Synthesis of new 1,3-bis（phenylethynyl）disilazanes

Three new 1,3-bis(phenylethynyl)disilazanes were synthesized from the reaction of 1,3-dichlorodisilazanes with (phenylethy- nyl)lithium,and characterized by infrared (IR) spectra,nuclear magnetic resonance (NMR) and mass spectrometry (MS).     

IR-REMPI double resonance spectroscopy: the near-IR spectrum of NO-Ar revisited

We describe a new approach to IR-UV double resonance spectroscopy of NO-containing van der Waals complexes. The basic idea combines REMPI detection through a hot band transition with a simultaneous frequency scan of the IR and UV lasers in such a way that the combined photon energy is kept constant throughout the scan, matching a UV resonance transition in the system. As a result, the two-dimensional frequency problem is reduced to a fixed number of one-dimensional frequency scans, each defined by a particular photon energy sum. The method is applied to the near-IR spectrum of NO-Ar using hot band detection via the electronic A state of the complex. In the frequency range from 3718 to 3765 cm(-1), we recorded the previously known vibrational bands with improved frequency resolution. The increased sensitivity of the present experiment allowed us to measure for the first time their overtone, combination, and hot bands. Through the comparison with results of a close-coupling (CC) calculation, we were able to assign most of the rovibrational structures of the spectrum. Except for the first intermolecular stretch level, the band positions and rotational structures of the observed bands are in good agreement with the predictions of the CC calculations.     

Synthesis of the 5'-Se-thymidine phosphoramidite and convenient labeling of DNA oligonucleotide

The synthesis of the 5'-Se-derivatized thymidine and phosphoramidite is reported, and the Se-phosphoramidite was incorporated into DNA. Because of its high nucleophilicity, this 5'-Se-moiety permits convenient postsynthetic modification of oligonucleotides. The proof of principle was successfully demonstrated by incorporating fluorescein into DNA. It was also found that the 5'-dye-labeled Se-DNA can be recognized by DNA polymerase as an efficient primer. This novel strategy opens a new avenue for nucleic acid probe preparation and detection.     

From titanium oxydifluoride (TiOF2) to titania (TiO2): phase transition and non-metal doping with enhanced photocatalytic hydrogen (H2) evolution properties

Single-crystalline TiOF(2) crystals with cubical morphology were prepared via a facile solvothermal method and their transformation to anatase TiO(2) under different calcination conditions such as pure argon, moist argon and pure hydrogen sulfide (H(2)S) was explored by using XRD/Raman/UV-Vis/SEM/TEM/SAED. The non-metal sulfur doping was successfully fulfilled and the doped TiO(2) microcubes showed the best photocatalytic H(2) evolution property.     

Divergent synthetic routes for ring expansion or cyclization from 1,4-allylic diol derivatives via gold(I) catalysis or zinc(II) mediation

A new efficient method was developed to transform cyclic alkanols into one-carbon higher homologated ketones using various esters as the leaving groups through gold-catalyzed allylic cation-promoted pinacol-type rearrangement. This reaction, coupled with oxy-Cope rearrangement, provided a new strategy to synthesize five-carbon homologated ring ketones. In addition, using ZnBr(2), 2,5-dihydrofuran products were obtained in moderate to good yields via an intramolecular cyclization process.     

Continuous-time photon-stimulated desorption spectroscopy studies on soft x-ray-induced reactions of CF3Br adsorbed on Si(111)-7×7

Continuous-time core-level photon-stimulated desorption (PSD) spectroscopy was used to study the soft x-ray-induced reactions of CF(3)Br molecules adsorbed on Si(111)-7×7 near the Si(2p) edge (98-110 eV). The monochromatic synchrotron radiation was employed as a soft x-ray light source in the photon-induced reactions and also as a probe for investigating the produced fluorination states of the bonding surface Si atom in the positive-ion PSD spectroscopy. Several different surface coverages were investigated. The PSD spectra from the low-CF(3)Br-covered surfaces show the production of surface SiF species, while those from the high-CF(3)Br-covered surfaces depict the formation of surface SiF, SiF(2), and SiF(3) species. The photolysis cross section of the submonolayer CF(3)Br-covered surface is determined as ～4.3×10(-18) cm(2). A comparison with the results on CF(3)Cl/Si(111)-7×7 surface is discussed.     

A new route for synthesizing cholesterol analogs with fluorocarbon side chains and their liquid-crystalline aliphatic esters

A new and efficient route has been developed to synthesize 17β-(1-methyl-3-perfluoroalkyl)propyl-3β-androsterol (1) in nine steps from hyodeoxycholic acid via selective addition of 1-perfluoroalkyl iodide to 24-norchola-5,22-dien-3β-ol. From (1), the first series of steroidal liquid crystalline aliphatic esters (smectic A) with fluorocarbon side chains has been prepared.     

Magnetic beads as interfacial nanoprobes

We use paramagnetic beads to probe strongly localized magnetic fields from one-dimensional nanomagnets. Using a polarization microscope in reflection mode, we find that light reflected from beads exhibits intensity fluctuations which may help us understand Brownian motion near interfaces. We estimate the height fluctuations and femtonewton forces acting on the beads.     

Base-catalyzed intramolecular hydroamination of conjugated enynes

A de novo intramolecular hydroamination of conjugated enynes was developed using commercially available n-BuLi as a precatalyst. This hydroamination reaction successfully afforded allenyl-substituted pyrrolidines with up to 95% yield. One of the resulting allenyl pyrrolidines was converted to the natural products irniine and irnidine in three steps.