Effects of low polymer content in a liquid-crystal microlens

A small number of bifunctional monomers are mixed with a nematic liquid crystal (LC) and cured with a distributed electric field, which is produced by a circular-hole-patterned electrode structure. A gradient type of lens, that is, a LC microlens, is investigated for various polymer concentrations. Addition of 3% polymer is enough to freeze the gradient-index properties of the structure in the form of a convex lens, and a polymer-stabilized LC microlens is demonstrated. Although a lower concentration of polymer cannot hold the distribution properties in a curing process, it can maintain the variable focus as a nematic material can. The polymer networks can also eliminate the disclination line that usually appears and causes the lens in this type of LC device to deteriorate.     

Iron-catalysed green synthesis of carboxylic esters by the intermolecular addition of carboxylic acids to alkenes

Iron triflate, in situ-formed from FeCl3 and triflic acid, or FeCl3 and silver triflate efficiently catalyse the intermolecular addition of carboxylic acids to various alkenes to yield carboxylic esters; the reaction is applicable to the synthesis of unstable esters, such as acrylates.     

H-atom abstraction reaction for organic substrates via mononuclear copper(II)-superoxo species as a model for DbetaM and PHM

Hydrogen atom abstraction reactions have been implicated in oxygenation reactions catalyzed by copper monooxygenases such as peptidylglycine alpha-hydroxylating monooxygenase (PHM) and dopamine beta-monooxygenase (DbetaM). We have investigated mononuclear copper(I) and copper(II) complexes with bis[(6-neopentylamino-2-pyridyl)methyl][(2-pyridyl)methyl]amine (BNPA) as functional models for these enzymes. The reaction of [Cu(II)(bnpa)]2+ with H2O2, affords a quasi-stable mononuclear copper(II)-hydroperoxo complex, [Cu(II)(bnpa)(OOH)]+ (4) which is stabilized by hydrophobic interactions and hydrogen bonds in the vicinity of the copper(II) ion. On the other hand, the reaction of [Cu(I)(bnpa)]+ (1) with O2 generates a trans-mu-1,2-peroxo dicopper(II) complex [Cu(II)2(bnpa)2(O2(2-]2+ (2). Interestingly, the same reactions carried out in the presence of exogenous substrates such as TEMPO-H, produce a mononuclear copper(II)-hydroperoxo complex 4. Under these conditions, the H-atom abstraction reaction proceeds via the mononuclear copper(II)-superoxo intermediate [Cu(II)(bnpa)(O2-)]+ (3), as confirmed from indirect observations using a spin trap reagent. Reactions with several substrates having different bond dissociation energies (BDE) indicate that, under our experimental conditions the H-atom abstraction reaction proceeds for substrates with a weak X-H bond (BDE < 72.6 kcal mol(-1)). These investigations indicate that the copper(II)-hydroperoxo complex is a useful tool for elucidation of H-atom abstraction reaction mechanisms for exogenous substrates. The useful functionality of the complex has been achieved via careful control of experimental conditions and the choice of appropriate ligands for the complex.     

Synthesis and properties of DNA complexes containing 2,2,6,6-tetramethyl-1-piperidinoxy (TEMPO) moieties as organic radical battery materials

We report here the first example of organic radical battery with DNA. Though there is a growing interest in DNA/cationic-lipid complexes as promising gene delivery vehicles, few efforts have been focused on the use of such complexes as advanced materials for organic optoelectronic applications. The present article describes how substitution of the sodium counter cation of DNA with cationic amphiphilic lipid(1-4) provided novel DNA-lipid complexes that contain TEMPO radicals, in which the actual mole ratio of phosphate to lipid was 1:0.84 to 1:0.16. All the TEMPO-containing DNA-lipid complexes displayed reversible two-stage charge/discharge processes, the discharge capacities of which were 40.5-60.0 A h kg(-1). In particular, the capacity of a DNA-lipid(3)-based cell reached 60.0 A h kg(-1), which corresponds to 192 % relative to its theoretical value for the single-electron one-stage process, indicating a two-electron process.     

A caffeine-sensitive membrane electrode: previous misleading report and present approach

Although a previous study [S.S.M. Hassan, M.A. Ahmed, M.M. Saoudi, Anal. Chem. 57 (1985) 1126] had shown that a caffeine-sensitive electrode made with picrylsulfonate and 1-octanol as a cation-exchanger and a solvent mediator, respectively, had a wide working pH range (5.5–9.5) and exhibited a Nernstian response, we could not find such response in this electrode. The present result was reasonable, because the pK_a value of caffeinium ion was reported to be around 0.7 and the neutral form of caffeine was predominant in the pH range examined. Thus, we reinvestigated the response characteristics of a caffeine electrode, taking into consideration the pK_a value, and constructed a new electrode with a combination of the lipophilic cation-exchanger, tetrakis[3,5-bis(2-methoxyhexafluoro-2-propyl)phenyl]borate (HFPB), and the solvent mediator with high degree of dielectric constant, 2-fluoro-2′-nitrodiphenyl ether (FNDPE). This electrode showed a pH-dependent response to caffeinium ion and gave a detection limit of 50 μM with a slope of 55 mV per concentration decade at pH 2. The use of other solvent mediators was less effective than that of FNDPE. The electrode was applied for the determination of caffeine in some central stimulants.     

Determination of (R)-xanthoanthrafil, a phosphodiesterase-5 inhibitor, in a dietary supplement promoted for sexual enhancement

We describe here the first case of the finding of xanthoanthrafil, a phosphodiesterase-5 inhibitor, in a dietary supplement. A methanol extract of the supplement product was first analyzed by TLC and HPLC. The results indicated that the extract contained an unknown compound. The molecular weight of the compound was 389 and the accurate mass showed its elemental composition to be C(19)H(23)N(3)O(6). Combined with this data, NMR analysis revealed the planar structure of the unknown compound to be N-(3,4-dimethoxybenzyl)-2-(1-hydroxypropan-2-ylamino)-5-nitrobenzamide. The R-configuration of this compound had been synthesized as a phosphodiesterase-5 inhibitor, formerly reported as FR226807 by Fujisawa Pharmaceutical Co., Ltd. The absolute configuration of the isolated compound was estimated to have R-configuration by its optical rotation. Considering its general properties, this compound is renamed as (R)-xanthoanthrafil with the agreement of Astellas Pharma Inc. which is the successor of Fujisawa Pharmaceutical Co., Ltd. Quantitative analysis revealed that the content of (R)-xanthoanthrafil in the product was about 31 mg/capsule.     

Present status of the 129Xe comagnetometer development for neutron EDM measurement

A ¹²⁹Xe comagnetometer designed for the measurement of neutron electric dipole moment (nEDM) as precisely as 1 × 10^?27e cm is presented. Highly nuclear spin polarized ¹²⁹Xe are introduced into an EDM cell where the ¹²⁹Xe spin precession is detected by means of the two-photon transition. The geometric phase effect (GPE) which generates the false nEDM was quantitatively discussed and the systematic error of nEDM from the GPE was estimated considering the buffer-gas suppression due to Xe atomic collisions. Research and development are in progress to construct the ¹²⁹Xe comagnetometer with a field sensitivity of 0.3 fT. At present, about 70 % nuclear spin polarized ¹²⁹Xe atoms have been obtained in a spin exchange opitial pumping cell, that are in the process of being transferred into the EDM cell via a cold trap.     

Development of mesoporous ZSM-12 zeolite and its application in alkylation of 2-methylnaphthalene

Desilicated MTW zeolite was evaluated in methylation of 2-methylnaphthalene (2-MN) in a fixed-bed flow reactor at 450 °C. Mesoporous MTW was fabricated via a microwave-assisted desilication process using a harsh alkaline solution to improve the pore volume and the surface area. H-ZSM-12 zeolite was treated with 0.3 M of NaOH solution with different treatment times. Due to the harsh alkaline treatment, micropores were blocked by the deposition of the removed atoms. Due to the importance of methylnaphthalenes intermediates, modified MTW zeolites were evaluated in methylation of 2-MN. Methanol (MeOH), 2-MN and 1,3,5-trimethylbenzene (TMB) were fed to the reactor with a molar ratio of 15:15:70. Higher selectivity to 1-methylnaphthalene (1-MN) was observed rather than dimethylnaphthalene and trimethylnaphthalene with a yield of 13.6, 8 and 2.5 mol%, respectively. Moderate conversion up to 24.1 mol% was reached for 30 min reaction.