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91.
A number of novel routes to the alkali metal compounds of hydroquinone M2[p‐C6H4O2] (M = Li, Na, K, Rb, Cs) and M[p‐C6H4O(OH)] (M = K, Rb, Cs) have been synthetically explored. The selective synthesis of the alkali 4‐hydroxyphenolates and 1, 4‐phenylenediolates is based on optimized reaction conditions (solvents, temperatures). All compounds were structurally characterized by means of powder X‐ray diffraction using Rietveld profile refinement including C—C and C—O bond distance restraints. The atomic arrangement of M2[p‐C6H4O2](M = Na, K) (tetragonal, space group: P42/ncm) is characterized by infinite pillars of [M2[3]O2[3]]‐units along the c axis connected by [p‐C6H4O2]2—‐anions with stacking direction along c. The coordinatively unsaturated alkali metals, surrounded by three oxygen atoms, exhibit symmetrical (K) as well as asymmetrical (Na) interactions with the phenylene rings. M[p‐C6H4O(OH] (M = K, Rb) (tetragonal, space group: P4/n) forms hydrogen‐bridged linear chains of [p‐C6H4O(OH)]—‐anions along the c direction. The phenylene planes of neighboring chains have an almost orthogonal arrangement while the interchain planes are parallel. K and Rb are fourfold coordinated by two different oxygen coordination spheres. 相似文献
92.
《Surface and interface analysis : SIA》2003,35(3):246-250
Among the magnetic metal/semiconductor contacts, the Fe/GaAs system has been widely studied owing to its potential applications in electronic devices. In contrast, there are not many studies concerning the Fe/AlxGa1?xAs contact, and in particular there are no reports concerning the changes induced in the interfacial zone by the presence of Al. In this work, thin polycrystalline iron films were deposited by ion beam sputtering at room temperature on a 300 nm thick Al0.25Ga0.75As layer grown by molecular beam epitaxy onto GaAs(001). X‐ray diffraction analysis showed that the iron films are polycrystalline, and indications of a (002) texture of the film were observed. The fine scale analysis of the interface was achieved by high‐resolution transmission electron microscopy (HRTEM) observations, the results of which are compared with the physicochemical information obtained from electron‐induced x‐ray emission spectroscopy, by analysing the Al 3p valence states at the Fe/AlxGa1?xAs interface. The HRTEM experiments on cross‐section samples indicate that the interfacial zone between iron and AlGaAs is limited to <1.5 nm in thickness. X‐ray emission spectroscopy showed the presence of Al atoms in an FeAl‐like environment at the interface, and the existence of wrong bonds and point defects. The estimated width of the perturbed interface (2.0 ± 0.5 nm) is in agreement with the HRTEM results. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
93.
Bis(dimethylamino)trifluoro sulfonium Salts: [CF3S(NMe2)2]+[Me3SiF2]‐, [CF3S(NMe2)2]+ [HF2]‐ and [CF3S(NMe2)2]+[CF3S]‐ From the reaction of CF3SF3 with an excess of Me2NSiMe3 [CF3(NMe2)2]+[Me3SiF2]‐ (CF3‐BAS‐fluoride) ( 5 ), from CF3SF3/CF3SSCF3 and Me2NSiMe3 [CF3S(NMe2)2]+‐ [CF3S]‐ ( 7 ) are isolated. Thermal decomposition of 5 gives [CF3S(NMe2)2]+ [HF2]‐ ( 6 ). Reaction pathways are discussed, the structures of 5 ‐ 7 are reported. 相似文献
94.
Katritzky AR Akhmedov NG Wang M Rostek CJ Steel PJ 《Magnetic resonance in chemistry : MRC》2004,42(7):648-658
The 1H and 13C NMR spectra of compounds 1-11 and 16-22 in CDCl3 and DMSO-d6 solutions allowed structural assignment to regioisomers 1/5 and 2/6 and their regioselective cyclization products 16-18 utilizing one- and two-dimensional NMR techniques (APT, DEPT, NOE difference, COSY, NOESY, HETCOR and gHMQC, gHMBC). Temperature-dependent 1H NMR spectra of 8-anilino-5-(4-methyl-2-pentyl)-2,3-dihydro-1,5-benzothiazepin-4(5H)-one (18) indicated a free energy of activation (deltaG++) of ca 17 kcal mol(-1) for interconversion between rotamers. The 1H and 13C NMR spectra of 20 and 22 containing two chiral centers exhibit duplication of several signals, indicating the existence of two diastereomeric forms. The structure of 4 was unambiguously confirmed by x-ray crystallography. 相似文献
95.
The complex, bis[N‐6‐aminopyridyl‐N‐(1S)‐(+)‐10‐camphorsulfonylamino]palladium, Pd[(S)‐APCS]2, 1 , was prepared by reaction of 2‐[(1S)‐(+)‐10‐camphorsulfonamino]‐6‐aminopyridine with PdCl2 in THF. Complex 1 has been characterized by spectroscopic methods and its structure has been determined by X‐ray crystallography. Crystal data: space group C2, a= 16.082 (2), b = 17.104 (2), c = 13.051 (2)Å, β = 99.95 (1)°, V = 3535.9 (8) Å3, Z = 2 with final residuals R1 = 0.0491 and wR2 = 0.0944. Two independent molecules, (S,S)‐Pd[(S)‐APCS]2, 1a , and (R,R)‐Pd[(S)‐APCS]2, 1b , were found in each asymmetric unit, which exchange to each other via a series of nitrogen inversion and C‐C bond rotation. The inversion energy (ΔGc1≠) and the energy barrier (δGc2≠) were 11.5 ± 0.1 Kcal mol?1 at 246 K and 9.8 ± 0.1 Kcal mol?1 at 199 K, respectively, calculated by dynamic NMR data. 相似文献
96.
Synthesis,structure and catalytic polymerization activity of half‐sandwich cyclometallated iridium complexes
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A series of mononuclear half‐sandwich cyclometallated iridium complexes with Schiff base ligands were synthesized in good yields. Five air‐stable C,N‐chelate mode complexes were obtained smoothly through metal‐mediated C─H bond activation. Treatments of dimeric metal complexes [Cp*IrCl2]2 with ligands L1–L5 afforded the corresponding C,N‐chelate mononuclear half‐sandwich iridium(III) complexes 1 – 5 . These iridium complexes exhibit high catalytic activity for norbornene polymerization. Both steric and electronic effects of the substituted groups have influences on the behaviors of the polymerization process. All complexes were characterized using infrared and NMR spectroscopies and elemental analysis. Molecular structures of complexes 1 , 2 and 5 were further confirmed using single‐crystal X‐ray analysis. 相似文献
97.
98.
99.
Mesoporous molecular sieve SBA‐15 and conventional silica gel were grafted with 3‐[2‐(diethylamino)ethylamino]propyl groups and used as supports for the preparation of deposited palladium catalysts, which were subsequently evaluated in Stille cross‐coupling reaction of aryl bromides. The highest conversions were achieved with the metal‐saturated catalyst resulting from the modified SBA‐15. Influence of various reaction parameters (solvent, additive, temperature, etc.) on the overall yield and selectivity was studied. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
100.
Robert w. Lenz 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(6):945-959
Alkyl α-chloroacrylates and p-substituted α-methylstyrenes were investigated for the effect of polymerization conditions on tacticity, molecular weight, and distribution, and for the relationship between tacticity, glass temperature, and crystalline properties. 相似文献