoate) = ( 3.5 +/- 3) x 10 (5) and k(alpha-pinene) = ( 1-3) x 10(7) dm(3) mol (-1) s (- 1). The droplet size was found to remain stable over the course of the oxidation process for the HULIS- proxies and for the oxidation of a- pinene in pentadecane. The study of the alpha- pinene/ ozone system is the first using organic seed particles to show that the hygroscopicity of the particle does not increase dramatically over the course of the oxidation. No products were detected by Raman spectroscopy for the reaction of benzoate ions with ozone. One product peak, consistent with aqueous carbonate anions, was observed when following the oxidation of fumarate ions by ozone. Product peaks observed in the reaction of ozone with alpha- pinene suggest the formation of new species containing carbonyl groups.

DNA cleavage and antitumour activity of platinum(II) and copper(II) compounds derived from 4-methyl-2-N-(2-pyridylmethyl)aminophenol: spectroscopic, electrochemical and biological investigation

The reaction of the redox-active ligand, Hpyramol (4-methyl-2-N-(2-pyridylmethyl)aminophenol) with K2PtCl4 yields monofunctional square-planar [Pt(pyrimol)Cl], PtL-Cl, which was structurally characterised by single-crystal X-ray diffraction and NMR spectroscopy. This compound unexpectedly cleaves supercoiled double-stranded DNA stoichiometrically and oxidatively, in a non-specific manner without any external reductant added, under physiological conditions. Spectro-electrochemical investigations of PtL-Cl were carried out in comparison with the analogue CuL-Cl as a reference compound. The results support a phenolate oxidation, generating a phenoxyl radical responsible for the ligand-based DNA cleavage property of the title compounds. Time-dependent in vitro cytotoxicity assays were performed with both PtL-Cl and CuL-Cl in various cancer cell lines. The compound CuL-Cl overcomes cisplatin-resistance in ovarian carcinoma and mouse leukaemia cell lines, with additional activity in some other cells. The platinum analogue, PtL-Cl also inhibits cell-proliferation selectively. Additionally, cellular-uptake studies performed for both compounds in ovarian carcinoma cell lines showed that significant amounts of Pt and Cu were accumulated in the A2780 and A2780R cancer cells. The conformational and structural changes induced by PtL-Cl and CuL-Cl on calf thymus DNA and phi X174 supercoiled phage DNA at ambient conditions were followed by electrophoretic mobility assay and circular dichroism spectroscopy. The compounds induce extensive DNA degradation and unwinding, along with formation of a monoadduct at the DNA minor groove. Thus, hybrid effects of metal-centre variation, multiple DNA-binding modes and ligand-based redox activity towards cancer cell-growth inhibition have been demonstrated. Finally, reactions of PtL-Cl with DNA model bases (9-Ethylguanine and 5'-GMP) followed by NMR and MS showed slow binding at Guanine-N7 and for the double stranded self complimentary oligonucleotide d(GTCGAC)(2) in the minor groove.

Low temperature CO oxidation on supported and unsupported gold compounds

Several simple gold compounds and their physical mixtures with TiO2 Were tested for low temperature CO oxidation. No true catalytic activity was found for gold precursors on their own, although both Au2O3 and Au(OH)(3) react well with CO even at room temperature in a non-catalytic manner. Despite that catalytic activity was obtained by physically mixing Au(OH)(3) or Au2O3 with TiO2 and the results further emphasise the importance of a good contact between the gold and the support for good CO oxidation activity. (c) 2005 Published by Elsevier.

Simple general method of generating non-oxo, non-amavadine model octacoordinated vanadium(IV) complexes of some tetradentate ONNO chelating ligands from various oxovanadium(IV/V) compounds and structural characterization of one of them

A simple general route of obtaining very stable octacoordinated non-oxovanadium( IV) complexes of the general formula VL2 (where H2L is a tetradentate ONNO donor) is presented. Six such complexes (1-6) are adequately characterized by elemental analysis, mass spectrometry, and various spectroscopic techniques. One of these compounds (1) has been structurally characterized. The molecule has crystallographic 4 symmetry and has a dodecahedral structure existing in a tetragonal space group P4n2. The non-oxo character and VL2 stoichiometry for all of the complexes are established from analytical and mass spectrometric data. In addition, the non-oxo character is clearly indicated by the complete absence of the strong nu(v=o) band in the 925-1025 cm(-1) region, which is a signature of all oxovanadium species. The complexes are quite stable in open air in the solid state and in solution, a phenomenon rarely observed in non-oxovanadium(IV) or bare vanadium(IV) complexes.

Volatile compounds produced by the probiotic strain Lactobacillus plantarum NCIMB 8826 in cereal-based substrates

The production of volatile compounds by the probiotic strain, Lactobacillus plantarum NCIMB 8826, in cereal-based media (oat, wheat. barley and malt) was investigated. Sixty compounds, including fatty acids and their esters, amides, alcohols, aldehydes, aromatic hydrocarbons, furans, ketones, peroxides and pyrans, were identified. L. plantarum significantly changed the aroma profile of the four cereal broths. and each substrate showed a specific volatiles profile. Oat and barley media were the substrates more influenced by the fermentation process. The most abundant volatiles detected in oat, wheat, barley and malt were oleic acid, linoleic acid. acetic acid, and 5-hydroxymethylfurfural, respectively. Analysis of these products confirmed the heterofermentative pathway of L plantarum. Maillard compounds were not detected during sterilisation and fermentation. This study is the first to report the volatile composition of probiotic drinks produce with non-supplemented cereal-based media and the results obtained could contribute to the development of new non-dairy probiotic formulations. (C) 2009 Elsevier Ltd. All rights reserved.

Critical stages of the brewing process for changes in antioxidant activity and levels of phenolic compounds in ale

Samples were taken at each stage of brewing (malt, milling, mashing, wort separation, hop addition, boiling, whirlpool, dilution, fermentation, warm rest, chill-lagering, beer filtration, carbonation and bottling, pasteurization, and storage). The level of antioxidant activity of unfractionated, low-molecular-mass (LMM) and high-molecular-mass (HMM) fractions was measured by the 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfortic acid) radical cation (ABTS(.+)) and ferric-reducing antioxidant power (FRAP) procedures. Polyphenol levels were assessed by HPLC. The LMM fraction (<5 kDa) was responsible for similar to80% of the level of antioxidant activity of the unfractionated malt and beer samples. In the unfractionated samples, significant decreases (P < 0.001) in antioxidant activity levels were observed after milling and beer filtration, with the decrease after beer filtration being accompanied by a significant decrease (P > 0.001) in catechin and ferulic acid levels. Increases in antioxidant activity levels were observed after mashing, boiling, fermentation, chill-lagering, and pasteurization, in line with previous studies on lager. Additionally, increases in the level of antioxidant activity occurred after wort separation and carbonation and bottling and were accompanied by increases in levels of most monitored polyphenols. Data from the ABTS(.-) and FRAP assays indicated that the compounds contributing to the levels of antioxidant activity responded differently in the two procedures. Levels of ferulic, vanillic, and chlorogenic acids and catechin accounted for 45-61% of the variation in antioxidant activity levels.

Interaction of sulphur-containing aroma compounds with proteins in both model systems and real food systems

Irreversible binding of key flavour disulphides to ovalbumin has been shown previously to occur in model systems. The extent of binding is determined by the availability of the sulphydryl groups to participate in disulphide exchange, influenced either by pH, or the state of the protein (native or heat-denatured). In this study, two further proteins, one with sulphydryl groups available in the native state (beta-lactoglobulin) and one with no sulphydryl groups in the native state (lysozyme) were used to confirm this hypothesis. When the investigation was extended to real food systems, a similar effect was shown when a commercial meat flavouring containing disulphides was added to heat-denatured ovalbumin. Furthermore, comparison of the volatiles generated from onions, cooked either alone, or in the presence of meat, showed a significant reduction of key onion-derived disulphides when cooked in the presence of meat, and an even greater reduction of trisulphides. These findings may have implications for consumer acceptance of food products; where these compounds are used as flavourings or where they occur naturally.

Interactions of ferric ions with olive oil phenolic compounds

The ferric complexing capacity of four phenolic compounds, occurring in olives and virgin olive oil, namely, oleuropein, hydroxytyrosol, 3,4-dihydroxyphenylethanol-elenolic acid (3,4-DHPEA-EA), and 3,4-dihydroxyphenylethanol-elenolic acid dialdehyde (3,4-DHPEA-EDA), and their stability in the presence of ferric ions were studied. At pH 3.5, all compounds formed a reversible 1:1 complex with ferric ions, but hydroxytyrosol could also form complexes containing > 1 ferric ion per phenol molecule. At pH 5.5, the complexes between ferric ions and 3,4-DHPEA-EA or 3,4-DHPEA-EDA were relatively stable, indicating that the antioxidant activity of 3,4-DHPEA-EA or 3,4-DHPEA-EDA at pH 5.5 is partly due to their metal-chelating activity. At pH 7.4, a complex containing > 1 ferric ion per phenol molecule was formed with hydroxytyrosol. Oleuropein, 3,4-DHPEA-EA, and 3,4-DHPEA-EDA also formed insoluble complexes at this pH. There was no evidence for chelation of Fe(II) by hydroxytyrosol or its derivatives. At all pH values tested, hydroxytyrosol was the most stable compound in the absence of Fe(III) but the most sensitive to the presence of Fe(III).

Effects of enrichment of refined olive oil with phenolic compounds from olive leaves

The possibility of preparing olive oil, with the same nutritional value and stability characteristics found in virgin olive oil, by the enrichment of refined olive oil with olive leaf polyphenols was studied. To obtain antioxidant phenols similar to those found in virgin olive oil, these components were extracted from the leaves of several olive cultivars from the Northern region of Portugal, namely, Carrasca, Ripa, Negruche, Cordovil, Verdeal, Madural, and Bical cultivars, under several conditions. The concentration of a leaf extract required for addition to refined olive oil to obtain the same stability as virgin olive oil was determined. The extract from 1 kg of leaves was sufficient to fortify 50-320 L of refined olive oil to a similar stability as a virgin olive oil sample depending on the metal concentration of the oil, cultivar, and time of the year when the leaves were picked.