Porogen approach for the fabrication of plasma-polymerized nanoporous polysiloxane films

Nanoporous polysiloxane films were fabricated by plasma polymerization of hexamethyldisiloxane mixed with cyclohexane under different conditions. The pores were generated through the elimination of carbonaceous aggregates (porogen) by annealing at 600 degrees C. Results of spectroscopic ellipsometry, Fourier transform infrared spectroscopy, and positron annihilation lifetime spectroscopy suggest that not only film porosity but also average pore size depends on the amount of the decomposable porogen. The pore size was controllable in a range between 0.6 and 1.0 nm in radius by proper selection of the substrate temperature and precursor composition.     

Hydrothermal Synthesis and Crystal Structure of a New BariumVanadium Bronze Ba1+xV8O21 with a Tunnel Structure

A barium vanadium bronze Ba_1+xV₈O₂₁ has been hydrothermally synthesized and structurally characterized. Hydrothermal treatment of a suspension of VO₂ powders in Ba(NO₃)₂ solution at 350°C yielded a fibrous brown compound having nonstoichiometric composition Ba_1+xV₈O₂₁ (x=0.13). Single-crystal X-ray diffractometry revealed the monoclinic system C2/m with a=15.144(6), b=3.596(4), c=14.972(3) Å, β=90.08(3)°, and Z=2, with the refinement based on 2021 reflections with I>3σ(I) converged to R=0.054 and R_w=0.046. A new tunnel-type bronze structure was disclosed in which VO₆ octahedra and VO₅ trigonal bipyramids form a V–O framework with a tunnel cavity running along [010]. The Ba atom partially occupies the tunnel site with more than half occupancy of 56.6%, which causes displacement of the Ba atom and further displacement of V and O atoms along the tunnel axis. Ba_1+xV₈O₂₁ is the first tunnel-type barium vanadium bronze whose structure has been fully determined.     

Demonstration of long-term reliability of a 266-nm, continuous-wave, frequency-quadrupled solid-state laser using beta-BaB(2)O(4)

We report what we believe to be the first operation of more than 1000 h of a 266-nm (cw) frequency-quadrupled solid-state laser with a 100-mW output. We used beta-BaB(2)O(4)(BBO) crystal grown by the Czochralski method to double the green-light (532-nm) wavelength, using an external resonant cavity. The green light was generated with an intracavity frequency-doubled Nd:YVO(4)laser pumped by a 4-W laser diode. When the incident 532-nm power on the external resonant doubler was 500 mW, we generated 100 mW of cw 266-nm radiation with the BBO crystal. The degradation rate seems to be proportional to the strength of the UV optical electric field. We also obtained a relative intensity noise of -130dB/Hz at frequencies of 2 to 10 MHz for 266-nm laser light.     

Acylzirconocene chloride: Formation of carbocycles by palladium-catalyzed cascade reaction

Acylzirconocene chloride complex as an acyl group donor reacts with ω-carbonyl α,β-enones or with bis-enones to give carbocyclic compounds under 10 mol% Pd(OAc)₂-catalyzed conditions, and each reaction was accelerated by the addition of a stoichiometric amount of Me₂Zn. The formation of the carbocycles from ω-carbonyl α,β-enones was considered to be a result of a series of reactions; (i) the formation of Pd(II)-intermediate by an electron transfer from the Pd(0)-catalyst to an α,β-enone function in an initial step, (ii) an acyl group transfer from the acylzirconocene complex to the Pd(II)-intermediate (transmetalation), (iii) the reductive elimination of Pd(0)-metal, and (iv) an intramolecular addition of metal enolate to ω-carbonyl group. On the other hand, the reaction of bis-enones with acylzirconocene chloride under the identical condition afforded reductive cyclization product, bicyclo[3.3.0] octane derivatives, in which acyl group from acylzirconocene complex was not incorporated.     

Film analysis employing subtarget effect using 355 nm Nd-YAG laser-induced plasma at low pressure

The applicability of spectrochemical analysis for liquid and powder samples of minute amount in the form of thin film was investigated using ultraviolet Nd-YAG laser (355 nm) and low-pressure ambient air. A variety of organic samples such as commercial black ink usually used for stamp pad, ginseng extract, human blood, liquid milk and ginseng powder was prepared as film deposited on the surface of an appropriate hard substrate such as copper plate or glass slide. It was demonstrated that in all cases studied, good quality spectra were obtained with very low background and free from undesirable contamination by the substrate elements, featuring ppm or even sub-ppm sensitivity and worthy of application for quantitative analysis of organic samples. The proper preparation of the films was found to be crucial in achieving the high quality spectra. It was further shown that much inferior results were obtained when the atmospheric-pressure (101 kPa) operating condition of laser-induced breakdown spectroscopy or the fundamental wavelength of the Nd-YAG laser was employed due to the excessive or improper laser ablation process.     

Preparation, structure characterization, and oxidation activity of ruthenium complexes with tripodal ligands bearing noncovalent interaction sites

Ruthenium(II/III) complexes with tripodal tris(pyridylmethyl)amine ligands bearing one, two, or three pivalamide groups (MPPA, BPPA, TPPA: amide-series ligands) or neopentylamine ones (MNPA, BNPA, TNPA: amine-series ligands) at the 6-position of the pyridine ring have been synthesized and structurally characterized. The X-ray structure analyses of the single crystals of these complexes reveal that they complete an octahedral geometry with the tripodal ligand and some monodentate ligands. The amide-series ligands prefer to form a Ru(II) complex, while the amine-series ones give a Ru(III) complex. In the presence of PhIO oxidant, the catalytic activities for epoxidation of olefins, hydroxylation of alkane, and dehydrogenation of alcohol have been investigated using the six ruthenium complexes [Ru(II)(tppa)Cl(2)] (1), [Ru(III)(tnpa)Cl(2)]PF(6) (2), [Ru(II)(bppa)Cl]PF(6) (3), [Ru(III)(bnpa)Cl(2)]PF(6) (4), [Ru(II)(mppa)Cl]PF(6) (5), and [Ru(III)(mnpa)Cl(2)]PF(6) (6). Among them, the amide-series complexes, 1, 3, and 5, showed a higher epoxidation activity in comparison with the amine-series ones, 2, 4, and 6. On the other hand, the latter showed a higher reactivity for hydroxylation, allylic oxidation, and C=C bond cleavage reactions compared with the former. Such a complementary reactivity is interpreted by the character of the ruthenium-oxo species involving electronically equivalent formulas, Ru(V)=O and Ru(IV)-O.     

Synthesis of 1-azabicyclo[3.3.0]octane derivatives and their effects as piracetam-like nootropics

A useful pharmaceutical intermediate, 5-nitromethyl-1-azabicyclo[3.3.0]octane (1), was prepared in one step from 1,7-dichloro-4-heptanone (4) under mild conditions. Catalytic hydrogenation of 1 over Raney Ni in the presence of sodium hydroxide afforded 5-aminomethyl-1-azabicyclo[3.3.0]octane (2) in high yield. Piracetam analogues 20-23, which were pyrrolidine derivatives involving a 1-azabicyclo[3.3.0]octane ring, were synthesized. Pharmacological tests showed that N-[(1-azabicyclo[3.3.0]octan-5-yl)methyl]-2-oxo-1-pyrrolidineacetamid e (20) improves cerebral function.     

Palladium-catalyzed reaction of acylzirconocene chloride and stereoselective formation of bicyclo[3.3.0] compounds

The acylzirconocene chloride complex as an acyl group donor reacts with omega-unsaturated alpha,beta-enones and -ynones under Pd-Me(2)Zn(Me(2)AlCl)-catalyzed conditions to give stereoselectively bicyclo[3.3.0] compounds through (i) formation of a Pd(II) intermediate by an oxidative addition of the Pd(0) catalyst to an enone function, (ii) cyclization of the Pd intermediate to an omega-unsaturated group, (iii) an acyl group transfer from zirconium to Pd metal, (iv) reductive elimination of the Pd metal, and (v) intramolecular cis-selective aldol reaction. [reaction: see text]     

Application of ion-exchange cartridge clean-up in food analysis I. Simultaneous determination of thiabendazole and imazalil in citrus fruit and banana using high-performance liquid chromatography with ultraviolet detection

A simple, rapid and reproducible analytical method for thiabendazole (TBZ) and imazalil (IMA) in citrus fruit and banana has been developed. The method involves the use of an ion-exchange cartridge for sample clean-up followed by ion-pair high-performance liquid chromatography with ultraviolet detection. The recoveries of TBZ and IMA from citrus fruits spiked at levels of 10 μg/g and 5 μg/g were in the range of 94–98% and 93–98% with coefficients of variation of 0.5–2.2% and 1.6–2.7%, respectively. The recoveries of TBZ and IMA from banana spiked at levels of 3 μg/g and 2 μg/g were 94% and 94% with coefficients of variation 1.1% and 4.9%, respectively. The detection limits for TBZ and IMA were 0.1 μg/g in citrus fruit and 0.05 μg/g in banana.