A remarkable effect of ionic liquids in transition-metal-free aerobic oxidation of benzylic alcohols

The transition-metal-free aerobic oxidation of benzylic alcohols is uniquely accelerated by a 1-butyl-3-methylimidazolium hexafluorophosphate (BMI-PF₆)/PhCF₃ biphasic system and Cs₂CO₃ to afford the corresponding ketones in good yields. The reaction system is also applicable to an oxidative cross-esterification of primary benzyl alcohols with a higher aliphatic alcohol.     

Computational studies of room temperature ionic liquid-water mixtures

Room temperature ionic liquids (IL) have been used in numerous applications in chemistry. Addition of water alters many of their properties making it possible to custom design solvents for specific applications. Along with experiments, computational studies using various approaches have provided key insights into the structure and dynamics of IL systems, as well as aggregate formation and phase behavior of the IL/water mixtures. These systems provide computational challenges since ILs and IL/water mixtures are viscous liquids with intrinsically slow processes and structural organization over surprisingly large length scales, which push the limits of applicability of the available techniques. Recent developments in the studies of IL/water mixtures using computational methodologies are reviewed and the future prospects for the field are briefly discussed.     

Water-dispersible ultrathin Au nanowires prepared using a lamellar template of a long-chain amidoamine derivative

Straight ultrathin Au nanowires (NWs) with diameters less than 2 nm were synthesized using the lamellar structure of C18AA in an organogel and its selective adsorption for specific gold surfaces. In addition, the potential to form a bilayer structure with interdigitated hydrocarbon chains enabled the production of water-dispersible Au NWs without morphological change.     

Ultrafast excited state dynamics of fucoxanthin: excitation energy dependent intramolecular charge transfer dynamics

Carotenoids containing a carbonyl group in conjugation with their polyene backbone are naturally-occurring pigments in marine organisms and are essential to the photosynthetic light-harvesting function in aquatic algae. These carotenoids exhibit spectral characteristics attributed to an intramolecular charge transfer (ICT) state that arise in polar solvents due to the presence of the carbonyl group. Here, we report the spectroscopic properties of the carbonyl carotenoid fucoxanthin in polar (methanol) and nonpolar (cyclohexane) solvents studied by steady-state absorption and femtosecond pump-probe measurements. Transient absorption associated with the optically forbidden S(1) (2(1)A) state and/or the ICT state were observed following one-photon excitation to the optically allowed S(2) (1(1)B) state in methanol. The transient absorption measurements carried out in methanol showed that the ratio of the ICT-to-S(1) state formation increased with decreasing excitation energy. We also showed that the ICT character was clearly visible in the steady-state absorption in methanol based on a Franck-Condon analysis. The results suggest that two spectroscopic forms of fucoxanthin, blue and red, exist in the polar environment.     

Laser-induced periodic surface structures formed on the sidewalls of microholes trepanned by a femtosecond laser

Laser-induced periodic surface structures (LIPSSs) were observed on the sidewalls of 300-μm-diameter holes trepanned on cemented tungsten carbide using femtosecond laser pulses at a wavelength of 800 nm. For a circularly polarized beam, LIPSSs were formed at a period of 300 nm and oriented perpendicularly to the plane of incidence on the sidewalls. For a linearly polarized beam, LIPSS formation was dependent on the relative angle α between the polarization direction and the plane of incidence. For relative angles α from 0° to 70° and from 110° to 180°, LIPSS spacing was 300 nm. However, there were two types of LIPSSs coexisting from 70° to 110°. One had a spacing of 120 nm and the other had a spacing that varied from 500 to 760 nm. It was found that the orientation angle of LIPSSs measured between the LIPSS orientation and the plane of incidence had a nonlinear dependence on α. To understand this dependence, a model was proposed in which LIPSSs are assumed to align perpendicularly to the direction of the absorbed electric field lying in the tangent plane of the sidewall of a drilled hole. The calculated results from this model showed good agreement with the experimental results.     

Glucose concentration determination based on silica sol-gel encapsulated glucose oxidase optical biosensor arrays

Optical biosensor arrays for rapidly determining the glucose concentrations in a large number of beverage and blood samples were developed by immobilizing glucose oxidase (GOD) on oxygen sensor layer. Glucose oxidase was first encapsulated in silica based gels through sol-gel approach and then immobilized on 96-well microarrays integrated with oxygen sensing film at the bottom. The oxygen sensing film was made of an organically modified silica film (ORMOSIL) doped with tris(4,7-diphenyl-1,10-phenanthroline) ruthenium dichloride (Ru(dpp)₃Cl₂). The oxidation reaction of glucose by glucose oxidase could be monitored through fluorescence intensity enhancement due to the oxygen consumption in the reaction. The luminescence changing rate evaluated by the dynamic transient method (DTM) was correlated with the glucose concentration with the wide linear range from 0.1 to 5.0 mM (Y = 13.28X − 0.128, R = 0.9968) and low detection limit (0.06 mM). The effects of pH and coexisting ions were systemically studied. The results showed that the optical biosensor arrays worked under a wide range of pH value, and normal interfering species such as Na⁺, K⁺, Cl⁻, PO₄³⁻, and ascorbic acid did not cause apparent interference on the measurement. The activity of glucose oxidase was mostly retained even after 2-month storage, indicating their long-term stability.     

Synthesis,Crystal Structures,and Properties of 6,12‐Diaryl‐Substituted Indeno[1,2‐b]fluorenes

Fused polycyclic indeno[1,2‐b]fluorene derivatives with aryl substituents at the 6,12‐positions have been prepared as a potential antiaromatic 20π electronic system. They showed strong absorptions in the visible region and amphoteric redox properties. The quinoid‐type molecular structures were revealed by X‐ray crystal‐structure analysis, which indicated that the bond lengths of the quinoid unit depend on the aryl substituents. Whereas nucleus‐independent chemical shift NICS(1) calculations indicate the antiaromatic nature of the s‐indacene core, they have higher stability than substituted acene derivatives. The derivatives with difluorophenyl or anthryl groups were stable in solution. Vapor‐deposited thin films showed ambipolar carrier transportation in the field‐effect transistor devices.     

Carbonyl allylations by 3-halopropenes or 2-propenyl mesylate with tin(IV) chloride and tetrabutylammonium iodide

2-Propenyl tin species, prepared from 3-halopropenes or 2-propenyl mesylate with tin(IV) chloride and tetrabutylammonium iodide in dichloromethane, causes nucleophilic addition to aldehydes to produce the corresponding homoallylic alcohols.     

Synthesis and crosslinking reaction of poly(hydroxyurethane) bearing a secondary amine structure in the main chain

This article describes the polyaddition of bifunctional five‐membered cyclic carbonates and diethylenetriamine. The polyaddition proceeded via the selective addition of the primary amino group to the cyclic carbonates to give poly(hydroxyurethane)s bearing a secondary amine structure in the main chain. The resulting poly (hydroxyurethane) having a secondary amine structure was crosslinked by a reaction with a bifunctional dithiocarbonate to give a networked poly(hydroxyurethane–mercaptothiourethane). © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5899–5905, 2005