Solution-phase structural characterization of supramolecular assemblies by molecular diffraction

Structures of four molecular squares based on rhenium coordination chemistry have been characterized in the solution phase using pair distribution function (PDF) analyses of wide-angle X-ray scattering measured to better than 1 A spatial resolution. In this report we have focused, in particular, on a comparison of structures for pyrazine- and bipyridine-edged squares measured in solution with structures determined for these molecules in the solid state using X-ray crystallography and models derived from geometry optimization and molecular dynamics simulations using a classical force field. The wide-angle scattering for these assemblies is dominated by pair correlations involving one or more rhenium atoms, with both edge and diagonal Re-Re interactions appearing prominently in PDF plots. The pyrazine square is characterized by a relatively rigid structure in solution, with PDF peak positions and linewidths corresponding closely to those calculated from crystal structure data. For the bipyridine-edged square, the experimental PDF peaks measured along the molecular sides match the positions and linewidths of the PDF peaks calculated from static models. In contrast, PDF peaks measured across the diagonal distances of the molecular square deviate significantly from those calculated from the static crystallographic and energy minimized models. The experimental data are instead indicative of configurational broadening of the diagonal distances. In this respect, molecular dynamics simulations point to the importance of butterfly type motions that modulate the Re-Re diagonal distance. Indeed, the experimental data are reasonably well fit by assuming a bimodal distribution of butterfly conformers differing by approximately 25 degrees in the Re-Re-Re-Re torsion angle. Additionally, the measurements provide evidence for solvent ordering by the supramolecular assemblies detected as regions of solvent association and exclusion.     

磷钨钼钒杂多蓝光度法测定钼的探索

本文研究了磷钨钼钒四元杂多酸及其还原产物杂多蓝的形成条件、光度性质、组成和在测定高速钢中高钼的应用。试验表明,磷钨钼钒杂多蓝光度法测定钼具有新颖性、高选择性、较高准确性和简便性,适于高速钢中>1％Mo的测定。     

Formation of Molybdenum Blue Nanoparticles in the Organic Reducing Area

Molybdenum blue dispersions were synthesized by reducing an acidic molybdate solution with glucose, hydroquinone and ascorbic acid. The influence of the H/Mo molar ratio on the rate of formation of molybdenum particles was established. For each reducing agent, were determined the rate constant and the order of the particle formation and were established the conditions for the formation of aggregative stable dispersion with the maximum concentration of particles. The dispersed phase is represented by toroidal molybdenum oxide nanoclusters, which was confirmed by the results of UV/Vis, FTIR, XPS spectroscopy and DLS.     

Formation of Molybdenum Blue Particles via the Reduction of a Molybdate Solution with Glucose

Russian Journal of Physical Chemistry A - Molybdenum blue dispersions are synthesized via the reduction of molybdate with glucose in an acidic medium. Spectrophotometry and photon correlation...     

基于磷钼蓝反应测定钴-钼催化剂浸渍液中钼离子含量

基于磷钼蓝反应测定钴-钼催化剂浸渍液中钼离子含量。建立了一个流动注射-磷钼蓝分光光度法测定高浓度钼离子的含量,优化后的条件为:1酸度调节剂为0.5mol·L-1硫酸溶液;2载流为超纯水;3反应试剂为120g·L-1磷酸二氢钾、100g·L-1抗坏血酸及0.3mol·L-1硫酸的混合液;4总流量为2.8 mL·min-1;5酸度调节盘管长度为20cm;6反应盘管长度为250cm。三氧化钼的质量浓度在10.0~300.0g·L-1范围内与峰高呈线性关系,检出限(3s/k)为2.0g·L-1。方法用于钴-钼催化剂钼浸渍液的分析,回收率在99.7%~105%之间,测定值的相对标准偏差(n=11)小于1%。     

Solution-phase synthesis of a muramyl dipeptide analogue MDA

The solution-phase synthesis of a muramyl dipeptide(MDP) analogue of N~α-[4-chlorocinnamoyl-L-alanyl-D-isoglutaminyl]-L-lysine (MDA,2) is reported that possesses the features of easy feasibility,safety and low cost in large scale of synthesis.     

Cooperative assembly of H-bonded rosettes inside a porphyrin nanoring

The melamine·barbiturate H-bonded rosette motif is of comparable dimensions and symmetry to the cavity of a butadiyne-linked 6-porphyrin nanoring. Functionalisation of each of the barbiturate components and the pyrimidine components of a H-bonded rosette with a pyridine ligand leads to a self-assembled hexapyridine ligand, which binds cooperatively to the zinc porphyrin nanoring. UV-vis-NIR and ¹H NMR experiments show that the 7-component assembly forms at concentrations at which neither the H-bonding interactions nor the zinc porphyrin–pyridine interactions are formed in the absence of one of the three components. The mean effective molarities of these rosette complexes are around 200 mM in chloroform at 298 K.

Mixing barbiturates and pyrimidines equipped with pyridine ligands to leads to self-assembly of a hexadentate rosette ligand, which is complementary to a hexameric zinc porphyrin macrocycle.     

硅钼蓝分光光度法测定硅肥中有效硅

本文采用硅钼蓝分光光度法测定硅肥中有效硅的含量,通过研究浸取剂、振荡频率以及称样量等条件对有效硅提取量的影响,确定了样品溶解方式。探讨了酸度、显色时间、波长等因素对硅钼蓝吸光度的影响。同时,对优化后的硅钼蓝分光光度法进行精密度和准确度试验,多次重复测定的极差小于0.60%,标准偏差小于0.20%,加标回收率在98.5%~101.3%之间。结果表明优化后的硅钼蓝分光光度法具有良好的重现性和精密度。     

Ligand‐Directed Template Assembly for the Construction of Gigantic Molybdenum Blue Wheels

Template‐mediated synthesis is a powerful approach to build a variety of functional materials and complex supramolecular systems. However, the systematic study of how templates structurally evolve from basic building blocks, and then affect the templated self‐assembly, is critical to understanding and utilizing the underlying mechanism, to work towards designed assembly. Here we describe the templated self‐assembly of a series of gigantic Mo Blue (MB) clusters 1 – 4 using l ‐ornithine as a structure‐directing ligand. We show that by using l ‐ornithine as a structure director, we can form new template?host assemblies. Based on the structural relationship between encapsulated templates of {Mo₈} ( 1 ), {Mo₁₇} ( 2 ) and {Mo₃₆} ( 4 ), a pathway of the structural evolution of templates is proposed. This provides insight into how gigantic Mo Blue cluster rings form and could lead to full control over the designed assembly of gigantic Mo‐blue rings.     

Spectrophotometric Determination of Tetracyclines in Pure Form and in Pharmaceutical Preparations,by a Molybdenum Blue Method

Abstract

A new and sensitive spectrophotometric method has been developed for the determination of tetracyclines either in a pure form or in Pharmaceuticals, by a molybdenum blue method. The procedure is based on the observation that, in sulphuric acid medium, tetracyclines reduce ammonium molybdate to molybdenum blue, the absorbance of which is proportional to the amount of antibiotic present. The variables affecting development of the color have been investigated and the conditions optimized. Beer's law is obeyed for up to 20 μg/ml of tetracycline HCl and oxytetracycline HCl, 28 μg/ml of demeclocycline HCl, 18 μg/ml of chlortetracycline HCl, 32 μg/ml of doxycycline HCl and 40 μ/ml of rolitetracycline. Molar absorptivities (1 mol^?1 cm^?1) and Sandell's sensitivities (μ cm^?2 per 0.001 absorbance unit) are, respectively: tetracycline HCl 4.9×10⁴ and 0.0098, oxytetracycline HCl 5.4×10⁴ and 0.0092, demeclocycline HCl 1.6×10⁴ and 0.0313, chlortetracycline HCl 5.5×10⁴ and 0.0094, doxycycline HCl 3.4×10⁴ and 0.0141, rolitetracycline 2.7×10⁴ and 0.0195.     

硅钼蓝光度法测定碳化硅中二氧化硅的含量

采用氯化钠-盐酸-氢氟酸溶解碳化硅样品,加钼酸铵使硅酸离子形成硅钼杂多酸,然后用1-氨基-2-萘酚-4-磺酸还原剂将其还原成硅钼蓝,在700nm波长处测定其吸光度,从而测得碳化硅中的二氧化硅含量。考察了称样量、水浴温度、水浴加热时间、样品储存容器、显色反应时间等因素对测定结果的影响,优化了测试条件。二氧化硅的质量浓度在0．25-12．5mg／（100mL）的范围内与吸光度呈良好的线性关系,线性相关系数r=0．99986。加标回收率为99．2％～100．9％,测定结果的相对标准偏差为0．76％（n=6）。     

微波消解-磷钼蓝分光光度法测定钨矿石中的磷含量

针对钨矿石中的微量元素磷,采用混合酸快速微波消解结合磷钼蓝分光光度法进行测定。经选择优化样品的微波消解和实验测定条件,结果表明:HCl+HNO3+HF的混合酸微波消解后的样品,在硫酸介质中,有钼酸铵存在时,用抗坏血酸将磷还原成磷钼蓝络合物,在825nm处比色测定。方法的加标回收率为98.9%~101.6%,结果准确可靠。硅在熔样过程中挥发除去不会干扰测定,砷会干扰实验,可在酸介质中加入碘化钾,使砷还原至低价而不干扰磷的测定。     

用赤霉素作还原剂钼蓝分光光度法测定钢铁中的硅

用赤霉素作还原剂，对硅钼杂多酸的还原反应进行了系统研究。在０．２ｍｏｌ／ＬＨ２ＳＯ４介质中生成硅钼杂多酸之后，赤霉素能在相当宽的酸度范围内将其还原成十分稳定的硅钼蓝，其最大吸收波长为８１０ｎｍ，表观摩尔吸光系数为３．５１×１０４Ｌ·ｍｏｌ－１·ｃｍ－１。方法的检测限为２．９×１０－６ｇ／Ｌ。硅浓度在０～０．８０ｍｇ／Ｌ范围内符合Ｂｅｅｒ定律。该法已用于钢铁中硅的测定。     

Synthesis and properties of cycloparaphenylene-2,5-pyridylidene: a nitrogen-containing carbon nanoring

The first synthesis of a nitrogen-containing cycloparaphenylene, cyclo[14]paraphenylene[4]2,5-pyridylidene ([14,4]CPPy), has been achieved. A palladium-catalyzed stepwise assembly of 2,2'-bipyridine, benzene, and L-shaped cyclohexane units, followed by NaHSO(4)/o-chloranil-mediated aromatization, successfully provided [14,4]CPPy. While the absorption and fluorescence properties of [14,4]CPPy were somewhat similar to those of cycloparaphenylenes (λ(abs) = 344 nm, ε = 7.3 × 10(4) cm(-1) M(-1), λ(em) = 427 nm, Φ(F) = 0.80), it was found that [14,4]CPPy possesses an interesting halochromic property.     

LaF3薄片的液相合成和表征

Single-crystalline LaF3 flakes was synthesized through a facile solution-phase approach in aqueous ammonia and ethylenediamine. Applying the thermal treatment at 100 ℃ for 20 h, the LaF3 recrystallized, grew epitaxially and precipitated into flakes in aqueous ammonia or ethylenediamine. The formation of flakes could be attributed to the coordination effect of the solvent.     

Solution-phase parallel synthesis of a 1140-member ureidothiophene carboxylic acid library

A 1140-library of thiophene ureidoacids was synthesized by the reaction of a set of 60 primary or secondary amines with a number of 19 thieno[3,2-d]- or thieno[2,3-d][1,3]oxazine-2,4-diones. All compounds were obtained by a simple solution-phase combinatorial strategy on a 200-400-mg scale with over 70% yields and purities over 80%. Sixty library members chosen at random were successfully characterized by standard 1H NMR, HPLC/MS, and IR studies. Analgesic, antalgic, and antiinflammatory potential were investigated. The 1140-member ureidothiophene carboxylic acid library will be used in high-throughput screening assays.     

New application of AAO template: a mold for nanoring and nanocone arrays

Nanoring and nanocone arrays were prepared by conical openings of nanopores in as-prepared AAO film as a mold.