Polymerization of monoisocyanates by the Pruitt–Baggett adduct

n-Butyl isocyanate (nBIC) was polymerized in bulk by the Pruitt–Baggett adduct (PBA) at ?23, 0.0, and 25.0°C. Polymerization was accompanied by trimerization to the cyclicisocyanurates at all temperatures. Spectroscopic evidences supported the nylon-1 structure for both trimer and polymer. The polymer/trimer ratio and the molecular weight of produced polymers were found to increase with decreasing temperature. The Pruitt–Baggett catalyst (PBC), which is the reaction product of (PBA + H₂O) system, also polymerized nBIC, but with a relatively slower rate. In aromatic and etheric solutions, nBIC was only trimerized by PBA. Copolymerization of nBIC with propylene oxide by PBA and PBC failed. Some selected monoisocyanates were also polymerized by PBA. © 1993 John Wiley & Sons, Inc.     

A Study of the Nitroso Spin Adducts of the Pentacarbonyl Rhenium Radical

Nitrosobenzene (NB) and nitroso-tetr-butane (NtB) were used to trap the photogenerated rhenium pentacarbonyl radical. Self trapped radicals and spin adducts were studied in detail by EPR spectroscopy. In methylene chloride, both nitroxide and anilino spin adducts can be observed with NtB at ?30°. In contrast, only the nitroxide spin adduct of nitrosobenzene was observed in either hexane, or methylene chloride solution. This solvent controlled spin adduct chemistry, can be explained in terms of the solute-solvent interaction.     

Crystallographic report: (2,2′‐Bipyridyl)bis(ethanoldithiocarbamato)zinc(II)

Zn(meadtc)₂(2,2′‐bipy) is a ZnS₃N₂ chromophore with a distorted square pyramidal geometry. The IR band at 1002 cm^?1 and the bond valence sum value of 1.98 confirmed the monodentate dithiocarbamate in coordination. The non‐bonding Zn–S distance is 5.004(3) Å. Copyright © 2004 John Wiley & Sons, Ltd.     

Macrotricyclic host molecules with basket shaped cavities

The syntheses of several macrotricyclic hexalactams (1–3) and of a corresponding hexalactone (4) are described in detail for the first time. The molecules have a basket shaped skeleton and contain a non-collapsible cavity, the size and shape of which is varied by use of spacer groups. Compounds1–3 selectively form crystalline adducts with ethanol as guest; the macrotricyclic hexaester4 does not. Evidence for an interaction of1 with ethanol was obtained by exchange experiments with perdeuteroethanol. Complexation experiments in solution did not show significant host/guest interactions with the guest chosen.     

Stereoselective routes to 3-hydroxy and 3,4-dihydroxy derivatives of 2-aminocyclohexanecarboxylic acid

The Diels-Alder adduct of ethyl (E)-3-nitroacrylate and furan provides a versatile template for the stereoselective synthesis of mono and dihydroxylated derivatives of 2-aminocyclohexanecarboxylic acid (ACHC). The hydroxylated ACHC derivatives can be considered to be useful building blocks for β-peptides.     

碱性水溶液中4Na2SO4·2H2O2·NaCl的分解动力学

以低浓度(30(wt)%)的双氧水制备了硫酸钠-过氧化氢-氯化钠加合物,各组分的含量均接近于理论值,其纯度为99.3%;在323K和333K下,研究了4Na2SO4*2H2O2*NaCl于碱性水溶液中的分解动力学.结果表明,在不同条件下,其分解均为一级反应;随着温度和pH的增加,其分解速率加快.置信水平为95%时k和C0的联合置信域均为椭圆形且面积较小,求得的参数精确度较高;优化出的模型能较准确地描述4Na2SO4*2H2O2*NaCl于碱性水溶液中的分解过程.     

主-客体化学研究进展

以分子识别为基础的主－客体化学作为新兴交叉学科，已成为当今研究的热点。本文概述了主体分子的类型、结构特征、分子识别特性及其在某些领域的应用。参考文献56篇。     

超分子化合物{[8-hydroxyquinolineH]44+·[SiW12O40]4-·2H2O}的水热合成、晶体结构及热稳定性

A supermolecular compound, {[8-hydroxyquinolineH]₄⁴⁺·[SiW₁₂O₄₀]^4-·2H₂O} was synthesized by hydrothermal reaction with silico-tungstic acid and 8-hydroxyquinoline. The crystal of the compound belongs to monoclinic system, space group P2₁/n, with a=1.282 6(6) nm, b=2.292 7(4) nm, c=2.092 0(6) nm, β=95.495(2)°, Z=4, V=6.124 1(7) nm³, D_c=3.791 g·cm^-3, μ=22.568 mm^-1, F(000)=6 200, R₁=0.029 3, wR₂=0.069 3, GOF=1.079. Su-permolecular compound is composed of one SiW₁₂O₄₀^4- with Keggin structure, four protonated cations of 8-hydroxyquinoline, two hydrones. Thermal analysis results showed that the anionic skeleton construction of heteropoly acid in compound decomposed approximately at 349.0 ℃. CCDC: 622142.     

A Photoinduced Reversible Phase Transition in a Dipeptide Supramolecular Assembly

Tunable supramolecular assembly has found various applications in biomedicine, molecular catalysis, optoelectronics, and nanofabrication. Unlike traditional covalent conjugation, non‐covalent introduction of a photoswitchable moiety enables reversible photomodulation of non‐photosensitive dipeptide supramolecular assembly. Under light illumination, a long‐lived photoacid generator releases a proton and mediates the dissociation of dipeptide‐based organogel, thereby resulting in sol formation. Under darkness, the photoswitchable moiety entraps a proton, resulting in gel regeneration. Furthermore, accompanying the isothermal recycled gel–sol transition in a spatially controlled manner, renewable patterns are spontaneously fabricated. This new concept of light‐controlled phase transition of amino acid‐based supramolecular assemblies will open up the possibility of wide applications.     

Crystal and molecular structure ofo-aminobenzoato (o-(p-dimethylaminobenzalidine)benzoato)(o-ammoniobenzoate)dimethyltin(IV), an example of a mixed carboxylate complex of tin

The structure of the title compound, [Me₂Sn(O₂CC₆H₄NH₂-o)(O₂CC₆H₄(N=C(H)C₆H₄NMe₂-p)-o)(^–O₂CC₆H₄NH₃-o)], has been determined at room temperature. The structure features a distorted trigonal bipyramidal coordination geometry for Sn, defined by three O atoms derived from chemically different, monodentate carboxylate ligands and two methyl groups. Crystals are monoclinic, space groupP2₁/n witha=14.718(5),b=10.981(4),c=20.321(3) Å, =110.74(2)°,Z=4; refinement on 2480 reflections gaveR=0.046.