Variation in coordinative property of two different N<Subscript>2</Subscript>O<Subscript>2</Subscript> donor Schiff base ligands with nickel(II) and cobalt(III) ions: characterisation and single crystal structure elucidation

A nickel(II) and a cobalt(III) complex of two different potentially tetradentate Schiff bases with different binding modes have been synthesised. The nickel(II) complex [NiL¹] · CH₃OH (1) was formed, on reacting the metal salt with a perfectly symmetrical N₂O₂ tetradentate Schiff base ligand H ₂ L ¹ , which is the 1:2 condensation product of 1,3-diamino propane and 2-hydroxyacetophenone. The cobalt(III) complex [Co(HL²)₃] · (ClO₄)₃ · H₂O (2) was synthesised using an asymmetric N₂O₂ tetradentate Schiff base ligand HL ² on condensing N,N-dimethyl-1,3-diamino propane with o-vanillin in 1:1 mmol ratio. Although both Schiff bases are N₂O₂ functionalised, they showed variation in their coordinative property with nickel(II) and cobalt(III) ions. Both the complexes were characterised by IR spectroscopy and cyclic voltammetry and their single crystal structures clearly indicate that 1 is a mononuclear species whereas 2 is a hydrogen-bonded dimer.     

Reactions of the paramagnetic quaternary Mannich base in an alkaline medium

The catalytic action of aqueous NaOH at 20 °C on 2,2,6,6-tetramethyl-3-(N-methyl-piperidiniomethyl)-4-oxopiperidine 1-oxyl iodide rapidly resulted in the formation (k = 57 L mol⁻¹ s⁻¹) of a paramagnetic ketone with an activated double bond: 2,2,6,6-tetramethyl-3-methylidene-4-oxopiperidine 1-oxyl. The latter underwent slow transformation into a nitroxyl biradical containing an activated double bond and a methylene bridge linking positions 3 and 3′. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 421–423, February, 2008.     

Schiff base macrocycles containing pyrroles and pyrazoles

A double nucleophilic substitution reaction of 3,5-bis(chloromethyl)pyrazole with pyrroles generates a novel pyrrole-pyrazole hybrid building block, the pyrazole analogue to tripyrrane. Vilsmeier-Haack formylation produces the corresponding dialdehyde, which was used in the formation of a series of nonaromatic Schiff base macrocycles. NMR and UV/Vis spectroscopy and single-crystal diffractometry were used to characterize the novel macrocycles. The solid-state structures of select free bases and protonated members of this class of macrocycles display a range of intra- and intermolecular hydrogen-bonding patterns that suggest their use in molecular-recognition systems. They also contain an acid-sensitive chromophore. Their acid-base and anion-recognition properties were ascertained; alas, only modest anion-selective spectroscopic signatures could be detected by using UV/Vis and (1)H NMR spectroscopy. The macrocycles proved resistant toward oxidation to their aromatic congeners. The pyrrole-pyrazole building blocks presented are potentially useful for the synthesis of a range of pyrazole analogues of all-pyrrole macrocycles.     

Radioactive contaminants in the subsurface: the influence of complexing ligands on trace metal speciation

Equilibrium thermodynamics is one of the pillars which support safety analyses of repositories for radioactive waste. The research summarized in this review deals with approaches to resolve the problems related to thermodynamic equilibrium constants and solubility of solid phases in the field of radioactive waste management. The results have been obtained at the Paul Scherrer Institut between 1995 and 2005 and comprise the scientific basis of the author’s habilitation thesis in the field of nuclear environmental chemistry. The topics are grouped according to three different levels of problem solving strategies: (1) Critical and comprehensive reviews of the available literature, which are necessary in order to establish a reliable chemical thermodynamic database that fulfils the requirements for rigorous modeling of the behavior of the actinides and fission products in the environment. (2) In many case studies involving inorganic and simple organic ligands a serious lack of reliable thermodynamic data is encountered. There, a new modeling approach to estimate the effects of these missing data was applied. This so called “backdoor approach” begins with the question, “What total concentration of a ligand is necessary to significantly influence the speciation, and hence the solubility, of a given trace metal?” (3) In the field of natural organics, mainly humic and fulvic acids, we face an ill-defined problem concerning the molecular structure of the ligands. There, a pragmatic approach for performance assessment purposes was applied, the “conservative roof” approach, which does not aim to accurately model all experimental data, but allows estimates of maximum effects on metal complexation by humic substances to be calculated.     

Large-scale differential display analysis of T helper cell differentiation

We have developed a novel large-scale multicapillary fluorescent differential display (FDD) platform amenable to further automation. The power of the method is demonstrated by the analysis of T helper cell differentiation. Eight RNA samples from wild type, Stat4 knockout and Stat6 knockout mice were analyzed with 16 anchoring primers and 24 arbitrary primers, resulting in 285 294 sample peaks. Visually selected patterns of differential expression suggest two major regulatory mechanisms: activation and Stat4 genotype. A subset of the findings is reproduced in the confirmatory differential display (DD) that included technical and biological replicates. In a small fragment identification pilot study, we identify Ifi27 and Cct8 to be up-regulated by T cell activation. We present a method for the analysis of electropherogram similarity across large datasets, based on correlation of low-resolution representations of electrophoretic data. We show how it can be applied to analyze experimental and technical variables. Using this method, we demonstrate the effect of activation and genotype. In addition, agreement of our real experimental data to the theoretical basis of DD, as well as issues in anchoring primer selectivity, are studied.     

Nafion Schiff碱化学修饰电极的研究

研制了Nafion-N,N′-双(3-羧基邻羟亚苄基)三亚甲基二胺(Schiff碱)化学修饰电极;研究了电极的伏安特性,探讨了电极反应机理;用红外光谱证实了Hg(Ⅱ)与Schiff碱的可配位性,该电极用于微分脉冲阳极溶出伏安法测定未处理的尿样中痕量汞,较玻碳电极具有更高的灵敏度和较好的抗表面活性物质干扰的能力。     

碘和硫增感剂在卤化银颗粒表面的分布

碘在卤化银微晶中的含量和分布对感光度的影响引起乳剂配方设计者的广泛注意和重视.颗粒中的碘引起其内部结构和表面结构的改变,导致微晶颗粒表面化学及物理性质的改变,从而引起增感敏化斑的位置、分布以及随后潜影斑、灰雾斑的形成等一系列的变化并最终影响乳剂的感光性能.如果我们想有效地控制卤化银乳剂的感光度、灰雾、反差等一系列感光性能,必须调整卤化银乳剂颗粒的表面结构.     

Cu、Zn-SOD酶模型化合物催化O-2歧化作用的研究

本文采用ＮＢＴ法,利用７２１分光光度计,在ｐＨ＝７．８的条件下,测定了前文所合成的含Ｎ、Ｏ的Ｓ的Ｓｃｈｉｆｆ碱及其铜（Ⅱ）、锌（Ⅱ）配合物催化Ｏ２＾－歧化的活性,并探讨了平均抑制率与浓度的关系。     

双(5-磺酸钠水杨醛)缩二胺水溶性席夫碱的合成

水杨醛及其衍生物与某些伯胺类化合物缩合形成的席夫碱及其金属螯合物,具有特殊的抗癌、抗炎、杀菌抑霉等活性,引起了各国化学家的广泛兴趣［１,２］．对水溶性席夫碱金属螯合物的研究,国内外报道较少［３,４］,其合成方法主要采用水杨醛衍生物、金属盐、胺类的“一...     

微波等离子体原子发射光谱法(MP-AES)测定地质样品中的常量和微量元素

建立了微波等离子体原子发射光谱法(MP-AES)测定地质样品中的常量和微量元素的方法,四酸(盐酸+硝酸+高氯酸+氢佛酸)消解样品,得出了使用4200 MP-AES仪分析地化认证参考物质中常规金属元素(Ag,Cu,Ni,Pb和Zn)的结果,测定样品结果的相对标准偏差落在±10%范围内,另外,IEC和FLIC模型可成功校正光谱干扰。MP-AES仪无需使用乙炔等危险气体,极大提高了实验室安全性并显著降低了运行成本。MP-AES仪已成功应用于地化样品的分析中,结果准确可靠。