Naryl-substituted anthranilamides with intramolecular hydrogen bonds

Hydrogen bonding interaction as one type of non-covalent force has proven itself to be highly efficient for constructing structurally unique artificial secondary structures. Here, the structure of N_aryl-substituted anthranilamide in solution is demonstrated by various NMR technique, the intramolecular hydrogen bonds between amide attached to arylamine of the same ring is proposed, which is supported by its crystal structure in the solid phase. The substituent on the nitrogen atom of arylamine plays an important role in forming the presence of intramolecular hydrogen bonds. The chemical shift of the N_aryl-H downfield changes obviously, due to the formation of intramolecular hydrogen bonds and the deshielding effect of oxygen, and the neighboring C–H is activated and shows downfield protonic signal too. The presence of intramolecular hydrogen bonds probably provides the explanation for the transformation from N_aryl-substituted anthranilamide to imine, which could be converted into 2-aryl quinazolinone finally.     

Phenolic resin as a carbon source for the synthesis of monometallic Mo and bimetallic CoMo carbides via carbothermal reduction route

It was the first time that phenolic resin (PR) was used as a carbon source for the synthesis of nanostructured monometallic Mo and bimetallic CoMo carbides via carbothermal reduction route. The results showed that phase-pure β-Mo₂C can be formed under an Ar atmosphere at 900°C or a H₂ atmosphere above 700°C. However, almost pure CoMo carbides (Co₃Mo₃C and Co₆Mo₆C) can be obtained only under a H₂ atmosphere at a low temperature of 630°C for 24 and 48 h, respectively. The role of PR in the preparation process has been investigated and a detailed formation mechanism was proposed based on the experimental results.     

Bonding of multiple noble-gas atoms to CUO in solid neon: CUO(Ng)n (Ng=Ar, Kr, Xe; n=1, 2, 3, 4) complexes and the singlet-triplet crossover point

Laser-ablated U atoms co-deposited with CO in excess neon produce the novel CUO molecule, which forms distinct Ng complexes (Ng=Ar, Kr, Xe) with the heavier noble gases. The CUO(Ng) complexes are identified through CO isotopic and Ng reagent substitution and comparison to results of DFT frequency calculations. The U[bond]C and U[bond]O stretching frequencies of CUO(Ng) complexes are slightly red-shifted from neon matrix (1)Sigma(+) CUO values, which indicates a (1)A' ground state for the CUO(Ng) complexes. The CUO(Ng)(2) complexes in excess neon are likewise singlet molecules. However, the CUO(Ng)(3) and CUO(Ng)(4) complexes exhibit very different stretching frequencies and isotopic behaviors that are similar to those of CUO(Ar)(n) in a pure argon matrix, which has a (3)A" ground state based on DFT vibrational frequency calculations. This work suggests a coordination sphere model in which CUO in solid neon is initially solvated by four or more Ne atoms. Up to four heavier Ng atoms successively displace the Ne atoms leading ultimately to CUO(Ng)(4) complexes. The major changes in the CUO stretching frequencies from CUO(Ng)(2) to CUO(Ng)(3) provides evidence for the crossover from a singlet ground state to a triplet ground state.     

Efficient Nazarov cyclizations of 2-alkoxy-1,4-pentadien-3-ones

Expeditious and high-yielding Nazarov cyclizations of 2-alkoxy-1,4-pentadien-3-ones are described. An example of a catalytic asymmetric Nazarov cyclization is presented. [reaction: see text]     

Investigation in monolayers of double-chain fluorocarbon amphiphiles Effect of headgroups on molecular packing and interaction between hydrocarbon and fluorocarbon monolayers

The surface pressure-area diagrams of double-chain fluorocarbon amphiphiles with different headgroup compositions show that the amphiphiles arrange almost perpendicularly to the water subphase and the structure of headgroups exerts significant influence on the amphiphile packing. Strong hydrogen bonding and weak electrostatic interaction favor the formation of stable monolayers. Perfluorooctanoic acid (FOA) cannot form monolayer at water/air interface and can only form liquid monolayer in subphase of calcium nitrate solution. Complete phase separation of palmitic acid and a fluorocarbon amphiphile with shorter hydrocarbon spacer group, 1, could be demonstrated in monolayers by using the phase rule of Crisp. The creation of phase-separated monolayers is possible when the monolayer is composed of a mixture of palmitic acid and a fluorocarbon amphiphile with longer hydrocarbon spacer group, 2. It can be suggested that the miscibility of hydrocarbon amphiphiles with fluorocarbon amphiphiles is determined by the hydrocarbon fraction of fluorocarbon amphiphiles.     

金属有机化合物的分析(Ⅶ)——双环戊二烯基钛、锆、铪二卤化物的紫外光谱规律

以1,2-二氯乙烷为溶剂,室温下在200-800nm波长范围内,测定了62个双(取代环戊二烯基)钛、锆、铪二卤化物的吸收光谱。总结提出了这类化合物的吸收规律,归属了各吸收峰并给予了解释。     

二安替比林基-4-羟基苯基甲烷及其与铬(Ⅵ)显色反应的研究

合成了二安替比林基-4-羟基苯基甲烷(DApHM),研究了它与铬(Ⅵ)的显色反应,建立了两个测定铬(Ⅵ)的新体系.在Mn(Ⅱ)和磷酸存在下,DApHM与 Cr(Ⅵ)反应生成橙红色产物,λ_max为435nm.CTMAB和Tween-80对该体系有明显增敏效果,其中CTMAB-DApHM-Cr(Ⅵ)体系ε为1.0 ×10~6;Tween-80-DApHM-Cr(Ⅵ)体系ε为6.9×10~5.Cr(Ⅵ)量在0.1～0.7μg/25mL间符合比尔定律.用于电镀废液和自来水中Cr(Ⅵ)的测定,结果满意.     

Spectrofluorimetric determination of thiols by use of N[P-(2-benzoxazolyl)phenyl]maleimide

The weak fluorescence of N-[P-(2-benzoxazolyl)phenyl]maleimide (BOPM) can be greatly enhanced by thiol-containing compounds. A sensitive and simple spectrofluorimetric method based on the use of BOPM has been developed for the determination of thiols such as cysteine (Cys) and reduced glutathione (GSH). Calibration plots were linear in the concentration range from 0 to 1.6 x 10(-7) mol L(-1) for Cys and 0 to 1.7 x 10(-7) mol L(-1) for GSH. The detection limits (3a) were 2.36 x 10(-10) mol L(-1) for Cys and 1.49 x 10(-10) mol L(-1) for GSH. Many other amino acids (present at 100-fold greater concentrations) did not interfere with the determination. The proposed method has been used for the determination of Cys in protein hydrolysate and cystine electrolyte or GSH in serum, with recoveries of 95.4-103.7%.     

A proximity-dependent surface hybridization strategy for constructing an efficient signal-on electrochemical DNAzyme sensing system

A proximity-dependent surface hybridization strategy is employed for designing a "signal-on" electrochemical DNAzyme biosensor. By taking advantage of the high sensitivity of the PDSH strategy, and by realizing the enzymatic hydrolysis reaction in a homogenous system with a unimolecular design, the proposed biosensor shows a very high sensitivity to target molecules.