Fluorothiocarbonyl compounds. VI. Free-radical polymerization of thiocarbonyl fluoride

Thiocarbonyl fluoride, CF₂?S, and thiocarbonyl chlorofluoride, CFCl?S, undergo addition polymerization in free radical-initiated systems. In addition, both compounds copolymerize with various unsaturated compounds, including typical vinyl and vinylidene monomers. The chlorofluoride, because of its rapid polymerization rate, copolymerizes best with very active monomers, of which 2,3-dichloro-1,3-butadiene is an example. Thiocarbonyl fluoride polymerizes best at low temperatures. The trialkylborane—oxygen redox couple has been adapted to free-radical polymerizations and copolymerizations from ?60 to ?120°C. With such initiation CF₂?S has been copolymerized with terminal and internal olefins, vinyl compounds, allyl compounds, and acrylic esters. Copolymerization with propylene is unusual, in that it proceeds in a manner that strongly favors a product composed of two molecules of CF₂?S for each propylene. In other cases, product compositions are more responsive to the ratio of monomers charged.     

Perfecting imperfect "monolayers": removal of siloxane multilayers by CO2 snow treatment

Self-assembled monolayers (SAMs) of N-(3-triethoxysilylpropyl)-4-hydroxybutyramide were prepared on silicon oxide on silicon (Si/SiO(2)). Initial silane adsorption and high-temperature annealing led to a stable base monolayer with many large over-lying islands of disordered multilayers as a result of the non-self-limited growth process. The disordered multilayers were hydrolyzed and subsequently removed by CO(2) snow treatment. The resulting films were one monolayer thick as measured by ellipsometry. Atomic force microscopy, attenuated total reflection Fourier transform infrared spectroscopy, and contact angle analysis showed that the films were composed of monolayers with full and uniform surface coverage rather than nonuniform coverage by islands or patches of multilayers. Monolayers of octadecyltrichlorosilane were also prepared by multilayer removal via CO(2) treatment, showing the general applicability of the technique toward siloxane SAMs. We believe that CO(2) is an excellent solvent for weakly bound and hydrolyzed molecules that compose multilayers, and this ability to prepare near-perfect monolayer films from imperfect ones allows for less stringent formation conditions.     

O=P(i‐PrNCH2CH2)3NCH3+: Novel effect of quaternization on the structural metrics of the bicyclic cage

The title cation features the longest distance between the bridgehead atoms (3.56 Å) so far recorded for phosphatrane cages despite a nontetrahedral CN_brigeheadC angle (∼114°). The 70.8° N_bridgeheadCCN torsion angles in the bridging moieties produce a substantial twist along the C₃ axis of the structure that does not easily allow racemization of the cage. The resulting rigidity of the twisted cage gives rise to AB patterns for the methylene protons of this cation and its analogues. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10:255–258, 1999     

Electrochemical-hydrothermal Synthesis and Structural Characterization of Zn2(OH)VO4

A new zinc vanadate Zn₂(OH)VO₄ has been synthesized by an electrochemical-hydrothermal method and characterized by single crystal X-ray diffraction. The compound crystallizes in the orthorhombic system, space group Pnma, a = 14.645(1) Å, b = 6.0215(5) Å, c = 8.8757(8) Å, V = 782.7(1) ų, Z = 4, measured at 223 K. In the structure, rutile-type [ZnO₆] octahedral chains are interconnected by [VO₄] tetrahedra to form a framework of composition [Zn(OH)VO₄], the voids of which are filled by Zn cations with trigonal bipyramidal and octahedral coordination. The structure is closely related to that of the adamite-type phases and the minerals descloizite PbZn(OH)VO₄ and tsumcorite Pb_0.5Zn(H₂O)AsO₄.     

Synthesis of Some Novel Methoxyacrylates and Their Biological Activities

Methoxyacrylate fungicides which came from natural product have an excellent,broad spectrum of activities, highly safety and selective to target because of their unique mode of action-inhibit mitochonidrial respiration by blocking electron transfer between cytochrome b and cytochrome c₁, so more attention was paid by many companies in agrochemicals and at least 300 patents was applied until now. For the action of blocking electron transfer,some one suggests this kind of chemicals should not only work on fungi,but also on insects (sure) and weeds. Up to now,no herbicidal activity was reported. So the following compounds Ⅰ (X=O,NR,in patent:X=O,S rarely X=N) were designed and synthesized by introduced some fragment of herbicide.     

Absorption spectra of GaN: film characterization by Urbach spectral tail and the effect of electric field

The absorption tail of undoped and Si-doped GaN films was investigated at different temperatures and under applied electric field. It was found that the spectral dependence of logarithm of absorption coefficient is combined of two linear functions: ln[(hν)]=C₁+(hν−E_g)/U₁ for hν<3.42 eV and ln[(hν)]=C₂+(hν−E_g)/U₂ for 3.44<hν<3.5 eV with Urbach energies U₁=400–470 meV and U₂=10–20 meV. The influence of an electric field effect on the absorption spectra follows the Dow and Redfield theory. It was shown that the intrinsic electric field about 10⁵ V/cm exists in our samples. The implemented analysis of the absorption spectra gives the qualitative method of film characterization.     

Applying sieving to the computation of quadratic class groups

We present a new algorithm for computing the ideal class group of an imaginary quadratic order which is based on the multiple polynomial version of the quadratic sieve factoring algorithm. Although no formal analysis is given, we conjecture that our algorithm has sub-exponential complexity, and computational experience shows that it is significantly faster in practice than existing algorithms.

     

Development of Bicyclo[3.1.0]hexane-Based A3 Receptor Ligands: Closing the Gaps in the Structure–Affinity Relationships

The adenosine A₃ receptor is a promising target for treating and diagnosing inflammation and cancer. In this paper, a series of bicyclo[3.1.0]hexane-based nucleosides was synthesized and evaluated for their P1 receptor affinities in radioligand binding studies. The study focused on modifications at 1-, 2-, and 6-positions of the purine ring and variations of the 5′-position at the bicyclo[3.1.0]hexane moiety, closing existing gaps in the structure–affinity relationships. The most potent derivative 30 displayed moderate A₃AR affinity (Ki of 0.38 μM) and high A₃R selectivity. A subset of compounds varied at 5′-position was further evaluated in functional P2Y₁R assays, displaying no off-target activity.     

Synthesis of chelating trimethylsiloxy diisonitrile ligands and their rhodium(1) complexes. Crystal and molecular structure of [Rh(t-BuDiNC)2]BPh4·1.5CH3CN (DiNC = chelating bidentate isonitrile ligand)

An X-ray crystallographic study, the first of a complex containing a chelating bidentate isonitrile (DiNC) ligand, reveals that [Rh(t-BuDiNC)₂]BPh₄·1.5CH₃CN crystallizes as a “slipped-stacked” face-to-face dimer of two approximately planar [Rh(t-BuDiNC)₂]⁺ cations with a Rh-Rh distance of 3.384 Å, and an angle of 22.7° between the stacking axis and the Rh---Rh vector. The syntheses of two new bidentate isonitrile ligands, SiNC-2 and SiNC-3 are also described. These ligands contain bulky trimethylsiloxy groups ortho to each isonitrile group and differ only in that the SiNC-3 ligand contains an additional CH₂ unit in its backbone. Each reacts with [Rh(COD)Cl]₂ to afford, after metathesis with KPF₆, a complex of the empirical formula [Rh(SiNC-n)₂]PF₆. Spectroscopic results suggest the SiNC-2 complex is dinuclear, with four SiNC-2 ligands bridging the two rhodium atoms. The SiNC-3 complex is mononuclear, but unlike most other mononuclear [Rh(CNR)₄]⁺ complexes, shows no tendency to self-associate in solution. The different structures of these two complexes and the solution behavior of the SiNC-3 complex are attributed to the bulkiness of the trimethylsiloxy groups.