Aggregate manganese Schiff base moieties by terephthalate or acetate: dinuclear manganese and trinuclear mixed metal Mn2/Na complexes

A reaction system consisting of terephthalic acid, NaOH, inorganic Mn(II) or Mn(III) salt, and salicylidene alkylimine resulted in dinuclear manganese complexes (salpn)(2)Mn(2)(mu-phth)(CH(3)OH)(2) (1, salpn = N,N'-1,3-propylene-bis(salicylideneiminato); phth = terephthalate dianion), (salen)(2)Mn(2)(mu-phth)(CH(3)OH)(2) (2, salen = N,N'-ethylene-bis(salicylideneiminato)), (salen)(2)Mn(2)(mu-phth)(CH(3)OH)(H(2)O) (3), and (salen)(2)Mn(2)(mu-phth) (4), while the absence of NaOH in the reaction led to a mononuclear Mn complex (salph)Mn(CH(3)OH)(NO(3)) (5, salph = N,N'-1,2-phenylene-bis(salicylideneiminato)). In addition, a trinuclear mixed metal complex H[Mn(2)Na(salpn)(2)(mu-OAc)(2)(H(2)O)(2)](OAc)(2) (6) was obtained from the reaction system by using maleic acid instead of terephthalic acid. Five-coordinate Mn ions were found in 4 giving rise to an intermolecular interaction and constructing a one-dimensional linear structure. Antiferromagnetic exchange interactions were observed for 1-3, and a total ferromagnetic exchange of 4 was considered to stem from intermolecular magnetic coupling. (1)H NMR signals of phenolate ring and alkylene (or phenylene) backbone of the diamine are similar to those reported in the literature, and the phth protons are at -2.3 to -10.1 ppm. Studies on structure, bond valence sum analysis, and magnetic properties indicate the oxidation states of the Mn ions in 6 to be +3, which are also indicated by ESR spectra in dual mode. Ferromagnetic exchange interaction between the Mn(III) sites was observed with J = 1.74 cm(-1). A quasireversible redox pair at -0.29V/-0.12V has been assigned to the redox of Mn(2)(III)/Mn(III)Mn(II), implying the intactness of the complex backbone in solution.     

BIOCHEMICAL ISOLATION AND SPECTROSCOPIC CHARACTERIZATION OF POSSIBLE PHOTORECEPTOR PIGMENTS FOR PHOTOTAXIS IN A FRESHWATER Peridinium

Photoreceptor pigments have been isolated biochemically from the freshwater dinoflagellate Peridinium gatunense, and characterized spectroscopically. At least four different chromoproteins can be detected in the crude extract and the membrane fraction isolated from the cells absorbing at 580, 638, 667 and 710 nm, which correspond with the maxima in the action spectrum for phototaxis in this organism. Light energy absorbed by shorter wavelength pigments is emitted as fluorescence at wavelengths which are absorbed by pigments with maxima at longer wavelengths. Protein separation on a MonoQ anion exchanger column using fast liquid chromatography resulted in a non-bound fraction and four bound fractions eluted by an NaCI gradient, which differed in their pigment composition.     

A Spectrophotometric Study OE Zirconium Complexes of 4,5-Dihydroxyfluorescein

Zirconium (IV) ions form violet red complex with 4,5-dihydroxyfluorescein in fairly strong mineral acid medium. The reagent has been successfully applied as a metal indicator in the direct EDTA titration of zirconium. The complex formed by 4,5-dihydroxyfluorescein and zirconium ions has been studied spectrophotometrically in 0.1M HCl solution. It is found that when an excess of metal ion is present, a violet red colored complex with metal-ligand ratio of 1:1, (MR) is formed and when an excess of 4,5-dihydroxyfluorescein is present a 1:2 complex (MR₂) may be predominant. The 1:1 complex has maximum absorption at 510 mμ and the 1:2 complex has very low solubility and tends to precipitate out from the solution. Job's method, log-ratio method and gravimetric method were used to establish the composition of complexes. The apparent stability constant of the 1:1 complex is found to be log K_h = 4.46 or K_h = 2.9×10¹ at pH 1.2.     

Linear crystallization and induction-period studies of the growth of calcium sulphate dihydrate crystals

The linear crystallization of well-formed crystallites of calcium sulphate dihydrate from supersaturated solutions has been studied by a microscopic method at temperatures ranging from 25 degrees to 55 degrees . The activation energy is 16 +/- 1.5 kcal/mole for the fast-growing faces. Induction periods in the crystallization of calcium sulphate dihydrate have been determined as a function of solution concentration at temperatures of 25 degrees and 90 degrees .     

卡宾单重态与乙烯环加成反应中的轨道作用图象

卡宾单重态与乙烯环加成反应已有很多计算工作和轨道作用的解释。由于该反应的C_(2v),对称性反应道的反应为禁阻反应,故反应取先由分子平面互相平行而后转向互相垂直的C_s对称性反应道。本文拟就这个反应过程中前线轨道的相互作用及变化情况提出一个简化模型,以期得到对全过程的清晰面象。1.正则轨道图象:     

3,5-diBr-PADAP作锆(Ⅳ)显色剂的分光光度法研究与应用

本文研究了在非离子表面活性剂存在下,用3,5-diBr-PADAP作锆显色剂的胶束增溶分光光度法。在pH1.0～2.0的HCl介质中,配合物吸光度最大且稳定,最大吸收值在610nm处。Zr(Ⅳ)与试剂形成1:2的配合物,摩尔吸光系数为1.10×10~5L·mol~(-1)·cm~(-1),zr(Ⅳ)量在0～30μg/25mL范围内遵守比尔定律。采用钽试剂一苯苹取分离法,适合于钽铌矿中微量锆的测定。     

低压催化氚化亮石松碱的定位效应的研究

近年来,中草药有效成分的研究引起国内外有关学者普遍关注。氚标记中草药有效成分是研究其相应的药代动力学和代谢产物的主要手段,它具有操作简便,条件温和等优点,但是一般氚化方法均不能明确给出氚化位置。而研究氚化定位效应又是药理工作者急待解决的重要课题,所以在很大程度上限制了该项技术的使用范围。最近,郑冬珠等人用FX—100型核磁共振谱仪给出了在PdO催化剂存在条件下,低压氚化亮石松碱的氚化位置及其相对含量。本文在前文基础上,以亮石松碱为底物,根据Fraser和Garnett等人提出的氢—氚同位素交换反应动力学理论,采用CNDO/2法,对PdO催化亮石松碱的立体构型讲行了计算,得出一些有意义的结果。     

Quantum chemical study on the mechanism of the consecutive addition of HCN to aminoacetonitrile

MINDO/3 method has been used to study the mechanism of the consecutive addition ofHCN to aminoacetonitrile.The results obtained for the first three steps show that the reaction isexothermic,and step I is the rate determining step.     

Synthesis of tunable phosphinite-pyridine ligands and their applications in asymmetric hydrogenation

A new class of modular conformationally rigid N,P ligands is conveniently synthesized from readily available starting material. Iridium complexes with these ligands have demonstrated excellent enantioselectivity (up to 99% ee) in the asymmetric hydrogenation of aryl alkenes.     

Determination of dispersity of crushed granite

Summary Experimental crushed granite column breakthrough curves, using ⁹⁹Tc as spike tracer and ³H as invariant tracer, were analyzed by different linear regression techniques. Dispersity of crushed granite and the retardation factor of ⁹⁹TcO₄^- on the crushed granite were determined simultaneously by one linear regression. Dispersity of crushed granite was also obtained with ³H as invariant tracer by the other linear regression. The dispersities found by spike source and invariant source methods are compared. Experimental results show that the dispersity found by the spike source method is close to that found by the invariant source method. This indicates that dispersity is only a characteristic of the dispersion medium.