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71.
Abdul Hamid Othman Yang‐Yi Yang Xiao‐Ming Chen Seik Weng Ng 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(8):e318-e319
The three‐coordinate Ag atom in the title compound, [Ag(C7H3N2O6)(C18H15P)2], shows trigonal–planar coordination [P—Ag—P = 147.1 (1)° and ΣAg = 359.0 (3)°]. Adjacent molecules are linked through the O atoms of adjacent nitro groups [Ag?O = 3.205 (3) and 3.302 (4) Å] into a zigzag chain running parallel to the c axis. 相似文献
72.
We have investigated the viscoelastic behaviour exhibited by chiral smectic C* phases in homeotropic orientation. For an appropriate scattering geometry and using the light scattering technique, the orientational diffusivities associated with the Goldsone mode in ferro- and antiferroelectric phases of C11thiobenzoate and C8tolane compounds have been measured. (SmCA*) is about 100 times weaker than (SmC*). This divergence may be largely attributed to the mode of the molecular arrangement in ferro- and antiferroelectric phases, in spite of the same helical structure observed in the two phases. 相似文献
73.
74.
The retention profile of uranyl ions from aqueous thiocyanate media by polyether-type based polyurethane foams (PUFs) has been studied to gain more information regarding the mechanism of extraction. The effect of pH, shaking time, surfactant type, extraction media, temperature and analyte concentration on the retention of uranyl ions onto PUFs has been studied. It has been found that, the sorption of uranyl ions involved in the formation of a ternary complex ion associate of uranyl ion, thiocyanate and PUFs is highly dependent on these parameters. The kinetics and thermodynamics of the uranyl ions sorption have been studied in more detail. The dependency of the extraction on the parameters can be explained via a “solvent extraction,” mechanism. However, owing to the complex nature of the PUFs a dual-mode sorption mechanism involving both absorptions related to “solvent extraction” and an added component for “surface adsorption” may be operated simultaneously. Attempts for quantitative retention and recovery of the uranyl ions in tap and industrial waste water samples by the proposed PUFs columns has been carried out and satisfactory results have been obtained. The cellular structure of the PUF sorbent offer unique advantages over a conventional bulk type sorbents in rapid, versatile effective separation and/or preconcentration of uranyl ions. 相似文献
75.
l-Arabinose was reduced to l-arabinitol and condensed with formaldehyde to give two bis(di-0-methylene-l-arabityloxymethane and two di-O-methylene-l-arabinitol derivatives. Cis-fused 1,3:2,4-Di-O-methylene-l-arabinitol and trans-fused 2,4:3,5-Di-O-methylene-l-arabinitol were also isolated; only the former was affected by the oxidation to give the corresponding aldehyde, which was converted successively to the hydroxy amide, the ethyl hydroxy ester, the corresponding keto ester and vitamin C. 相似文献
76.
77.
Calculation of electric field–temperature (E,T) phase diagram of a ferroelectric liquid crystal near the SmA–SmC_α~* transition 下载免费PDF全文
In this work we perform a theoretical calculation in order to reconstitute the(E–T) phase diagram of a chiral smectic liquid crystal in the vicinity of the SmA–SmC_α~* transition. This reconstruction is carried out on the basis of a thermodynamic calculation of the slope of the curve joining the SmC_α~* domain and the unwound SmC~*. An empiric correction of the mean field term of Landau De-Gennes development is necessary to accomplish this reconstruction. Thereafter, an experimental validation is performed to verify our calculations. 相似文献
78.
Seven tetrazole-thione complexes, [Pd2(κ2-ptt)4]( 1 ), trans-[Pd(k1-S-ptt)2(PPh3)2] ( 2 ), trans-[Pd(k1-S-ptt)2(SPPh3)2] ( 3 ), trans-[Pd(k1-S-ptt)2(OPPh3)2] ( 4 ), [Pd(k1-N-ptt)2(k2-dppe)] ( 5a ), [Pd(k1-S-ptt)2(k2-dppe)] ( 5b ), [Pd(k1-S-ptt)2(k2-dppeS2)] ( 6 ), and [Pd(k1-S-ptt)2(k2-dppeO2)] ( 7 ), were prepared from 1-phenyl-1H-tetrazole-5-thiol (Hptt), with substituted phosphines. These complexes were investigated by CHNS analysis; infrared (IR), nuclear magnetic resonance (NMR) (1H and 31P), and ultraviolet–visible (UV–Vis) spectroscopy; and single-crystal X-ray data for 5b . In Complex 1 , the ptt− ligand adopted μ2- k-N, k-S bridging mode to afford a dimeric complex, whereas in Complexes 2–4 , 6 , and 7 , the ptt− was covalently coordinated via sulfur atom of the thiol group as a solo product. In contrast, in Complex 5 , the ptt− ligand was bonded in a monodentate fashion through a deprotonated tetrazole ring nitrogen atom in isomer 5a or via a thiolato sulfur atom in isomer 5b . These linkage isomers were clearly shown in the 31P-{1H} NMR. To explain the adoption of the ligand binding modes in Complexes 5a and 5b , geometry optimization calculations were carried out on two isomers. Very small differences of all molecular parameters were found between 5a and 5b isomers. This confirms the reason for obtaining two isomers. Also, theoretical studies are made for all compounds, and excellent agreement is obtained with experimental data. The direct band gap (Eg) values are equal to 2.88, 2.85, and 2.45 eV for Complexes 1 , 2 , and 4 , respectively, revealing a semiconductor nature. The inhibition activity of Complexes 1–3 , 5 , and 8 were evaluated versus the growth of four types of bacteria in vitro. The complexes showed a good activity compared with free ligand and a standard antibiotic. 相似文献
79.
Mohamad Riduwan Ramli Muhammad Bisyrul Hafi Othman Azlan ArifinZulkifli Ahmad 《Polymer Degradation and Stability》2011,96(12):2064-2070
A series of highly cross-linked polysiloxane was synthesised via hydrosilylation and condensation reaction. Structural identification using Fourier Transform Infrared (FTIR) and 1H-NMR confirmed their chemical structures. Their thermal and, mechanical properties, and crystallinity, were analysed and related to the level of cross-link density. These systems displayed elevated thermal and hardness properties at an increased cross-link density. Furthermore, the level of crystallinity was reduced as displayed by XRD analysis. Along with this observation, the calculated fractional free volume (FFV) showed a decreasing trend leading to the ‘densification’ effect. It was envisaged that the linear polysiloxane chain segments aligned parallel to each other in a triclinic crystal system to generate a crystalline domain. The spacing between these stacking chains was found to be about 7.2 Å as measured from simulated XRD pattern. 相似文献
80.
P. S. Pereira Silva Raza Murad Ghalib Sayed Hasan Mehdi Rokiah Hashim Othman Sulaiman Ali Jawad 《Journal of chemical crystallography》2010,40(12):1150-1154