Deposition of SiOx Films from Hexamethyldisiloxane/Oxygen Radiofrequency Glow Discharges: Process Optimization by Plasma Diagnostics

Optical emission and Fourier transform infrared absorption diagnostics have been carried out in hexamethyldisiloxane/oxygen RF discharges for studying the effects of the feed composition and the power on the deposition of SiO₂—like thin films. Ex situ FTIR absorption has been utilized to monitor organic moieties and silanol groups in the film. It is shown that carbon-free films can be obtained by highly diluting the monomer in oxygen, while medium-to-high power is necessary to abate silanol groups. These two conditions represent the optimization criterion to obtain excellent barrier films for food packaging applications.     

Solution structure of folic acid. Molecular mechanics and NMR investigation

The structure of folic acid in solution was investigated by nuclear magnetic resonance (NMR) and theoretical calculations. Dynamical information and geometrical constraints were obtained by carbon-13 relaxation study, homo-nuclear NOESY spectra and hetero-nuclear 1H-13C NOE experiments. This set of experimental data was used for the molecular mechanics and molecular dynamic calculations. The accuracy of the final structure was established by the R(NMR) factor, which was calculated comparing the experimental NOESY cross-peaks intensities and the corresponding values simulated by using the complete relaxation matrix analysis (CORMA) approach.     

Concise and stereocontrolled synthesis of pseudo-C2-symmetric diamino alcohols and triamines for use in HIV protease inhibitors

A new protocol is described for the stereocontrolled synthesis of pseudo-C(2)-symmetric core units of interest as candidates for HIV protease inhibition. Addition of unbranched and branched organolithium reagents to cyanohydrins from l-phenylalaninal and l-isoleucinal, followed by in situ reduction of the intermediate imines and CHT deprotection under MW irradiation, led to 1,3-diamino alcohols 6a and 8a as the major products in satisfactory to good yields. The first preparation of a previously unreported pseudo-C(2)-symmetric triamino derivative was accomplished expeditiously via high-yielding nitro-Mannich addition of the silylnitronate, from 2-phenyl-1-nitroethane, to the PMP imine derived from l-phenylalaninal. Reduction of the nitro group in the moderately unstable nitro diamine adduct, followed by chromatographic separation of the required diastereoisomer and CHT debenzylation under MW irradiation, led to the 2-PMP-protected triamine 19 isolated as a bis(sulfonamide).     

A vinylene‐linked benzo[1,2‐b:4,5‐b']dithiophene‐2,1,3‐benzothiadiazole low‐bandgap polymer

A new heteroarylene‐vinylene donor–acceptor polymer P(BDT‐V‐BTD) with reduced bandgap has been synthesized and its photophysical, electronic and photovoltaic properties investigated both experimentally and theoretically. The structure of the polymer comprises an unprecedented combination of a strong donor (4,8‐dialkoxy‐benzo[1,2‐b:4,5‐b']dithiophene, BDT), a strong acceptor (2,1,3‐benzothiadiazole, BTD) and a vinylene spacer. The new polymer was obtained by a metal‐catalyzed cross‐coupling Stille reaction and fully characterized by NMR, UV–vis absorption, GPC, TGA, DSC and electrochemistry. Detailed ab initio computations with solvation effects have been performed for the monomer and model oligomers. The electrochemical investigation has ascertained the ambipolar character of the polymer and energetic values of HOMO, LUMO and bandgap matching materials‐design rules for optimized organic photovoltaic devices. The HOMO and LUMO energies are consistently lower than those of previous heteroarylene‐vinylene polymer while the introduction of the vinylene spacer afforded lower bandgaps compared to the analogous system P(BDT‐BTD) with no spacer between the aromatic rings. These superior properties should allow for enhanced photovoltages and photocurrents in photovoltaic devices in combination with PCBM. Preliminary photovoltaic investigation afforded relatively modest power conversion efficiencies of 0.74% (AM 1.5G, 100 mW/cm²), albeit higher than that of previous heteroarylene‐vinylene polymers and comparable to that of P(BDT‐BTD). © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Effect of drying conditions during sample pre-treatment on the determination of polycyclic aromatic hydrocarbons in soils

In the context of the entire analytical process, pre-treatment of soil samples is often inadequately considered although the reliability of the results is definitely compromised if the sample is not properly prepared. In this paper, the effect of drying conditions in soil sample pre-treatment on the determination of polycyclic aromatic hydrocarbons (PAHs) has been studied. A systematic approach has been adopted by varying soil type, drying temperatures and solvent polarity to highlight the effect on the analyte recovery; the relationship between PAH molecular structure and their evaporation process from soils is discussed. Experimental data demonstrate that, concerning temperature-assisted drying procedures, PAHs are divided in two distinct groups: PAHs lighter than pyrene, which are seriously affected by drying temperature; and heavier PAHs that can be considered as non-volatile compounds. For studies involving the analysis of lighter PAHs in environmental samples, working on as-received samples is necessary.     

New Tetracyclic Colchicinoids from the Reaction of N‐Deacetylthiocolchicine and N‐Deacetylcolchicine with Nitrous Acid and tert‐Butyl Nitrite

Reaction of N‐deacetylthiocolchicine ( 3 ) and N‐deacetylcolchicine ( 4 ) with nitrous acid (HONO) furnished the new tetracyclic colchicinoids 5 and 6 , as well as the Demyanov‐rearrangement products 7 and 8 . Starting from 3 , the pyrazole‐containing tetracycle 9 was obtained. The novel compounds were characterized spectroscopically, and an X‐ray crystal‐structure analysis of 5 allowed us to establish the absolute configurations at the stereogenic centers.     

Immobilization of Heparin and Highly-Sulphated Hyaluronic Acid onto Plasma-Treated Polyethylene

Heparin and highly-sulphated hyaluronic acid have been successfully immobilized onto plasma-processed polyethylene via a diamine polyethyleneglycol (PEG) spacer molecule. Two different plasma-processes have been utilized, i.e. a treatment and a deposition process, for providing polyethylene surface with the COOH groups necessary for the immobilization reactions. XPS integrated with derivatization procedures, ATR-FTIR and Water Contact Angle measurements have been carried out for characterizing each modification step: 1) the plasma-process, 2) the immobilization of the spacer molecule and 3) the immobilization of the biomolecules. The thrombin time of the modified surfaces has been measured, and their platelet activation characteristics evaluated. The results indicate a certain nonthrombogenic character of the biomolecule-immobilized polyethylene samples.     

The diphosphate monoanion in the gas phase: a joint mass spectrometric and theoretical study

H(3)P(2)O(7) (-) ions were obtained in an electrospray ion source of a Fourier transform ion cyclotron resonance (ESI/FTICR) mass spectrometer from a CH(3)CN/H(2)O (1:1) pyrophosphoric acid solution and in the ionic source of a triple quadrupole (TQ) mass spectrometer from the chemical ionisation (CI) of pyrophosphoric acid introduced by a thermostatically controlled direct insertion probe. The ions were structurally characterised by mass spectrometric techniques and theoretical calculations. Consistent with collisionally activated dissociation (CAD) mass spectrometric results, theoretical calculations identified the linear diphosphate anion (I) as the most stable isomer on the H(3)P(2)O(7) (-) potential energy surface. The joint application of mass spectrometric techniques and theoretical methods provided information on the dissociative processes of diphosphate anions in the gas phase. Finally, this study provides an insight into the structures and stabilities of the [H(3)PO(4).PO(3)](-), [HP(2)O(6).H(2)O](-) and [H(2)PO(4).HPO(3)](-) clusters and allows the stability and structure of the dimetaphosphate anion, HP(2)O(6) (-), to be investigated at the B3LYP6-31+G* and CCSD(T) levels of theory.     

Synthesis and Reactivity of a Cationic Platinum(II) Alkylidene Complex

Often proposed, hard to catch: The bis(platinacycle) trans-[Pt{P[2,6-(CH(2) )(Me)C(6) H(3) ]iPr(2) }(2) ] experiences α-hydride abstraction by action of Ph(3) C(+) PF(6) (-) to yield a trans-alkyl-alkylidene species. The electrophilicity of its {Pt?CH}(+) unit is demonstrated by ylide formation by reaction with Lewis bases, stepwise hydrogenation, and carbene cross-coupling with N(2) C(H)CO(2) Et.