Bisresorcinols and arbutin derivatives from Grevillea banksii R. Br

This work is part of a series of chemical investigations of the genus Grevillea. Two new arbutin derivatives, seven new bisresorcinols, including a mixture of two isomers, three known flavonol glycosides, and four known resorcinols, including a mixture of two homologous compounds, were isolated from the ethyl acetate extract of the leaves and methanol extract of the stems of Grevillea banksii. The new compounds were identified, on the basis of spectroscopic data, as 6'-O-(3-(2(hydroxymethyl)acryloyloxy)-2-methylpropanoyl)arbutin (1), 6'-O-(2-methylacryloyl)arbutin (2), 5,5'-(4(Z)-dodecen-1,12diyl)bisresorcinol (6), 2'-methyl-5,5'-(4(Z)-tetradecen-1,14-diyl)bisresorcinol (8), 2,2'-di(4-hydroxyprenyl)-5,5'-(6(Z)-tetradecen-1,14-diyl)bisresorcinol (9), 2-(4-acetoxyprenyl)-2'-(4-hydroxyprenyl) 5,5'-(6(Z)-tetradecen-1,14-diyl)bisresorcinol (10), 2-(4-acetoxyprenyl)-2'-(4-hydroxyprenyl)5,5'-(8(Z)-tetradecen-l,14-diyl)bisresorcinol (11), 5,5'-(10(Z)-tetradecen-1-on-diyl)bisresorcinol (12) and 5,5'-(4(Z)-tetradecen-1-on-diyl)bisresorcinol (13).

Effect of microwave radiation on seed mortality of rubber vine (Cryptostegia grandiflora R.Br.), parthenium (Parthenium hysterophorous L.) and bellyache bush (Jatropha gossypiifolia L.)

A trial was undertaken to evaluate the effect of microwaves on seed mortality of three weed species. Seeds of rubber vine (Cryptostegia grandiflora R.Br.), parthenium (Parthenium hysterophorous L.) and bellyache bush (Jatropha gossypiifolia L.) were buried at six depths (0, 2.5, 5, 10, 20 and 40 cm) in coarse sand maintained at one of two moisture levels, oven dry or wet (field capacity), and then subjected to one of five microwave radiation durations of (0, 2, 4, 8 and 16 min). Significant interactions between soil moisture level, microwave radiation duration, seed burial depth and species were detected for mortality of seeds of all three species. Maximum seed mortality of rubber vine (88%), parthenium (67%) and bellyache bush (94%) occurred in wet soil irradiated for 16 min. Maximum seed mortality of rubber vine and bellyache bush seeds occurred in seeds buried at 2.5 cm depth whereas that of parthenium occurred in seeds buried at 10 cm depth. Maximum soil temperatures of 114.1 and 87.5°C in dry and wet soil respectively occurred at 2.5 cm depth following 16 min irradiation. Irrespective of the greater soil temperatures recorded in dry soil, irradiating seeds in wet soil generally increased seed mortality 2.9-fold compared with dry soil. Moisture content of wet soil averaged 5.7% compared with 0.1% for dry soil. Results suggest that microwave radiation has the potential to kill seeds located in the soil seed bank. However, many factors, including weed species susceptibility, determine the effectiveness of microwave radiation on buried seeds. Microwave radiation may be an alternative to conventional methods at rapidly depleting soil seed banks in the field, particularly in relatively wet soils that contain long lived weed seeds.

An infrared spectroscopic study of the incommensurate transitions and related phase changes in K2Pb[Cu(NO2)6] and [N(CH3)4]2MX4 (M = Mn, Co, Cu or Zn and X = Cl or Br)

K2Pb[Cu(NO2)6] and [N(CH3)4]2MX4 (M = Mn, Co, Cu or Zn and X = Cl or Br) undergo phase transitions which involve incommensurate phases. The transitions have been investigated by examining the changes in the NO2 and CH3 vibration bands in the i.r. spectra. Splitting and broadening of some of the bands across the incommensurate transitions are discussed in the context of geometrical restrictions in the incommensurate phases. The phase transitions have also been characterized using differential scanning calorimetry.

Role of Mn impurity in the deterioration of ZnS:Cu, Br electroluminescent phosphors

ZnS:Cu, Br powder EL phosphors showed 6-line EPR signal at 25°C whose intensity increases with Cu content and on annealing in Zn-vapour. The signal arises from native Mn impurity. The starting material does not show any EPR signal since Mn2+ acts as an affinity potential well for a hole in ZnS, forming Mn3+ - a chemically uncommon situation in sulfides. In doped ZnS, holes are trapped at Cu such that Mn2+ persists. Deterioration of EL brightness is accompanied by the decrease in EPR signal intensity due to field assisted hole transference to Mn2+. Intentional addition of Mn in ZnS:Cu, Br decreases the brightness and shortens life time. Stable phosphors require ZnS with Mn content less than 1014 cm−3.

First observation of the decay Bs --> Ds K and measurement of the ratio of branching fractions Br(Bs --> DsK)/Br(Bs --> Ds pi)

A combined mass and particle identification fit is used to make the first observation of the decay Bs --> Ds K and measure the branching fraction of Bs --> Ds K relative to Bs --> Ds pi. This analysis uses 1.2 fb^-1 integrated luminosity of pbar-p collisions at sqrt(s) = 1.96 TeV collected with the CDF II detector at the Fermilab Tevatron collider. We observe a Bs --> Ds K signal with a statistical significance of 8.1 sigma and measure Br(Bs --> Ds K)/Br(Bs --> Ds pi) = 0.097 +- 0.018(stat) +- 0.009(sys).

Transport and magnetic properties of conducting polyaniline doped with BX3 (X=F, Cl, and Br)

We report transport and magnetic properties of a different class of highly conducting polyaniline, doped with boron trihalides BX3 (X=F, Cl, and Br). In order to understand the transport mechanism we analyze the temperature dependence of resistivity of a large number of samples, made by pelletizing doped polyaniline powder and by doping films of polyaniline. We find that the charge transport in this class of conducting polyaniline is driven by the charging-energy limited transport of charge carriers, in contrast to the quasi-one-dimensional variable range hopping conduction prevalent in conventional proton-doped polyaniline samples. Magnetic susceptibility provides further insight into the unusually high intrinsic conductivity behavior.

Synthesis, Characterization and Structure of (N2H5)3MnX5 (X = Cl and Br)

Two new hydrazinium complexes of manganese, (N2H5)3MnX5 (X = Cl and Br), have been prepared and characterized by analysis, infrared and visible spectra. The single crystal X-ray structure of the chloride complex has been determined. Only one of the three N2H+5 cations is coordinated to the metal. In the anion, [Mn(N2H5)Cl5]2-, the coordination polyhedron around the manganese atom is a slightly distorted octahedron.

Pulsed NMR study of molecular motions and phase transitions in [N(CH3)4]PbX3 (X=Cl, Br, I)

Proton spin—lattice relaxation time (T1) is measured in [N(CH3)4]PbX3 (X=Cl, Br, I) from 300-77 K at 9.75 MHz. All the compounds show discontinuous changes in T1 values (at 256, 270 and 277 K, respectively), indicating phase transitions. Single T1 minimum is observed in all the cases and the T1 variation is explained in terms of [N(CH3)4] and CH3 group dynamics. The activation energy Eα decreases from chloride to iodide (from 4 to 2 kcal/mol). In bromide and iodide, T1 is found to decrease with increase in temperature at higher temperatures, indicating the presence of spin—rotation interaction.

Role of Hetero-Halogen (F center dot center dot center dot X, X = Cl, Br, and I) or Homo-Halogen (X center dot center dot center dot X, X = F, Cl, Br, and I) Interactions in Substituted Benzanilides

A series of halogen-substituted benzanilides have been synthesized and characterized, and crystallization studies directed toward generation of polymorphs have been performed to delineate the importance of interactions involving halogens. The effect of halogen substitution on the molecular conformation and supramolecular packing has been investigated. The N-H center dot center dot center dot O H-bond is a key structure-directing element acting in conjunction with C-H center dot center dot center dot O and C-H center dot center dot center dot pi interactions. In addition, it is of importance to note that organic fluorine prefers Type I F center dot center dot center dot F contacts, whereas Cl, Br, and I prefer Type II contacts. Hetero-halogen center dot center dot center dot halogen interactions on the other hand are predominately of Type II geometry, and this is due to the greater polarizability of the electron density associated with the heavier halogens. It is of importance to evaluate the contributing role of these interactions in crystal structure packing and the co-operativity associated with such interactions in the solid state.

Theory of coexisting charge and spin-density waves in (TMTTF)(2)Br, (TMTSF)(2)PF6 and alpha-(BEDT-TTF)(2)MHg(SCN)(4)

We discuss a recently formulated microscopic theory of the unusual coexistence of spin density waves (SDWs) and charge density waves (CDWs) that has been seen in recent experiments on (TMTTF)2Br, (TMTSF)2PF6 and α-(BEDT-TTF)2MHg(SCN)4.

Theory of coexisting charge and spin-density waves in (TMTTF)(2)Br, (TMTSF)(2)PF6, and alpha-(BEDT-TTF)(2)MHg(SCN)(4)

Recent experiments indicate that the spin-density waves (SDWs) in (TMTTF)(2)Br, (TMTSF)(2)PF6, and alpha-(BEDT-TTF)(2)MHg(SCN)(4) are highly unconventional and coexist with charge-density waves (CDWs). We present a microscopic theory of this unusual CDW-SDW coexistence. A complete understanding requires the explicit inclusion of strong Coulomb interactions, lattice discreteness, the anisotropic two-dimensional nature of the lattice, and the correct hand filling within the starting Hamiltonian. [S0031-9007(99)08498-7].