Real-space observation of local anisotropic correlation between buckled dimers on Si(100) induced by a bidentate adsorbed molecule

The anisotropic correlation between buckled dimers on Si(100) was investigated by scanning tunneling microscopy. A bidentate ligand molecule was used to pin two neighboring dimers at 300 K. The chemically pinned dimer induces antiferromagnetic interaction along the dimer rows. Observed results agree well with Monte-Carlo simulations semi-quantitatively.     

Bisphenol A-recognition polymers prepared by covalent molecular imprinting

A specific recognition material for bisphenol A (BPA) was prepared by using a covalent imprinting technique. A chloroform solution containing bisphenol A dimethacrylate as a template, ethylene glycol dimethacrylate as a cross-linking agent and 2,2′-azobis(isobutyronitrile) as an initiator was polymerized by UV initiation. When BPA was removed from the resulting polymer by hydrolysis of the ester bonds with aqueous sodium hydroxide, carboxylic acid residues were generated in the polymer. After the polymer was packed into a stainless steel column, retention factors of BPA and related compounds were measured. The imprinted polymer adsorbed BPA and structurally related compounds such as 4,4′-dihydroxybenzophenone, bis(4-hydroxyphenyl)sulfone and 4,4′-dihydroxybiphenyl. A typical association constant (K_a) was calculated to be 1.72×10⁵ M⁻¹ by Scatchard analysis. Interestingly, 17α- and 17β-estradiol were also bound to the imprinted polymer (K_a=1.68×10⁵ M⁻¹), indicating that the polymer could be used as artificial receptors for screening the compounds having estrogenic action.     

Synthesis of core‐crosslinked carbosilane block copolymer micelles and their thermal transformation to silicon‐based ceramics nanoparticles

Carbosilane fine particles were synthesized by core‐crosslinking of carbosilane block copolymer micelles and they were pyrolytically transformed into silica nanoparticles. The carbosilane block copolymer, poly(1‐(3‐butenyl)‐1‐methylsilacyclobutane)‐block‐polystyrene, (polyBMSB‐b‐polySt), [(m, n) = (31, 16), (54, 30), and (75, 28)], was synthesized by anionic polymerization of BMSB and St, where m and n represent polymerization degrees of BMSB and St segments, respectively. The block copolymer formed micelles in N,N‐dimethylformamide (DMF). The hydrodynamic diameters (D_h) of the micelles evaluated by dynamic light scattering ranged from 40 to 158 nm depending on the copolymer molecular weight. The core of the micelle was cross‐linked by Pt‐catalyzed hydrosilation with 1,2‐bis(dimethylsilylethane). The D_h of the core‐cross‐linked micelles in THF ranged from 56 to 164 nm. These precursor particles were pyrolyzed at 850 °C under N₂ to give ceramic nanoparticles. The diameters of the spherical ceramic particles estimated by AFM ranged from 25 to 60 nm. X‐ray fluorescence analysis of the ceramic products revealed that it consisted of mainly SiO₂ rather than SiC. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3778–3787, 2005     

Solid-phase synthesis of 2,3-diphenylpropionic acid library as VLA-4 antagonists

2,3-Diphenylpropionic acid library for VLA-4 antagonist was synthesized on solid-phase. Comparison of the two synthetic routes via an orthogonal generation of two aromatic amino functional groups are discussed. From this work, several compounds were identified as potent VLA-4 antagonists.     

A stereoselective route towards heliannuol A

Both epimers of Heliannuol A, first heliannane reported in the literature, isolated from Heliannthus annuus, have been prepared individually in a stereoselective route using a ring closing metathesis (RCM) as a key step to obtain the eight-membered ring. Very good overall yield was obtained in both cases.     

Molecular structure and puckering potential of gas-phase 1-pyrroline as determined by microwave and infrared spectroscopy

The microwave spectrum of 1-pyrroline has been measured from 8 to 48 GHz. The transitions have been assigned to those of the ground state and the four lowest excited states of the ring-puckering vibration of monomer, which is a five-membered ring molecule with one CN double bond. The trimer, which exists in the liquid phase, has not been detected in the gas phase. The geometrical structure of the monomer has been estimated by an ab initio calculation and the trimer by a molecular mechanics calculation. The former is consistent with the experimental rotational constants. A gas-phase infrared spectrum has also been measured, and the ring-puckering potential has been determined by an analysis of the combination bands of the ring-puckering mode and the ring-stretching modes. The potential is described using a puckering coordinate, z, as V(z) = az² + bz⁴, where $\text{a = ?3.358(16) × 10}{}^4\text{cm}{}^{\mathrm{?1}}\text{A}\text{?}{}^{\mathrm{?2}}$ and $\text{b = 1.345(9) × 10}{}^6\text{cm}{}^{\mathrm{?1}}\text{A}\text{?}{}^{\mathrm{?4}}$; these values are intermediate of the corresponding values for cyclopentene and 1-pyrazoline. The nuclear quadrupole coupling constants, χ_aa = ?4.39(10), χ_bb = 1.04(10), and χ_cc = 3.35(10) MHz, have been determined by an analysis of well-resolved hyperfine splittings. These constants have been reproduced by an ab initio calculation with a 4-31G(N¹) basis set.     

Analysis of sodium alkylsulphonates using filament heated in-beam electron impact mass spectrometry

Summary By means of the filament heated in-beam method at 280–450° C, the series of sodium alkylsulphonates (RSO₃Na, where R=C₂H₅ to n-C₁₂H₂₅) give very simple mass spectra: Na⁺, [RSO₃Na₂]⁺, which is the base peak except for R=n-C₄H₉, [(RSO₃)₂Na₃]⁺ and, in most cases, [(RSO₃)₃Na₄]⁺. Fragmentations other than these three or four peaks are observed only in the case of n-heptylsulphonate. The proposed method of analysis for simple alkylsulphonic acids is applicable to ordinary electron-impact mass spectrometers.

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Analyse von Natrium-alkylsulfonaten durch Elektronenstoß-Massenspektrometrie mit Probenerhitzung im Elektronenstrahl

Zusammenfassung Mit Hilfe dieser Methode (280–450° C) erhält man für Natriumalkylsulfonate (RSO₃Na mit R=C₂H₅ bis n-C₁₂H₂₅) sehr einfache Massenspektren: Na⁺, [RSO₃Na₂]⁺ (Basispeak mit Ausnahme von R=n-C₄H₉), [(RSO₃)₂Na₃]⁺ und in den meisten Fällen [(RSO₃)₃Na₄]⁺. Andere Fragmentierungen als diese 3 oder 4 Peaks wurden nur bei n-Heptylsulfonat beobachtet. Dieses Verfahren zur Analyse einfacher Alkylsulfonsäuren ist für übliche Elektronenstoß-Massenspektrometer verwendbar.