Metal dilution effects on the spin-crossover properties of the three-dimensional coordination polymer Fe(pyrazine)[Pt(CN)4

The 1A1 left arrow over right arrow 5T2 spin transition has been investigated in the solid solutions of Fe(x)M(1-x)(pyrazine)[Pt(CN)4] (M = Ni or Co, 0 < or = x < or = 1) having a three-dimensional polynuclear structure. Both Ni and Co dilutions tend to decrease the hysteresis width and smooth the transition curves. The enthalpy (entropy) change associated with the spin transition was found to decrease from 26 kJ mol(-1) (84 J K(-1) mol(-1)) for x = 1 to 12 kJ mol(-1) (47 J K(-1) mol(-1)) for 47% Co dilution and to 15 kJ mol(-1) (54 J K(-1) mol(-1)) for 59% Ni dilution. Raman spectroscopy revealed a mixed one- and two-mode behavior in the solid solutions. For the first time, a correlation between vibrational frequencies exhibiting one-mode behavior and the entropy change, which drives the spin crossover, is established.     

Hydrophobic similarity between molecules: a MST-based hydrophobic similarity index

A similarity index based on the hydrophilic/hydrophobic properties of molecules is presented. Such an index is defined based on the fractional partition of the free energy of solvation developed within the framework of the self-consistent reaction field MST model, which divides the free energy of solvation or the free energy of transfer into contributions assigned to the surface elements defining the solute/solvent interface. These surface contributions can be integrated to derive atomic or group contributions. The suitability of the index to compute the molecular similarity based on hydrophobic/hydrophilic properties is examined by considering their application in a variety of test systems, including structure-activity relationships, absorption properties, and molecular recognition. The similarity index is expected to be a very powerful tool in molecular similarity studies for compounds of chemical, biochemical, and pharmaceutical interest.     

Different binding orientations for the same agonist at homologous receptors: a lock and key or a simple wedge?

Using unnatural amino acid mutagenesis, the binding site for serotonin at the novel Caenorhabditis elegans receptor MOD-1 has been probed. As with the closely related serotonin receptor 5-HT3, MOD-1 makes use of a strong cation-pi interaction between the ammonium of serotonin and the indole side chain of a tryptophan. However, the specific Trp used by MOD-1 is different from that used for 5-HT3 (and the nAChR), aligning with a residue more than 40 amino acids distant in sequence space and on a different "loop" of the agonist binding site. This suggests a significant rearrangement of the ligand on binding these two closely related receptors. It is suggested that, unlike enzymes, receptors and other signaling molecules may need only to deliver an agonist to a general binding region, rather than establishing precise drug-receptor interactions.     

高效液相色谱法研究——N,N-二烷基二硫代氨基甲酸合镍(Ⅱ)螯合物配体交换反应的平衡与动力学

In this article, equilibrium and kinetics of the ligand exchange reaction between a series of N,N-disubstituted dithiocarhamate chelates of Nickel (Ⅱ) have been studied by means of high-performance liquid chromatography in various solvents such as chloroform, dichloromethane, methylbenzene, ethyl acetate and DMF (dimethyl formamide) etc. at 30 ℃. The activation parameters of two selected reactions with different disubstituted alkyl groups have been determined in toluene. The experimental results indicate that steric effect of the alkyl groups may influence to some extent the rate of ligand exchange. The reactions of ligand exchange conform to an S_N2 mechanism. Statistical factor seems to enter the evaluation of the equilibrium constants. Solvation effect may contribute to the influence of solvents on reaction rate.     

THE ELECTROCHEMICAL PREPARATION OF POLYPHENOL WITH CONDUCTIBILITY

Polyphenol film deposited on platinum foil can continuously grow with time during the electrolysis of a phenolsolution consisting of 0. 1 mol L~(-1) phenol, 3 mol L~(-1) NaOH and 0.5 mol L~(-1) Na_2SO_4, as has been proved by the methods ofsweep potential, constant potential and constant current, and visible spectra during the electrolysis of phenol. A polyphenolfilm with thickness of 0.11 mm was obtained by the electrolysis of phenol at a constant potential of 0.70 V (versus Ag/AClwith saturated KCl solution). Polyphenol film is inactive and stable in 2 mol L~(-1) H_2SO_4 solution, neutral solution and3 mol L~(-1) NaOH solution and in the potential range between -0.95 and 1.35 V. The usable potential range is dependent onthe pH value. Polyphenol has an ESR signal with a g factor of 2.0049. The conductivity of polyphenol is 1.2×10~(-4) S cm~(-1). Inthe solution of polyphenol dissolved in DMSO, the mobility of polyphenol anions is 8×10~(-9) m~2 s~(-1) V~(-1) at 20℃.     

Anodic electrodeposition of NiTSPP from aqueous basic media

The oxidative electrodeposition of NiTSPP (tetrakis(4-sulfonatophenyl) Ni porphyrin) on ITO electrode from 0.1 M NaOH aqueous solution has been studied, and UV-visible and reflection FTIR spectroscopies have been used to analyze the composition of such film. By use of UV-vis spectroscopy, small absorbance of the film and an almost nulling effect on the Soret band of the porphyrin along the Ni(III)/Ni(II) redox process were observed. The reflection FTIR spectroscopy detected the presence of Ni-OH groups in the reduced film and as well the state of the porphyrin molecules as radical cation. Moreover, the porphyrin has been quantified by means of the area of the vibration bands assigned to the sulfonate groups by using as reference a Langmuir-Blodgett film containing a known surface concentration of NiTSPP. These results lead us propose the formation of a conductor salt by electrocrystallization, with stoichiometries TSPP/Ni(II)(OH)2 and TSPP/Ni(III)OOH, for its reduced and oxidized forms, respectively. In these two forms, the porphyrin rings will be present as radical cation, which may be stabilized through its dimerization or polymerization.     

新显色剂AsA-TB直接光度法测定球墨铸铁中铈组稀土

研究显色剂三溴偶氮胂 (AsA TB)与Ce4 + 的显色反应。在HCl和H2 C2 O4 介质中AsA TB与Ce4 + 生成蓝色的络合物。最大吸收波长位于 644nm ,试剂的最大吸收波长位于 5 2 7nm ,摩尔吸收系数为 1.2× 10 5L·mol-1·cm-1,铈含量在 4～ 30 μg 2 5ml范围内 ,符合比耳定律 ,测定了球墨铸铁中稀土含量 ,结果满意     

聚丙烯加热改性制备大孔吸附树脂的工艺及其应用

This article reported the preparation of macro porous resin by heating polyproplyene and improving its property. The result showed that macro porous resin with good quality and big soil adsorption rote can be prepared when the ration of polypmplyene to soybean salad oil is 1 : 2, the highest heating temperture is 250℃, time of homothermal agitation is 20min and the rote of cooling is 2℃/min.The resin can effectively adsorb waste grease in restaurant wastewater. After removing grease, wastewater is treated with cogulant deposition. CODcr descend to 83mg/l from 790mg/l, which can reach the national discharge standards.     

nbs与取代苯的亲电反应及其应用

选取含不同取代基的甲苯在不同条件下与NBS反应,考察了溶剂极性、取代基的电子效应和温度等因素对反应结果的影响,结果表明,取代反应的区域选择性强烈地依赖于反应溶剂和取代基的电子效应及其数量。随反应溶剂极性的增强,芳环上亲电取代产物的比例增加;随芳环上取代基的推电子能力的增大,亲电取代反应的优势愈加明显;相反,则有利于α-位上的游离基取代。在此基础上,研究了溴化Q0的合成方法,形成了一条新的、简便的溴化Q0的合成路线,收率达86％以上。     

Basic studies of the influence ofβ-cyclodextrin and 2-hydroxypropylβ-cyclodextrin on the photo-oxidation reaction of phenothiazine in inclusion complexes,using fluorescence detection

The photo-oxidation reaction of phenothiazine has been studied in the presence of-cyclodextrin (-CD) and 2-hydroxypropyl-cyclodextrin (HP -CD). The influence of these organized media on the formation of the oxidation photoproduct upon UV irradiation has been investigated. Phenothiazine forms an inclusion complex with the cyclodextrins. The stoichiometry and formation constant of the complex formed with 2-hydroxypropyl -CD have been calculated using the changes of the fluorescence emission signal and of the absorbance of the drug upon inclusion. An increase of the fluorescence intensity of the photogenerated product is attained when it becomes included inside the cyclodextrin cavity.