Search

We comprehensively examined fulvic acids isolated from three lakes in Vestfold Hills, eastern Antarctica and microbial reference fulvic acid from Pony Lake located in western Antarctica. These fulvic acids were compared in terms of their structural similarities and differences by means of elemental analysis, cross polarisation magic-angle spinning (CP-MAS) 13C NMR spectroscopy, X-ray photoelectron spectroscopy (XPS) and tetramethylammonium hydroxide (TMAH) thermochemolysis coupled to gas chromatography-mass spectrometry (GC-MS). The results indicate that these Antarctic fulvic acids show notable differences in chemical composition and structure; in particular XPS demonstrates that the distribution of nitrogen-containing compounds in the nitrogen-rich Antarctic fulvic acids differ significantly from each other. The dissimilarities are also highlighted in terms of quantity and quality of their nitrogenous constituents. For instance, Organic Lake Fulvic Acid (OLFA) contains around 10 times lower amide groups (pyrimidine-peptide N) than Pendant Lake Fulvic Acid (PNFA). It also shows 1.5 times less quaternary amine than Mossel Lake Fulvic Acid (MLFA) and PNFA. According to CP-MAS 13C NMR experiments the carbohydrate content in Vestfold Hills fulvic acid is higher than that of Pony Lake Fulvic Acid (PLFA), suggesting that dissolved organic matter (DOM) from Vestfold Hills Lakes is immature. TMAH-GC-MS demonstrated that Antarctic fulvic acids are enriched in heterocyclic non-aromatic nitrogencontaining components such as pyrimidine structures, with the exception of OLFA. Furthermore, tricyclic terpenoids (dehydroabietic acid) were detected in two out of four fulvic acids tabulated using TMAH-GC-MS. Although diterpenes are commonly associated with plants and fungi, their occurrence in Antarctic fulvic acids could be justified due to their diverse origins from cyanobacteria to aerosols. [ABSTRACT FROM AUTHOR]

The amount of rutile phase in chromium-doped titania photocatalyst was controlled by varying stirring time (0.5-2.0h) at room temperature during a sol-gel synthesis process. The percentage of rutile phase increased from 15.1% to 28.6% when stirring time was prolonged from 0.5 to 1.5h. Further increases in the stirring time had negligible effect on the rutile phase amount. As evidenced by analyses using diffuse reflectance ultraviolet-visible spectroscopy and X-ray photoelectron spectroscopy, a sufficient stirring time was important for more substitution of Cr[sup 3+]forTi[sup 4+] in the lattice, resulting in anatase-to-rutile phase transformation. The formation of more rutile phase in Cr-doped TiO[sub 2] not only reduced the band gap energy, but also induced surface defects that retarded electron-hole recombination. It has been demonstrated that the Cr-doped TiO[sub 2] prepared with a stirring time of 1.5h possessed the lowest band gap energy of 1.89eV, and hence it achieved the highest photodegradation of methylene blue under visible light irradiation. [ABSTRACT FROM AUTHOR]

Two novel coordination compounds, namely, [Sm[sub 2](pypza)[sub 2](H[sub 2]O)[sub 10]]Cl[sub 4]·H[sub 2]O (1) and [Eu(pypza)(C[sub 2]O[sub 4])] (2), where pypza=3-(2-pyridyl)-1-pyrazolyl acetato, have been synthesized under hydrothermal conditions. These compounds were characterized by elemental analysis, infrared spectroscopy, and single-crystal X-ray diffraction. The X-ray diffraction analysis reveals that compound 1 displays double one-dimensional chains, whereas 2 shows a two-dimensional layer structure via the bridging pypza and oxalate (C[sub 2]O[sub 4][sup 2-]) which may arise from the oxidation of hydroacetic acid through the decomposition and hydrolysis of Hpypza by means of the cleavage of the C-N bond between the carboxylate group and the pyrazolyl ring. Compounds 1 and 2 show three-dimensional networks by hydrogen bonding interactions. Furthermore, the luminescence properties of 1 and 2 have also been investigated at room temperature in the solid state. [ABSTRACT FROM AUTHOR]

Based on the ligand 1,4-bis(2-(diphenylphophino)benzylideneamino)benzene (pbb), two complexes, [Cu[sub 2](pbb)(2,2'-bipyridine)[sub 2]](BF[sub 4])[sub 2] (1) and [Cu[sub 2](pbb)(phen)[sub 2]](BF[sub 4])[sub 2] (2), have been prepared and characterised by IR, [sup 1]H NMR, [sup 31]P NMR, [sup 19]F NMR, and [sup 11]B NMR spectroscopy and X-ray crystal structure analysis. Structural analysis reveals that complexes 1 and 2 contain 1D infinite chains and 2D supramolecular networks constructed by C-H···π and π···π interactions, and an ordered-layer-lattice of BF[sub 4][sup -] is located between these 2D networks. The results show that C-H···π and π···π interactions play an important role in the formation of 2D supramolecular networks. The UV-vis absorption peaks of complexes 1 and 2 display intraligand charge transfer and metal to ligand charge transfer (MLCT) absorption. Complexes 1 and 2 display efficient luminescent emission assigned to MLCT excited states, and the maximum emissions of these complexes in acetonitrile solution are different from those of the solid-state samples. In addition, complexes 1 and 2 have been exploited as sensitisers in dye-sensitised solar cells, and efficiencies are also observed. [ABSTRACT FROM AUTHOR]

A new pyrene derivative bearing a modifiable silyl function (electron-donating group) and cyano function (electron-withdrawing group) was synthesized as a labelling agent for biological substances. The modified pyrene exhibited a marked bathochromic shift in both absorption and fluorescence spectra. The fluorescence quantum yield of the modified pyrene was also significantly increased compared with that of the unmodified pyrene. The modified pyrene was successfully incorporated into oligoDNA. [ABSTRACT FROM AUTHOR]

Methylenecycloheptadienyne 11 (heptafulvyne) is obtained very cleanly by flash vacuum thermolysis (FVT) of the diazobenzocyclobutene precursor 8 at 4008C followed by isolation as a neat solid at 77 K or in an Ar matrix at 7-10 K. Compound 11 is a yellow solid, stable till ~ -100°C in the neat state. The diazo compound itself (2) is observable by IR spectroscopy following mild decomposition of the tosylhydrazone salt 1 at 115°C. FVT of 8 at 200°C also generates diazo compound 2 as observed by IR spectroscopy and on-line mass spectrometry. FVT of 8 at 600-800°C causes rearrangement of 11 to phenylacetylene 12 and benzocyclobutadiene 13. Mechanisms for the rearrangements are proposed. Facile rearrangement of benzocyclobutadiene to phenylacetylene is ascribed to chemical activation, which is also seen to be involved in the rearrangement of p-, m-, and o-phenylenebiscarbenes 25-27 to phenylacetylene 12. [ABSTRACT FROM AUTHOR]

The article presents a science experiment based on alloying buffer layers in colloidal CdSe and ZnS core and shell nanocrystals. Topics discussed include decrease of photoluminescent (PL) quantum yield, X-Ray photoelectron spectroscopy analysis, and formation of the interfacial alloy during the epitaxy procedure.

The use of N-acetyl-L-methionine (NAM) as a bio-available source for methionine supplementation as well as its ability to reduce the toxicity of acetaminophen poisoning has been reported. Its interaction with the complex physiological matrix, however, has not been thoroughly investigated. This manuscript reports on the kinetics and mechanism of oxidation of NAM by acidic iodate and aqueous iodine. Oxidation of NAM proceeds by a two electron transfer process resulting in formation of a sole product: N-acetyl-L-methionine sulfoxide (NAMS=0). Data from electrospray ionization mass spectrometry confirmed the product of oxidation as NAMS=0. The stoichiometry of the reaction was deduced to be IO[sub 3] + 3NAM → r + 3NAMS=0. In excess iodate, the stoichiometry was deduced to be 2IO3 + 5NAM + 2H+ → I[sub 2] + 5NAMS=0 + H[sub 2]0. The reaction between aqueous iodine and NAM gave a 1:1 stoichiometric ratio: NAM +I[sub 2] + H[sub 2]0 → NAMS=0 + 2I- + H+. This reaction was relatively rapid when compared with that between NAM and iodate. It did, however, exhibit some auto-inhibitory effects through the formation of triiodide (I3) which is a relatively inert electrophile when compared with aqueous iodine. A simple mechanism containing 11 reactions gave a reasonably good fit to the experimental data. [ABSTRACT FROM AUTHOR]

Continuous-flow microreactors offer major advantages for photochemical applications. This mini-review summarizes the technological development of microflow devices in the Applied and Green Photochemistry Group at James Cook University, and its associates, from fixed microchips for microscale synthesis to flexible multicapillary systems for parallel photochemistry. Whereas the enclosed microchip offered high space-time-yields, the open capillary-type reactor showed a greater potential for further modifications. Consequently, a 10-microcapillary reactor was constructed and used successfully for process optimization, reproducibility studies, scale-up, and library synthesis. To demonstrate the superiority of microflow photochemistry over conventional batch processes, the reactors were systematically evaluated using alcohol additions to furanones as model reactions. In all cases, the microreactor systems furnished faster conversions, improved product qualities, and higher yields. UVC-induced [2+2] cycloadditions of furanone with alkenes were exemplarily examined in a capillary reactor, thus proving the broad applicability of this reactor type. [ABSTRACT FROM AUTHOR]

The adduct of borabenzene (C[sub 5]H[sub 5]B) and pyridine (C[sub 5]H[sub 5]N) was studied by means of quantum-chemical ab initio and time-dependent density functional theory calculations at different levels of theory. In the fully optimized structure (MP2/6-311++G**) of the free donor-acceptor complex (C[sub 2]), the C-B-C angle amounts to 120.6°. The planes of the two aromatic rings enclose a torsion angle of ~40° with a barrier to rotation about the B-N bond of less than 3 kcal mol[sup -1] (1 kcal mol[sup -1] = 4.186kJ mol[sup -1]). The highest computational level applied in this study (complete basis set limit, coupled cluster with single and double excitations (CCSD)) results in an energy associated with the reaction of borabenzene with pyridine of -52.2 kcal mol[sup -1]. Natural bond orbital analyses were performed to study the bond between the borabenzene and the pyridine unit of the adduct. The UV-vis spectrum of the adduct was calculated employing time-dependent density functional theory methods and the symmetry-adapted cluster-configuration interaction method. Our calculated electronic excitation spectrum of the pyridine adduct as well as its spectrum of the normal modes qualitatively reproduce the characteristic features of the IR and the UV-vis spectra described by experimentalists and thus allows assignment of the observed absorption bands, which in part agree with those by other authors. [ABSTRACT FROM AUTHOR]

The synthesis and characterisation of a new anthracycline, 3'-azidodaunorubicin semicarbazone (ADNRS) is reported. The interaction between ADNRS and calf thymus DNA (ctDNA) was investigated by absorption and fluorescence spectroscopy in combination with melting temperature (T[sub m]) curves and molecular modelling in physiological buffer (pH 7.4). Evidence indicates that ADNRS binds in the groove of ctDNA and the fluorescence quenching mechanism is a static quenching type. Calculated thermodynamic parameters show that hydrophobic interactions may play a predominant role in the binding. Furthermore, molecular modelling results corroborate the spectroscopic investigations. [ABSTRACT FROM AUTHOR]

Optical characterisation using dye molecules as probes was used to study the non-covalent interactions between chemically converted graphene (CCG) and non-conjugated, water soluble polymers in aqueous solution. The strong adsorption of non-conjugated polymers such as poly(ethylene oxide) (PEO) and poly(vinyl alcohol) (PVA) on CCG is observed by fluorescence and ultraviolet-visible spectroscopy and atomic force microscopy, and this leads to desorption of π-conjugated molecules from CCG. Such adsorption/desorption behaviour can be tailored by modifying the molecular weight of polymers and the chemistry of graphene. This finding provides a facile and non-covalent approach to the functionalisation of CCG and opens up new opportunities for the fabrication of graphene/polymer nanocomposites. [ABSTRACT FROM AUTHOR]

Several aromatic and heteroaromatic nitrenes and carbenes undergo photochemical and sometimes also thermal ring opening. Depending on benz-annelation, the ring-opened species may have the character of either nitrenes (for a-annelation) or l,5-(l,7-)-biradicals (for β-annelation). Both types have been observed, and they are clearly distinguished by their characteristic electron spin resonance spectra. In addition, ring opening of hetarylnitrenes to nitrile ylides can be observed whenever there is a meta-relationship between a ring nitrogen atom and the nitrene (or carbene) centre. The factors governing the two types of ring opening have been investigated. The nitrenes and carbenes are generated by either low temperature Ar matrix photolysis or flash vacuum thermolysis of azides, tetrazoles, triazoles, or diazo compounds with matrix isolation of the products. [ABSTRACT FROM AUTHOR]

Three new 2D copper(ii) complexes [Cu(NIPH)(L)] (1), [Cu(BDC)(L)(H[sub 2]O)] (2), and [Cu(HBTC)(L)]·2H[sub 2]O (3) were hydrothermally synthesized by self-assembly of aromatic polycarboxylates (H[sub 2]NIPH = 5-nitroisophthalic acid, H[sub 2]BDC = 1,3-benzenedicarboxylic acid, H[sub 3]BTC = 1,3,5-benzenetricarboxylic acid) and the flexible bis(pyridylamide) ligand L (L = N,N'-di(3-pyridyl)succinamide), and structurally characterized by single crystal X-ray diffraction, and elemental, IR, and thermogravimetric analyses. Compound 1 is a 2D coordination polymer based on tri-flexural helix chains (left-, right-handed [Cu-L] [sub n] helix chains, and left-handed Cu-NIPH helix chain). Compound 2 exhibits a 2D wavelike polymeric layer structure constructed from a 1D [Cu-L] [sub n] sinusoidal chain and a 1D [Cu-BDC] [sub n] V-like chain. Compound 3 possesses a 2D double-layer network formed from 1D [Cu-L] [sub n] zigzag chains and 1D [Cu-HBTC][sub 2] [sub n] double chains. The fluorescent properties of the three compounds and the electrochemical behaviour of compound 2-bulk-modified carbon paste electrode were also studied. Three new 2D copper(ii) complexes were hydrothermally synthesized using a flexible bis(pyridylamide) ligand L as the main ligand and three polycarboxylates as the auxiliary ligands. The fluorescent properties of the three compounds and the electrochemical behaviour of a compound 2-modified carbon paste electrode (2-CPE) were studied. [ABSTRACT FROM AUTHOR]

1-Ethyl-3-Methylimidazolium lactate ([EMIM][LAC]) is an environmental friendly ionic liquid with potential industrial applications. Attenuated total reflectance infrared spectroscopy (ATR-IR) and density functional theory (DFT) calculations were employed to investigate the molecular interactions between methanol and [EMIM][LAC]. The infrared spectra were analyzed by two methods: excess spectroscopy and two-dimensional (2D) correlation spectroscopy. In the ATR-FTIR spectra, v(C4,5-H), v(C2-H), v(alkyl), v(-OD), and v(-COO) all show blue shifts upon addition of methanol. 2D correlation analysis indicated that the v(imidazolium ring C-H) band varies before that of v(alkyl C-H) with increasing CD[sub 3]OD content. The following sequential order of interaction strength is established by DFT calculations: EMIM-methanol -LAC > EMIM-LAC > LAC-methanol > EMIM-methanol. The hydrogen-bonding properties of binary systems consisting of a representative lactate-based ionic liquid (IL) 1-ethyl-3-methylimidazolium lactate ([EMIM][LAC]) and a cosolvent, methanol, have been studied by the combined application of FTIR spectroscopy and DFT calculations over the entire concentration. [ABSTRACT FROM AUTHOR]

Pentachlorophenol (PCP) is an organochloride pesticide banned in many countries due to its broad-spectrum toxicity. Current methods for monitoring PCP in environmental water require expensive laboratory equipment, limiting field monitoring. Two field methods for screening the concentration of PCP in environmental water are described herein. The first involves filtering the sample and calculating the indicative concentration from the absorbance at 320 nm. Alternatively, the sample can be acidified with concentrated hydrochloric acid to produce a fine suspension. This cloudy solution can be matched to a photo card for field estimation of concentration, or calculated more accurately from the absorbance at 450 nm. The useable ranges for these methods are 2 ppb to 100 ppm for the un-acidified method and 4 ppm to 1000 ppm for the acidified method. Results indicate that aquatic humic substances and natural turbidity present in environmental water do not compromise the results. A photochard can be utilized in the field, to give an indicatvie concentration of pentachlorophenol (ppm) in natural water samples. A precise concentration can be determined through the use of UV/Vis spectroscopy (either in the field or laboratory), in the range of 2 ppb-1000 ppm, depending on sample treatment. [ABSTRACT FROM AUTHOR]

The use of pyridine-2,6-dimethanol, pdmH[sub 2], in reactions with nickel(ii) acetate has led to two Ni[sub 4] clusters, depending on the solvent. [Ni[sub 4](O[sub 2]CMe)[sub 4](pdmH)[sub 4]]·MeCN (1·MeCN) can be obtained from MeCN and [Ni[sub 4](O[sub 2]CMe)[sub 6](pdmH)[sub 2](EtOH)[sub 2]]·1.2EtOH (2·1.2EtOH) from EtOH. Each cluster can be converted into the other in the appropriate solvent. The tetranuclear cluster molecule 1 possesses a distorted cubane {Ni[sub 4](μ[sub 3]-OR)[sub 4]}[sup 4+] core (RO[sup -] = pdmH[sup -]) with the Ni[sup II] atoms and the alkoxide-type oxygen atoms from the η[sup 3] : η[sup 1] : μ[sub 3] pdmH[sup -] ligands occupying alternate vertices of the cube; four η[sup 1] : η[sup 1] : μ MeCO[sub 2] [sup -] groups cap four faces of the cube. The four Ni[sup II] atoms in molecule 2 are located at four vertices of a defective dicubane and are bridged by six oxygen atoms, two μ[sub 3] from the η[sup 3] : η[sup 1] : η[sup 1] : μ[sub 3] pdmH[sup -] ligands and four from four monoatomically bridging MeCO[sub 2] [sup -] groups; peripheral ligation is provided by two η[sup 1] : η[sup 1] : μ MeCO[sub 2] [sup -] groups and two terminal EtOH ligands. IR data are discussed in terms of the coordination modes of the ligands. Variable-temperature direct-current magnetic susceptibility data of 1 and 2 were modelled with two and three J values respectively, indicating diamagnetic ground states (S = 0). The sign and the magnitude of the J values are discussed in terms of structural features of the complexes. The first use of pyridine-2,6-dimethanol in Ni[sup II] cluster chemistry has afforded two new tetranuclear complexes through a simple change in the nature of the reaction solvent. Both complexes possess an S = 0 spin ground state, albeit with differences in the strength of the magnetic exchange interactions, as a result of their different metal topology (cubane vs. defective dicubane). [ABSTRACT FROM AUTHOR]

In natural light-harvesting systems, pigment-protein complexes (PPC) convert sunlight to chemical energy with near unity quantum efficiency. PPCs exhibit emergent properties that cannot be simply extrapolated from knowledge of their component parts. In this Perspective, we examine the design principles of PPCs, focussing on the major light-harvesting complex of Photosystem II (LHCII), the most abundant PPC in green plants. Studies using two-dimensional electronic spectroscopy (2DES) provide an incisive tool to probe the electronic, energetic, and spatial landscapes that enable the efficiency observed in photosynthetic light-harvesting. Using the information about energy transfer pathways, quantum effects, and excited state geometry contained within 2D spectra, the excited state properties can be linked back to the molecular structure. This understanding of the structure-function relationships of natural systems constitutes a step towards a blueprint for the construction of artificial light-harvesting devices that can reproduce the efficacy of natural systems. [ABSTRACT FROM AUTHOR]

This paper reviews work carried out in the Centre for Biospectroscopy, Monash University, at the Infrared Microspectroscopy Beamline on the Australian Synchrotron since the first synchrotron light. It discusses the attributes and advantages of the beamline for chemical spectroscopy and imaging of cellular and tissue samples and briefly summarizes new techniques that will come online in the near future. [ABSTRACT FROM AUTHOR]

The design and operation of electrosynthesis cells for generation of samples for X-ray absorption spectroscopy are described. Optimization of continuous-flow methods allows the generation of highly reducing species, which may be combined with spectroscopic validation of the composition of the electrogenerated solution. It is shown that the large sample volume (10 mL) of the 1-10 mM (in the absorbing element) solution required for such experiments can be reduced to ∼100 μL using a strategy in which the in situ electrosynthesis cell is amenable to freeze-quenching and transfer to a beamline cryostat. The working electrode in this case doubles as the X-ray absorption spectroscopy sample cell. The application of these techniques is illustrated by the reduction chemistry of Fe3S2(CO)9, 3Fe2S. Spectra recorded in the near-edge region confirm that quantitative preparation of samples of 3Fe2S, 3Fe2S1- and 3Fe2S2- can be prepared by either approach, but samples of a more reduced form, identified as [Fe3S(CO)9]2-, could only be generated using continuous-flow electrosynthesis techniques. Differences in the structural chemistry of the 3Fe2S0/1-/2- redox series were examined from the perspective of their near-edge spectra and the structures of 3Fe2S1- and 3Fe2S2- forms were deduced by a combination of computational (density functional theory), spectroscopic and X-ray absorption fine-structure analyses. These show that addition of the first electron is predominantly localized in one of the Fe-Fe bonds; cleavage of the Fe-Fe bond by addition of a second electron to the Fe-Fe antibonding orbital is associated with a more substantial rearrangement of the molecule. The reduced compounds have structural similarities to the reduced dithiolate-bridged di-iron hexacarbonyl compounds and this is related to the weak electrocatalytic proton reduction exhibited by Fe3S2(CO)9. The methods described provide a strategy for the collection and analysis of experimental data directed towards structure elucidation of redox-activated solution-state complexes. [ABSTRACT FROM AUTHOR]

Chitosan microcapsules containing calendula oil are prepared by a simple coacervation method. The results show that the performance of the microcapsules, including encapsulation efficiency and particle size, is affected by the change of various processing parameters of microcapsule manufacture. Under the optimal parameter combinations: the chitosan concentration is 1.5?% w/v∼ the core/wall ratio is 0.1?g?mL-1 ∼ the stirring speed is 1200?rpm∼ and the pH value is 10. The compositions and surface morphology of the microcapsules are examined using scanning electron microscope and FTIR spectroscopy. The in vitro cytotoxicity evaluation demonstrates that the microcapsules exhibit no significant cytotoxic effects on human keratinocytes. The in vivo toxicology analysis on mice proves that the microcapsules do not exert any significant necrosis to the liver. It is suggested that our microcapsules could be used as a safe drug carrier both topically and orally. [ABSTRACT FROM AUTHOR]

Hydrophilically substituted diterpenes of the structural class of serrulatanes have attracted attention as novel antibacterial compounds that are effective even against multidrug-resistant Staphylococcus aureus, a key bacterium involved in human infections. The mechanism of action has, however, not been established yet. Available data on structure-activity relationships suggest that the aromatic hydroxy group is essential for activity, and the strongest activity has been found for naphthyl compounds. In this context, it is reported that two highly active serrulatanes isolated from leaf resin of the Australian plant species Eremophila duttonii showed instability upon separation. Acetylation of hydroxy groups generated stable compounds that could be isolated and identified by NMR spectroscopy. The acetylated compounds showed little antibacterial activity, but such activity, as well as oxidative instability, was restored after hydrolysis of the acetate groups. Thus, phenolic hydroxy groups are essential for the mechanism of action of these compounds. The reaction products were not purifiable in sufficient quantities, but indications point to oxidation to quinones. Such oxidation may be a key aspect of the antibacterial activity of this class of compounds. [ABSTRACT FROM AUTHOR]

Chemical fractionation of a southern Australian marine sponge, Trachycladus laevispirulifer, yielded 9-(5′-deoxy-5′-thio-β-d-xylofuranosyl)adenine disulfide as the first recorded natural occurrence of a nucleoside disulfide, and only the second of a xylo-nucleoside. Structure elucidation of the disulfide was achieved by detailed spectroscopic analysis and comparison to synthetic model compounds. The antibacterial, antifungal, and anticancer properties of the disulfide are documented and the literature surrounding natural and synthetic thionucleosides is reviewed. [ABSTRACT FROM AUTHOR]

A new polypyridyl ligand 2-benzo[b]thiophen-3-yl-1H-1,3,7,8-tetraazacyclopenta[l]phenanthrene (BTCP) and its RuIIcomplexes [Ru(bpy)2(BTCP)]2+(1) (bpy = 2,2′-bipyridine), [Ru(phen)2(BTCP)]2+(2) (phen = 1,10-phenanthroline), and [Ru(dmb)2(BTCP)]2+(3) (dmb = 4,4′-dimethyl-2,2′-bipyridine), have been synthesized and characterized. The DNA-binding properties of the three complexes were investigated by spectroscopic methods and viscosity measurements. The results indicate that complexes 1, 2, and 3 bind to DNA by an intercalative mode and the ancillary ligands have a significant effect on the binding strengths of RuIIcomplexes to DNA. When irradiated at 365 nm, complex 2 was found to be a more effective DNA-cleaving agent than complexes 1 and 3. [ABSTRACT FROM AUTHOR]

Outdoor experiments were conducted on a laboratory scale to study the infrared radiation emission of vegetation flames. Measurements were made in the spectral range 1000-4500 cm-1, using a compact and portable Fourier transform infrared spectrometer including an HgCdTe/InSb dual detector. Flame emission was compared with the reference signal emitted by a blackbody surface at 1000 K. We carried out two different series of fire experiments: a series of fires in a 0.45 m-diameter steel tray and a series of wind-tunnel fires. Various types of wild land fuels were used: wood wool, vine branches, dry wood, and Kermes oak branches. From a qualitative observation of emission spectra, it appears that the main contribution comes from the hot gaseous combustion products, with a low-intensity background radiation from soot, as the small-scale flames in these experiments were optically thin. It was also found that, in the flaming combustion zone of the fuel bed, both phases contribute to infrared emission. Our results, in combination with existing data on the absorptivity of vegetation, give a better understanding of radiative transfer in vegetation fires and show how total radiative properties could be deduced from spectral measurements. We believe that this preliminary study provides pilot data for future studies in this area. [ABSTRACT FROM AUTHOR]

The new cyanido-bridged mixed valent FeII/CoIIImacrocyclic complexes [L2CoIII(μ-NC)FeII(CN)5]-and trans-[L2CoIII(μ-NC)FeII(CN)4(μ-CN)CoIIIL2]2+have been prepared and characterized spectroscopically. The trinuclear complex trans-[L2Co(μ-NC)Fe(CN)4(μ-CN)CoL2](ClO4)2·11H2O has been characterized crystallographically. The di- and trinuclear complexes exhibit metal-to-metal charge transfer transitions characteristic of Class II mixed valent chromophores and their redox and spectroscopic properties have been analyzed by Hush theory. The thiophene group attached to the macrocycle L2in these complexes may serve as a precursor to conducting polythiophene-based hybrid materials incorporating redox active transition metal ions. [ABSTRACT FROM AUTHOR]

A chemosensor array comprising 45 off-the-shelf colorimetric dyes, dubbed the Singapore Tongue (SGT), that is capable of discriminating different brands of bottled water and waters of different geographical attribute is described. Twelve kinds of bottled waters were tested by the SGT, and changes of absorbance spectra were analyzed by unsupervised classification methods to validate the SGT system for water analysis. All 12 bottled waters were discriminated at 1 × concentration, and SGT could distinguish the identity of samples of the waters diluted up to 100 times, except distilled waters. Following the study of 63 tap waters in different mass rapid transit stations in Singapore, two distinct clusters were observed from a principal component analysis plot, which correspond to the origin of the tap water. The successful discrimination and identification of in this study demonstrates the practical application of the SGT as a simple tool for water analysis. [ABSTRACT FROM AUTHOR]

The coordination chemistry of three bridging doubly-tridentate ligands, including the known compound 3,6-bis(di-2-pyridylmethyl)pyridazine (1), which is structurally similar to 1,4-bis(di-2-pyridylmethyl)phthalazine (2), and two pyrimidine-linked compounds 4,6-bis(di-2-pyridylmethyl)pyrimidine (3), and 4,6-bis(di-2-pyridylamino)pyrimidine (4), was investigated with FeII, NiII, and PdIImetal salts. Ligands 3 and 4 were synthesized in one-pot reactions from easily obtained starting materials; compound 3 was synthesized from di-2-pyridylmethane and 4,6-diiodopyrimidine in 48% yield, while ligand 4 was prepared by reacting di-2-pyridylamine with 4,6-dichloropyrimidine in 27% yield. During the synthesis of 4, an additional compound, 4-chloro-6-(di-2-pyridylamino)pyrimidine (5), with only one tridentate binding site was obtained in 30% yield. Reactions of 1, 3, and 4 with FeIIor NiIIsalts gave two types of complexes, either discrete M2L or M2L2assemblies. The PdIIcomplexes obtained were also characterized as discrete M2L complexes. The compounds were characterized by a combination of NMR and IR spectroscopy, microanalysis and X-ray crystallography. Noticeable differences in the structures obtained for NiIIcoordination complexes with the carbon-linked (3) and nitrogen-linked (4) ligands were observed, whereby the nitrogen linker adopted a trigonal planar geometry and prevented tridentate facial coordination of the octahedral metal centres. The magnetic properties of dinuclear FeIIcomplexes of 1 were examined to see if they showed spin-crossover effects, a feature recently observed by others in other dinuclear helicate complexes, but the complexes remained high-spin at all temperatures between 300 and 2 K. [ABSTRACT FROM AUTHOR]

The Hawaiian Islands experience damaging wildfires on a yearly basis. Soil moisture or lack thereof influences the amount and flammability of vegetation. Incorporating daily maximum temperatures and daily rainfall amounts, the Keetch-Byram Drought Index (KBDI) estimates the amount of soil moisture by tracking daily maximum temperatures and rainfall. A previous study found a strong link between the KBDI and total area burned on the four main Hawaiian Islands. The present paper further examines the natural variability of the KBDI. The times of year at which the KBDI is highest, representing the highest fire danger, are found at each of the 27 stations on the island chain. Spectral analysis is applied to investigate the variability of the KBDI on longer time scales. Windward and leeward stations are shown to have different sensitivities to large-scale climatic fluctuations. An El Niño signal displays a strong relationship with leeward stations, when examined with a band-pass filter and with a composite of standardized anomalies. Departure patterns of atmospheric circulations and sea surface temperatures over the North Pacific are investigated for composites of extremely high KBDI values when fire risk is high. The winter, spring, and fall show anomalous surface anticyclonic circulations, surface divergence, and subsidence over the islands for the upper quartile of KBDI. The winter, spring, and fall composites of equatorial sea surface temperatures for the upper quartile of KBDI are investigated for possible links to atmospheric circulations. These analyses are an effort to allow fire managers some lead time in predicting future fire risks. [ABSTRACT FROM AUTHOR]

Chaetoviridins E (1) and B (2) are antibiotic active components isolated from the mycelial extract of an elicited laboratory-cultured coprophilous fungus, Chaetomiumsp. obtained from the scat of an emu. The structure of chaetoviridin E was determined to be diastereomeric with the known compound chaetoviridin A, whereas a structure revision of chaetoviridins B and D (10) is proposed, reassigning them to be bicyclic lactol-lactones. The structures of chaetoviridins B and E were determined by detailed spectroscopic analysis, while the revision of chaetoviridin D is through analogy. [ABSTRACT FROM AUTHOR]

To explore the effects of a co-ligand on the construction of mixed-ligand metal–organic frameworks (MOFs), two new triazole-based complexes with a flexible dicarboxylate as a co-ligand, {[Zn4(trz)4(gt)2(H2O)2](H2O)2}n1 and {[Cd2(trz)2(gt)(H2O)2](H2O)4}n2 (Htrz = 1,2,4-triazole; H2gt = glutaric acid), were synthesized and their structures were fully characterized by elemental analyses, IR spectroscopy, and single-crystal X-ray crystallography. Their thermal stability and luminescence emissions were further investigated to establish their structure–property relationship. Crystal structure determination showed that 1 is a neutral two-dimensional pillared-bilayer network consisting of 14-membered hydrophobic channels, whereas 2 is an infinite three-dimensional framework constructed from tetranuclear [Cd4(trz)4]4+subunits. Interestingly, the overall structure of both MOFs can be solely supported by ZnII/CdIIand trz anions, and were further consolidated by the introduction of a flexible gt co-ligand. In addition, the carboxylate groups in the co-ligand can also serve as a weak O–H···O hydrogen-bond acceptor to capture guest water molecules. The synchronous weight-loss behaviour of trz and gt anions presented by thermogravometric curves suggest their cooperative contributions to the thermal stability of the MOFs. In contrast, the fluorescence emissions of two complexes are significantly dominated by the core trz ligand, rather than the gt co-ligand and metal ions. [ABSTRACT FROM AUTHOR]

2-Octylsuccinic acid and its copolyanhydrides with sebacic acid have been synthesized by melt polycondensation, and were characterized by Fourier transform infrared spectroscopy, 1H NMR, gel permeation chromatography, differential scanning calorimetry, and thermal gravimetric analysis. In vitro studies showed that all copolymers are degradable in phosphate buffer at 37°C. The release profiles of the hydrophilic model drug ciprofloxacin hydrochloride follow first-order release kinetics. [ABSTRACT FROM AUTHOR]

Exudates from six species of the genus Eucalyptus and one of the genus Corymbia (formerly Eucalyptus), from the family Myrtaceae, have been characterized by solid-state 13C and solution 1H NMR spectroscopy for the first time. Although these eucalypt kinos, as these exudates often are called, resemble resin (terpenoid) and gum (carbohydrate) exudates in physical appearance, their NMR spectra are dramatically different. In addition to lacking the characteristic terpene saturated resonances, they exhibit strong unsaturated resonances, which are weak for resins and absent for gums. We additionally report that exudates from genera of several other families of flowering plants (Amyris, Centrolobium, Guaiacum, Liquidambar, and Prosopis) also exhibit part or all of this kino spectroscopic signature. [ABSTRACT FROM AUTHOR]

The chain-length dependence of the termination rate coefficient, kt, in methyl acrylate (MA) and dodecyl acrylate (DA) radical polymerization has been determined via the single pulse pulsed-laser polymerization near-infrared reversible addition?fragmentation chain transfer (SP-PLP-NIR-RAFT) technique. Polymerization is induced by a laser SP and the resulting decay in monomer concentration, cM, is monitored via NIR spectroscopy with a time resolution of microseconds. A RAFT agent ensures the correlation of radical chain length and monomer-to-polymer conversion. The obtained rate coefficients for termination of two radicals of approximately the same chain length, i, are represented by power-law expressions, kt(i,i) ? i??. For both monomers, composite model behaviour of kt(i,i) showing two distinct chain length regimes is observed. The exponent ?s referring to short chain lengths is close to unity, whereas the exponent ?l, which characterizes the chain-length dependency of large radicals, is slightly above the theoretical value for coiled chain-end radicals. The crossover chain length, ic, which separates the two regions, decreases from MA (ic = 30) to DA (ic = 20). The results for MA and DA are consistent with earlier data reported for butyl acrylate. There appears to be a correlation of ?s and ic with chain flexibility. [ABSTRACT FROM AUTHOR]

The determination of nanoparticle wettability is an area of great practical importance to materials science and engineering fields. There has been some recent interest in using spectroscopic analysis to indirectly categorize behaviour of monolayers, using the reflective and refractive properties of immersed particles. A method is developed here to calculate specific contact information for nanoparticles at an air?water interface, using single wavelength ellipsometry. A two-layer model is used that considers the refractive index of the immersed and non-immersed particle portions. Pressure€“area isotherms and Brewster angle images were used to confirm and categorize the nature of a packed monolayer, and ? and ? measurements taken of the interface. Immersion thickness was calculated and related to an equilibrium contact angle, and combined thickness data for the two layers was successfully related to the diameter of the particles. [ABSTRACT FROM AUTHOR]

X-Ray absorption near-edge structure (XANES) spectroscopy was used to monitor the oxidation state of cobalt following treatment of CoIII complexes with reducing agents such as ascorbate and cysteine. It was established that the XANES spectra of mixtures of CoII and CoIII complexes can be used to calculate proportions of the two oxidation states by monitoring the height of the Co K-edge. The relationships developed were used to estimate proportions of each complex in solutions of CoIII complexes treated with reducing agents. [ABSTRACT FROM AUTHOR]

A hydrogen bonded network of composition Zn8(C4O7)4(H2O)12hydrate was shown to undergo a single crystal to single crystal exchange process when crystals are immersed in a concentrated aqueous solution of Ni(ii). In the exchange process, half of the zinc(ii) centres are replaced by nickel(ii) centres. The process of metal ion exchange was monitored using IR spectroscopy. Crystal structures of the transformed crystal and the product generated from a direct synthetic approach are presented. [ABSTRACT FROM AUTHOR]

Dihydroazulene (DHA)-vinylheptafulvene (VHF) photoswitches have attracted attention as potentially useful components in molecular electronics. The π-conjugated dihydroazulene system is a rigid structure and can be strategically functionalised to place handles for further elaboration. Here we show that alkyne-functionalised dihydroazulenes can be subjected to copper and ruthenium catalysed azide-alkyne cycloadditions (CuAAC and RuAAC) with tolylazide, furnishing 1,4- and 1,5-disubstituted triazoles. The rates of ring-closure of the corresponding vinylheptafulvenes were compared with those of reference systems, which allowed determination of Hammett substituent constants (meta and para) for N-tolyl-substituted 1,2,3-triazoles. [ABSTRACT FROM AUTHOR]

Absorptions commencing at 602.6 nm are detected following deposition of mass-selected C[sub 7]H[sub 4] [sup +] in a 6 K neon matrix produced from a 1 : 1 mixture of diacetylene and propyne in an ion source. The 602.6 nm system, and a weaker one near 421.1 nm, are assigned to the A [sup 2]E ← X [sup 2]E and B [sup 2]E ← X [sup 2]E electronic transitions of methyltriacetylene cation (C [sub 3V] symmetry), based on mass-selection, spectroscopic analysis of the vibrational structure, and the excitation energies calculated with CASPT2. Structured fluorescence is detected in the 600-760 nm range upon laser excitation at wavelengths of the CH[sub 3]C[sub 6]H[sup +] absorptions. The vibrational bands observed in the absorption and fluorescence spectra are assigned with the aid of calculated frequencies of the totally symmetric (a[sub 1]) vibrations of methyltriacetylene cation. [ABSTRACT FROM AUTHOR]

A study of the room-temperature ionic liquid N-methyl-N-ethylpyrrolidinium dicyanamide by dielectric relaxation spectroscopy over the frequency range 0.2 GHz ? ? ? 89 GHz has revealed that, in addition to the already known lower frequency processes, there is a broad featureless dielectric loss at higher frequencies. The latter is probably due to the translational (oscillatory) motions of the dipolar ions of the IL relative to each other, with additional contributions from their fast rotation. [ABSTRACT FROM AUTHOR]

Non-isothermal H[sub 2] plasma reduction of supported silver nitrate or palladium acetate leads to the formation of metallic films. This method benefits from being able to coat heat-sensitive substrates, as well as complex shaped objects, without the requirement for large amounts of solvent or complex chemical synthesis. X-ray diffraction, X-ray photoelectron spectroscopy, attenuated total reflectance-FTIR spectroscopy, and optical microscopy have been used to follow the various stages of this low temperature metallization technique. Non-isothermal (cold) H[sub 2] plasma reduction of supported silver nitrate or palladium acetate leads to the formation of metallic films. [ABSTRACT FROM AUTHOR]

The article discusses anion photoelectron spectrum of the bromide-carbon monoxide complex. It has been informed that the spectrum shows transitions between anion and neutral van der Waals complexes. It has been informed that details on the electronic, vibrational and rotational energy levels are being provided through spectroscopy and theoretical investigation of gas phase ion-molecule complexes and clusters.

The article offers information on topics discussed at the symposium Frontiers in Optical Bio-Imaging and Microscopy which took place at the Suntec Conference Centre in Singapore from June 26-July1, 2011. Several papers related to the topics of optical design, biological imaging, spectroscopy, and photochemistry were discussed at the symposium. Several college teachers attended the event which include Colin Sheppard, Brahim Lounis, and Jonathan Hobley. [ABSTRACT FROM AUTHOR]

Plant phenotyping is an emerging discipline in plant biology. Quantitative measurements of functional and structural traits help to better understand gene-environment interactions and support breeding for improved resource use efficiency of important crops such as bean (Phaseolus vulgaris L.). Here we provide an overview of state-of-the-art phenotyping approaches addressing three aspects of resource use efficiency in plants: belowground roots, aboveground shoots and transport/allocation processes. We demonstrate the capacity of high-precision methods to measure plant function or structural traits non-invasively, stating examples wherever possible. Ideally, high-precision methods are complemented by fast and high-throughput technologies. High-throughput phenotyping can be applied in the laboratory using automated data acquisition, as well as in the field, where imaging spectroscopy opens a new path to understand plant function non-invasively. For example, we demonstrate how magnetic resonance imaging (MRI) can resolve root structure and separate root systems under resource competition, how automated fluorescence imaging (PAM fluorometry) in combination with automated shape detection allows for high-throughput screening of photosynthetic traits and how imaging spectrometers can be used to quantify pigment concentration, sun-induced fluorescence and potentially photosynthetic quantum yield. We propose that these phenotyping techniques, combined with mechanistic knowledge on plant structure-function relationships, will open new research directions in whole-plant ecophysiology and may assist breeding for varieties with enhanced resource use efficiency varieties. [ABSTRACT FROM AUTHOR]

Flowerlike Ni microcrystals composed of star-shaped Ni nanorods with a diameter of ~200 nm were fabricated by a facile chemical reduction process, in which ethylenediamine tetraacetic acid sodium (EDTA) was used as complexant to assist in the formation of the flowery shape of the sample. The products were characterized by X-ray diffractometer, scanning electron microscopy, energy-dispersive X-ray spectroscopy and superconducting quantum interference device magnetometer. Scanning electron microscopy images indicated the typical size of the flowery Ni microcrystals was 2-3 µm and the length of the star-shaped Ni nanorods was in the hundreds of nanometers up to micron scale. The X-ray diffraction pattern showed the Ni microcrystals were present in the face-centred cubic phase and magnetic measurement results demonstrated the greatly enhanced coercivity of the sample (168.5 Oe) at room temperature. Based on the evolution of the structure and the morphology of products with increasing reaction time, a possible formation mechanism was proposed to illustrate the growth of the flower-like Ni architecture. [ABSTRACT FROM AUTHOR]

Molecules bearing polyphenylphenyl dendrons show great potential for applications in organic light-emitting diodes. In this paper, quantum-chemical calculations have been applied to investigate the structural and electronic properties of typical molecules bearing polyphenylphenyl dendrons, 2-(2′,3′,4′,5′-tetraphenyl)phenyl-5-(p-N,N-dimethyl)phenyl pyridine (A), 1-(2′,3′,4′,5′-tetraphenyl)phenyl-4-(p-N,N-dimethyl)phenyl benzene (B), 2-(2′,3′,4′,5′-tetraphenyl)phenyl-5-(p-N,N-dimethyl)phenyl thiophene (C), 1-(2′,3′,4′,5′-tetraphenyl)phenyl-2,5-dimethoxy-4-(p-N,N-dimethyl)phenyl benzene (D), and 2-(2′,3′,4′,5′-tetraphenyl)phenyl-5-(p-N,N-dimethyl)phenyl furan (E). The geometrical and electronic structures in the ground state and lowest singlet excited states have been optimized by B3LYP/6-31G(d) and TD-B3LYP/6-31G(d) methods, respectively. The important parameters, including ionization potential (IP), electron affinity, the reorganization energies (λ), hole extraction potential, and electron extraction potential, first lowest singlet excitation energies, maximum absorption and emission wavelengths are also systematically investigated. The result implied that the HOMO, energy gaps, and IP are affected by the central aromatic ring in the order of phenylene>pyrryl> 2,5-dimethoxyphenylene>thienyl>furyl. The solvent effects on absorption and emission spectra were further examined using the polarizable continuum model. [ABSTRACT FROM AUTHOR]

Quantum-chemical calculations employing different theoretical methods and basis sets have been performed on borabenzene (C5H5B) as well as on its adducts to dinitrogen (N2) and the rare gases Ne, Ar, and Kr. In agreement with previous calculations, the ground state of borabenzene was found to be a planar singlet with six electrons in molecular orbitals of π symmetry and a wide C-B-C bond angle (142.2°). Depending on the method (PUMP2, SAC-CI, CASPT2(8,8)), the lowest triplet state was found to be 28 to 46kcalmol-1 (1kcalmol-1=4.186kJmol-1) higher in energy. The energies associated with the formation of the adducts with N2, Ne, Ar, and Kr were calculated as -14.9, -0.5, -1.4, and -3.5kcalmol-1 respectively. Our calculated spectrum of the normal modes as well as the electronic excitation spectrum of the N2 adduct reproduce qualitatively the characteristic features of the IR and the UV-vis spectra described by experimentalists. The corresponding calculated spectra (normal modes, UV-vis) of the rare gas adducts were found to be very similar to those of free borabenzene. [ABSTRACT FROM AUTHOR]