Synthesis and characterization of binary and heterobimetallic complexes of dithiofuroate with 3d-metal ions

New complexes [M(dtf)2] (M=MnII or CuII), Cr(dtf)3 and V(dtf)4 (dtf=dithiofuroate) and heterobimetallic complexes M[Cd(dtf)4] (M=VO2+, MnII, FeII, CoII, NiII or ZnII) have been prepared in H2O−EtOH and characterized by elemental analyses, magnetic susceptibility measurements and spectroscopic studies. The known complexes Fe(dtf)3, Co(dtf)3, Ni(dtf)2, and Zn(dtf)2 have been screened towards the bacteria Pseudomonas spergillus and Bacillus spergillus. In vitro results of the binary complexes on P-815 (murine mastocytoma) indicate that these complexes show significant inhibition of [3H]thymidine and [3H]uridine incorporation in DNA and RNA in the tumour cells. This revised version was published online in June 2006 with corrections to the Cover Date.     

Systematic trends in the line strengths of E1 transitions in the carbon isoelectronic sequence

Line strengthsS for the dipole allowed transitions within then=2 complex of the carbon isoelectronic sequence have been fitted in the formZ ² S=A+B/(Z–C), whereZ is the nuclear charge of a particular ion. The constantsA,B andC are determined by using a non-linear least square method. The data forS is taken from the configuration interaction calculations which included internal, semi-internal and all external type correlations for ions in the rangeZ=8–26. It is shown that the values ofA obtained from the fit for all the transitions are in excellent accord with the ab-initio values obtained in the hydrogenic limitZ provided near degeneracy effects are included.     

Uranyl ion luminescence quenching with benzene derivatives and related compounds. Linear free energy relationship

Irradiation of uranyl ion with light of wavelength =345 nm to singlet state, through vibrational relaxation populates the lowest excited triplet state from where it emits luminescence emission at 486, 506, 535 nm. Elongation and weakening of uranium-oxygen multiple bonds is evident from the lower stretching frequency (701.15 cm^–1) in the excited state relative to the ground state (942.5 cm^–1). Series of aromatic molecules including benzene derivatives, aromatic hydrocarbons and heterocyclic molecules very efficiently quench uranyl ion luminescence through nonradiative donor-acceptor complex formation. Increasing inductive effect, resonance phenomena and extension of aromatic -electron cloud determine the order of Stern-Volmer constant to measure their quenching action.     

Simultaneous First Derivative Spectrophotometric Determination of Palladium and Nickel Using 2-(2-Thiazolylazo)-5-Dimethylaminobenzoic Acid as an Analytical Reagent

 A simple, rapid, selective, sensitive and economical method has been developed for the simultaneous determination of trace amounts of palladium and nickel in aqueous methanolic medium using 2-(2-thiazolylazo)-5-dimethylam inobenzoic acid as an analytical reagent by first derivative spectrophotometr y. Palladium is determined by measuring base to peak distance at λ=695.0 nm while nickel is estimated by zero crossing method in the mixture. The linearity is maintained between 0.12–1.75 μg mL⁻¹ for palladium and 0.07–1.60 μg mL⁻¹ for nickel in the pH range 2.8–7.2 and 3.4–8.8 respectively. Seven replicate determinations of 1.0 μ g mL⁻¹ of palladium and 0.8 μg mL⁻¹ of nickel in a mixture give a mean signal height of 0.391 for Pd and 0.541 for Ni with relative standard deviations of 0.9% and 1.2%, respectively. The sensitivity of the proposed method is 0.391 (dA/dλ)/(μg mL⁻¹) for palladium and 0.685 (dA/dλ)/(μg mL⁻¹) for nickel. Various parameters have been optimised for the simultaneous determination of palladium and nickel in various complex samples. Received March 30, 1999. Revision November 25, 1999.     

Physical controls on directed virus assembly at nanoscale chemical templates

Viruses are attractive building blocks for nanoscale heterostructures, but little is understood about the physical principles governing their directed assembly. In situ force microscopy was used to investigate organization of Cowpea Mosaic Virus engineered to bind specifically and reversibly at nanoscale chemical templates with sub-30 nm features. Morphological evolution and assembly kinetics were measured as virus flux and inter-viral potential were varied. The resulting morphologies were similar to those of atomic-scale epitaxial systems, but the underlying thermodynamics was analogous to that of colloidal systems in confined geometries. The 1D templates biased the location of initial cluster formation, introduced asymmetric sticking probabilities, and drove 1D and 2D condensation at sub-critical volume fractions. The growth kinetics followed a t(1/2) law controlled by the slow diffusion of viruses. The ability of poly(ethylene glycol) (PEG) to induce the lateral expansion of virus clusters away from the 1D templates suggests a significant role for weak interactions.     

meso-Aryl triphyrin(2.1.1)

Synthesis, spectral, and single-crystal X-ray structural analysis of meso-aryl triphyrin(2.1.1) featuring three pyrrole rings and four meso-aryl rings are described. The title compound represents the first example of a ring-contractedmeso-aryl β-unsubstituted free-base triphyrin containing only pyrrole rings reported to date and generates 2-D supramolecular assembly in the solid state.     

Monitoring the emission of volatile organic compounds from flowers of Jasminum sambac using solid-phase micro-extraction fibers and gas chromatography with mass spectrometry detection

Solid-phase micro-extraction (SPME) was studied as a solvent free alternative method for the extraction and characterization of volatile compounds in intact and plucked flowers of Jasminum sambac at different day time intervals using gas chromatography (GC-FID) and gas chromatography-quadrupole mass spectrometry. The analytes identified included alcohols, esters, phenolic compounds, and terpenoids. The main constituents identified in the flower aroma using different fibers were cis-3-hexenyl acetate, (E)-beta-ocimene, linalool, benzyl acetate, and (E,E)-alpha-farnesene. The benzyl acetate proportion decreased from morning to afternoon and then increased in evening collections. PDMS fiber showed a high proportion of (E,E)-alpha-farnesene in jasmine floral aroma. Among other constituents identified, cis-3-hexenyl acetate, linalool, and benzyl acetate were major aroma contributors in plucked and living flowers extracts using PDMS/DVB, Carboxen/PDMS, and DVB/Carboxen/PDMS fibers. PDMS/DVB recorded the highest emission for benzyl acetate while the (E)-beta-ocimene proportion was highest in DVB/Carboxen/PDMS when compared with the rest. The highest linalool content, with increasing proportion from morning to noon, was found using mixed coating fibers. Almost negligible volatile adsorption was recorded for the polyacrylate fiber for intact flower aroma, whereas it was most effective for benzyl acetate, followed by indole under plucked conditions. Moreover, the highest amounts extracted, evaluated from the sum of peak areas, were achieved using Carboxen/PDMS, and DVB/Carboxen/PDMS. Introduction of a rapid, and solvent free SPME method for the analysis of multicomponent volatiles can be successfully employed to monitor the extraction and characterization of flower aroma constituents.     

Isothermal crystallization kinetics of poly(trimethylene terephthalate)/multiwall carbon nanotubes composites

The isothermal crystallization kinetics of poly(trimethylene terephthalate) (PTT) in the presence of varying amounts of multiwall carbon nanotubes (MWCNT) have been investigated using differential scanning calorimetry (DSC) and analyzed using Avrami and secondary nucleation theory. Polarized light microscopy (PLM) was used to study the crystal morphology of PTT/MWCNT composites. The results showed that the presence of MWCNTs in PTT acted as an effective nucleating agents and lead to the spherulitic morphology. The decrease in the spherulites size on MWCNT addition was observed by polarized light microscopy. Using values of transport parameters ( $ U* = 1500{\text{ cal mol}}^{ - 1} , \, \Updelta T =T_{\text{g}} - 30\, $ °C) together with experimentally determined values of equilibrium melting temperature [ $ T^{\text{o}}_{\text{m}} $ (245.2 °C)] and glass transition temperature [ $ T_{\text{g}} $ (45 °C)], the nucleation parameter, $ K_{\text{g}} $ and $ \sigma_{\text{e}} $ were determined for PTT and PTT/MWCNT composites according to Lauritzen–Hoffman theory. The decrease in the values of these parameters on MWCNT addition is in agreement with the fact that the rate of crystallization of PTT increased in the presence of MWCNTs.     

Analytical modeling and simulation of subthreshold behavior in nanoscale dual material gate AlGaN/GaN HEMT

A two-dimensional (2-D) analytical model for a Dual Material Gate (DMG) AlGaN/GaN High Electron Mobility Transistor (HEMT) has been developed to demonstrate the unique attributes of this device structure in suppressing short channel effects (SCEs). The model accurately predicts the channel potential, electric field variation along the channel, and sub-threshold drain current, taking into account the effect of lengths of the two gate metals, their work functions, barrier layer thicknesses, and applied drain biases. It is seen that the SCEs and hot carrier effects in DMG AlGaN/GaN HEMT are suppressed due to the work function difference of the two metal gates, thereby screening the drain potential variations by the gate near the drain. Besides, a more uniform electric field along the channel leads to improved carrier transport efficiency. The accuracy of the results obtained from our analytical model has been verified using ATLAS device simulations.