A kinetic method for <Emphasis Type="Italic">para</Emphasis>-nitrophenol determination based on its inhibitory effect on the catalatic reaction of catalase

The inhibitory effect of para-nitrophenol on the catalytic reaction of catalase was investigated. Michaelis-Menten kinetic parameters were determined from Lineweaver-Burk plots obtained in the absence or in the presence of the inhibitor. The inhibitor pattern, revealed by the Lineweaver-Burk plots, suggested a fully mixed inhibition mechanism. Spectrophotometric monitoring of the indicator reaction: in conjunction with initial rate measurements was employed for the kinetic determination of the inhibitor. Calibration plots of initial rate vs. para-nitrophenol concentration were linear in the concentration range 0.9·10⁻⁵–2.5·10⁻⁵ mol/L and the detection limit was 3·10⁻⁶ mol/L (417 μg/L) para-nitrophenol. Interferences from other phenolic compounds like orto-cresole, meta-and orto-nitrophenol were observed.     

Nation-Teflon bimembrane-supported palladium catalysts for Suzuki coupling reactions

Nation-Teflon bimembrane was used as an efficient support for the preparation and application of heterogeneous palladium catalysts.The supported palladium catalysts exhibit high activity and stability in the Suzuki cross-coupling of aryl bromides with arylboronic acids to afford the corresponding biaryls in good to excellent yields,and can be readily recovered and reused several times without significant loss of activity.     

Reactions of substituted furo[3,2-<Emphasis Type="Italic">b</Emphasis>]pyrrole-5-carboxhydrazides and their biological activity

The reactions of substituted furo[3,2-b]pyrrole-5-carboxhydrazides 1 with 5-arylfuran-2-carboxaldehydes 2, 4,5-disubstituted furan-2-carboxaldehydes 3 and thiophene-2-carboxaldehyde 4 has been studied. The advantage of microwave irradiation on some of these reactions was reflected in the reduced reaction time and increased yields. Reactions of 1 with 4-substituted 1,3-oxazol-5(4H)-ones 11 led to diacylhydrazines 13 or to imidazole derivatives 14 depending on the temperature. 1,2,4-Triazole-3-thione 17 was synthesized by two-step reaction of 1 with phenylisothiocyanate and subsequent base-catalyzed cyclization of thiosemicarbazide 16. The effects of hydrazones 5–10 on inhibition of photosynthetic electron transport in spinach chloroplasts and chlorophyll content in the antialgal suspensions of Chlorella vulgaris were investigated.     

Synthesis,crystal structure and two-photon property studies on a series of complexes derived from a novel Schiff base ligand

A new Schiff base ligand derived from S-benzyldithiocarbazate and 4-[N-hydroxy ethyl-N-(methyl)amino]benzaldehyde (HL, where H is a dissociable proton) and its Ni^II, Cu^II, Zn^II and Pd^II complexes were prepared and fully characterized. The structures of HL and Ni(L)₂ were determined by X-ray diffraction analysis, which revealed that the geometry of the Ni^II ion is square-planar with two equivalent Ni=N and Ni=S bonds, and that the two neighboring molecules in two layers have weak contact. The electronic spectra and solution fluorescence of the ligand and the complexes were studied, and the quantum yields of single-photon fluorescence for the compounds were determined. The compounds possess two-photon absorption (t.p.a.) character and the t.p.a. coefficient and t.p.a. cross-section were determined by the Z-scan technique. Especially, the Zn(L)₂complex and the HL ligand exhibit intensive two-photon fluorescence (t.p.f.) at 800 nm laser pulses in the femtosecond regime.     

Theoretical study on the structure and property relationship of the cationic conjugated polyelectrolytes

A theoretical study using density functional theory was performed to understand the structure/property relationship of the cationic conjugated polyelectrolytes, poly[9,9-bis-(6′-N,N,N-trimethylammonium) hexyl] fluorene-alt-4,7-(2,1,3-benzothiadiazole)] (PFBT-X, where X = Br). The torsion angle between the fluorene and benzothiadiazole units in the PFBT monomer was found to substantially affect the structural and electronic properties of the cationic PFBT monomer. The changes of geometrical parameter, HOMO and LUMO energy levels, and band gap, as well as the absorption maximum are discussed in terms of the torsion in the PFBT monomer structure. For comparison, its neutral analogue, the monomer of poly(9,9-di-n-octylfluorene-alt-benzothiadiazole) (F8BT) was also studied. The length of conjugation backbone was also examined.     

Electrodeposition of nanocrystalline zinc from acidic sulfate solutions containing thiourea and benzalacetone as additives

Nanocrystalline zinc coatings were produced by pulse electrodeposition in acid sulfate bath containing thiourea and benzalacetone additives and characterized by X-ray diffraction and scanning electron microscopy techniques. The influence of benzalacetone concentration and pulse peak current density on the grain size and crystallographic orientation of zinc deposits was investigated. Zinc electrodeposited from additive-free solutions or with one of the two additives is not composed of nanosized crystals. The mixture additives of thiourea and benzalacetone give rise to the formation of particle-like nanocrystalline zinc with a (10ī1) random orientation. A change in peak current density from 2 to 1 A/cm² only increases the grain size from 60 to 62 nm.     

Energy transfer rates and impact sensitivities of two classes nitramine explosives molecules

Some explosives are stable molecules with large energy barriers to chemical reaction, and in shock or impact initiation, a sizable amount of phonon energy must be converted to the molecular internal higher vibrations by multiphonon up pumping. To investigate the relationship between impact sensitivities and energy transfer rates, the number of doorway modes of explosive molecules is estimated by a simple theory in which the rate is proportional to the number of normal mode vibrations. We evaluated frequencies of normal mode vibrations of 13 explosive molecules which are CHNO nitramine-contained and have not been analyzed previously. The number of doorway modes in the regions of 200–700 cm⁻¹ was evaluated by the direct counting method. For more clear investigation of the relationship we have classified these 13 nitramine explosive molecules, by the number of nitramine group they contained, into two groups. There are eight molecules that contained one nitramine group and five molecules that contained poly-nitramine groups. It is found that the number of doorway modes shows a linearly correlation to the impact sensitivities derived from drop hammer tests. This result is in agreement with that of several previous works. Besides, it is also noted in our study that in those nitramine explosives molecules with similar molecular structure (similar number nitramine group they contained) and similar molecular weight, the correlation between the sensitivity and the number of doorway modes is higher. We found that the vibrational frequency of ω corresponds to nitro group motions of every molecule is contributed to the number of doorway modes in the regions of 200–700 cm⁻¹.     

A facile electrochemical synthesis of caffeic acid derivatives in the presence of acetylacetone or methyl acetoacetate in aqueous medium

The anodic oxidation of caffeic acid in the presence of acetylacetone or methyl acetoacetate in aqueous solution has been studied by cyclic voltammetry and controlled-potential electrolysis techniques. The result showed that caffeic acid was oxidized to the corresponding o-benzoquinone, which underwent further Michael-addition with acetylacetone or methyl acetoacetate to produce caffeic acid derivative 3,4-dihydroxy-6-(1-acetylacetone)-yl cinnamic acid 4a or 3,4-dihydroxy-6-(1-acetyl-methylacetate)-yl cinnamic acid 4b.     

含芳硫基的新三唑类化合物的合成及生物活性研究

许多三唑类化合物具有优良的杀菌和植物生长调节活性 ,如三唑酮、三唑醇、烯效唑、烯唑醇等 ,对常见真菌病害具有很好的防治效果 ,并具有增产、抗倒和生长调节作用 ,已成为重要的杀菌剂类型 [1] .为筛选新型高活性三唑类杀菌剂和探讨其活性与结构间的关系 ,我们利用生物等排体理论以常规三唑类杀菌剂三唑酮为先导物设计合成了 1 6个含芳硫基的新三唑类化合物 ,其合成路线如下 :RCCH2 BrO+HNNNB NRCCH2O NNHAC-Na ACBr2NRCCHOBrNN(1 ) (2 ) (3 )3 +SH 　R′B NRCCHOS　R′NN　 (4 )RCCH2 CH2 NMe2 .HClO+HNNNH2 O…     

Synthesis and magnetic properties of poly(p‐phthaloyl‐disacetylaceton‐ethylenediimine) metal complexes

Macrocyclic Schiff‐base ligand, bisacetylaceton‐ethylenediimine (BAE) and its transition metal complexes M(BAE) (M = Cu²⁺, Ni²⁺) were synthesized. The complexes having characteristics of aromatic systems and well‐defined one‐dimensional structures, reacted with p‐phthaloyl chloride, to obtain polymer complexes. The complexes were characterized by elemental analysis, inductively coupled plasma (ICP), FT‐IR, and thermal analysis and show good thermal stability. ESR spectra analysis discovered that there are free radicals in the chain of polymers, indicating that a weak magnetic spin‐exchange interaction operates between the metal ions and free radicals. It is found that, as the bridging p‐phthaloyl group is able to propagate the magnetic exchange interaction, the polymer complexes show paramagnetic properties by measurement of temperature dependence of the magnetic property, and obey Curie–Weiss law. Copyright © 2001 John Wiley & Sons, Ltd.