单斜晶系多晶X射线衍射图的指标化

以对二硝基苯为实例，介绍一种与伊滕法和柯亨法不同的单斜晶系粉晶X射线衍射圈的指标化方法．此法无需通过倒易晶格进行指标化、再通过还原晶胞得到正晶胞的指标化和晶格常数，也不需要衍射峰的不缺少，只需将分组，取d测与d计重叠数量最多的一组中误差最小的d测进行计算处理；可较简便地得到结果．     

X-射线粉晶衍射谱图的计算机模拟

编写了一个FORTRAN程序,用于从单晶结构计算粉晶X射线衍射数据,并进一步用ORIGIN软件绘制出粉晶衍射图谱,选择了13个代表性经典化合物进行计算,结果与粉晶卡片上的实验数据相当一致,本文模拟方法,即可弥补粉晶图谱缺乏的不足,也可用于]校验粉晶衍射实验结果的可靠性。     

配合物[Co（NH3）5Br]Br2煌精密X射线粉末衍射与指标化研究

以多晶射中的从头结构测定对其数据收集与处理的要求为依据，获得「Ｃｏ（ＮＨ３）５Ｂｒ」－Ｂｒ２配合物的精密Ｘ射线粉末衍射谱的方法，总结了指标化实验中的问题与对策，得到标题配合物的正交晶系，晶胞参数：ａ＝１．３７１０（１）ｎｍ，ｂ＝１．０７１５（１）ｎｍ，ｃ＝０．６９４７（１）ｎｍ，Ｖ＿１．０２０６（１）ｎｍ＾３，Ｚ＝４，Ｄｘ＝２．５０ｇ．ｃｍ＾－３，Ｆ３０＝８１（０．００７１，５２），Ｍ２０＝４１。     

巯基乙酸锑配合物的合成与X射线粉末衍射数据指标化

一些锑和铋的配合物可以应用于医药研究[1,2 ] ,已合成了许多锑的有机配体配合物[3～ 7] ,但其中大多数没有生物活性。因此 ,研究锑或铋离子的配合物不仅对主族元素化学、生物无机化学而且对医药都有着非常重要的意义。我们用三氯化锑与巯基乙酸液相反应法合成的二巯基乙酸锑 (Ⅲ)配合物 ,其组成为ＨＳｂ(ＳＣＨ2 ＣＯＯ) 2 ,用Ｘ射线粉末多晶衍射数据指标化来研究配合物晶体结构[8] 。1　实验部分1 1　仪器与试剂ＥＡ - 1 1 0 6型元素分析仪 (意大利卡拉欧巴公司制造 ) ,Ｄ Ｍａｘ -ＹＢ型多晶Ｘ射线粉末衍射仪(日本理学 ,ＣｕＫα射线 ,…     

对氨基苯胂酸电化学合成的研究

研究优化电解还原对硝基苯胂酸(p-A)合成对氨基苯胂酸(p-ASA)的工艺条件.实验表明:硫酸浓度、添加剂量、反应温度、投料量等工艺参数对合成产率有显著影响.初步得出比较适宜的电解合成条件为:硫酸浓度10%(bymass,下同)、添加剂量1%(bymass)NaCl、反应温度80℃、投料量71.4g/L、电流密度10A·dm-2.在上述工艺条件下,电解合成产率可达65.8%.     

羟基乙酸钠X射线粉末衍射数据的精确测定与指标化研究

报道了羟基乙酸钠X射线衍射数据的精确测定及指标化结果.羟基乙酸钠为正交晶系,空间群为P2₁212(18),晶胞参数:a=1.0581(1)nm,b=0.6440(1)nm,c=0.5303(1)nm,V=0.3613(1)nm³,Z=4,D_x=1.802g·cm^-3,D_m=1.786g·cm^-3,M₂₀=38,F₃₀=51(0.0088,68),F₅₉=48(0.0081,153).     

对氨基苯胂酸及其氧化物的色谱研究

 用紫外分光光度计分析了对氨基苯胂酸（PABAA）及其氧化物的光谱特征后,在十八烷基键合相硅胶柱上,以甲醇-缓冲液作流动相,研究了二者的容量因子随流动相离子强度、柱温、甲醇含量变化的规律。用季铵盐作离子对试剂,反相离子对色谱法分离PABAA时,分离机理符合高子对机理,在适当条件下,所试验的化合物都可有所保留。对保留值作出贡献的有固定相排阻作用、分配作用以及居次要地位的PABAA与固定相表面剩余硅醇基的相互作用。排阻作用及分配作用的相对重要性与流动相中甲醇和离子对试剂的浓度有关。     

对氨基苯胂酸及其氧化物的色谱研究

用紫外分光光度计分析了对氨基苯胂酸（PABAA）及其氧化物的光谱特征后,在十八烷基键合相硅胶柱上,以甲醇-缓冲液作流动相,研究了二者的容量因子随流动相离子强度、柱温、甲醇含量变化的规律。用季铵盐作离子对试剂,反相离子对色谱法分离PABAA时,分离机理符合高子对机理,在适当条件下,所试验的化合物都可有所保留。对保留值作出贡献的有固定相排阻作用、分配作用以及居次要地位的PABAA与固定相表面剩余硅醇基的相互作用。排阻作用及分配作用的相对重要性与流动相中甲醇和离子对试剂的浓度有关。     

氨基硫脲Schiff碱的合成和X-射线粉末衍射数据的指标化

Schiff碱及其衍生物广泛地应用于化工生产和科学研究，水杨醛缩氨基硫脲Schiff碱的合成和结构已有报导^[1]，但通过X－射线衍末衍射指标化，确定其晶系和晶胞参数的工作未见报道，同样也没见报道D（＋）－葡萄糖缩氨基硫脲的合成和结构表征，为了提高Schiff碱的水溶性和生物活性，我们合成了D（＋）－葡萄糖缩氨基硫脲和水杨醛缩氨基硫脲，并对其进行了组成分析和结构表征。     

Statistical Inference of Distribution of Crystal Size by X-Ray Powder Diffraction

We describe a method to calculate the distribution of sizes of fine crystals from pure powder-diffraction profile using a method of maximum entropy (MAXENT). We apply a Monte-Carlo technique of simulated annealing to seek a global minimum of the error surface in fitting this diffraction profile. We consider pure diffraction profile (instrument de-convoluted) of a powder specimen without lattice imperfection to a significant extent. Under these circumstances, the distribution of the pure diffraction profile can be attributed to the distribution of crystallite size. We applied this method to three cases of crystal sizes having a highly inhomogeneous distribution with certain noise-tolerance. The results agree well with synthetic data of diffraction.     

粉末衍射技术解析青蒿素晶体结构方法学比对研究

以粉末X射线衍射技术(PXRD)表征有机物晶体结构为目的,选取我国第1个全新药物青蒿素(Artemisinin)验证粉晶解析有机物晶体结构方法的合理性。粉晶解析结果为正交晶系,P212121空间群,a=23.98223±0.01624,b=9.42480±0.00645,c=6.34589±0.00439,α=β=γ=90°,Z=4,V=1434.693;单晶解析结果为正交晶系,P212121空间群,a=23.9564(9),b=9.3224(5),c=6.3205(3),α=β=γ=90°,P212121,Z=4,V=1411.55(17)3;两者所确定分子非氢结构键长、键角、二面角的相关系数分别为0.9921、0.9833和0.9997,晶胞参数基本吻合,分子构型相似。结果表明,粉晶X射线衍射技术可以求得较为准确的青蒿素晶胞参数及晶胞内分子构型。     

单辛基磷酸锆的合成及其X射线粉末图的指标化

制得新化合物单辛基磷酸锆,经HF酸重结晶,得到晶形良好的多晶体粉末。用元素分析、IR图谱、TGA和DTA确定该化合物的化学计量式为Zr(C_8H_(17)OPO_3)_2。采用伊滕(Ito)法对其X射线粉末图进行了指标化,确定该晶体属单斜晶系,单斜简单晶格,晶胞参数为:a=1.699nm,b=1.537nm,c=2.454nm,β=123.56°,Z=8。     

面粉中滑石粉的X射线衍射分析

通过四氯化碳分离或高温灰化,X射线衍射分析测定面粉中掺入的滑石粉。其中灰化处理适宜温度为500~750℃。该方法简便、快速,灵敏度高,样品用量少,准确可靠,可推广为检测面粉质量的一种较理想的手段。     

X-Ray Diffraction Study of Aluminum Monoxycarbide

The structural characteristics of aluminum monoxycarbide Al₂OC are refined and systematized. Based on our X-ray diffraction data, three modifications of Al₂OC: -Al₂OC, '-Al₂OC, and '-Al₂OC have been revealed. Structural models are suggested for them.     

New Approaches for Solving Crystal Structures from Powder Diffraction Data

The determination of crystal structures from single crystal diffraction data can generally be carried out routinely and straightforwardly. However, many crystalline solids can be obtained only as microcrystalline powders and are not suitable for investigation by conventional single crystal diffraction methods. In the past, this problem has limited the ability to elucidate the structural properties of such materials. For the wide range of materials in this category, there is clearly a pressing need to develop and exploit techniques that allow crystal structures to be solved from powder diffraction data. Although traditional techniques for structure solution from powder diffraction data have been applied successfully in several cases, these techniques have certain intrinsic limitations, and for the case of organic molecular crystals the challenges that must be overcome are particularly severe. For these reasons, our recent research has focused on the development and implementation of new methodologies for structure solution from powder diffraction data, leading to new “direct-space” techniques for structure solution in which a hypersurface based on the profile R-factor is searched using Monte Carlo or Genetic Algorithm techniques. This paper presents a brief overview of the problems and challenges associated with structure solution from powder diffraction data. The foundations of the techniques that we have developed are described, and illustrative examples (from the field of organic molecular crystals) are given to highlight the application of these techniques.     

X-Ray Diffraction Study of Piperidine Octamolybdate

Piperidine octamolybdate [C₅H₅NH₂]₄[Mo₈O₂₆]·4H₂O (I) has been synthesized and characterized by X-ray diffraction analysis. Crystals I are monoclinic, space group P2₁/n, a=12.892(3), b=9.283(2), c=19.184(4) , =92.50(3)°, V=2293.7(9) ³, Z=2,_calc = 2.317 g/cm³.     

Improving the Accuracy of Small-Molecule Crystal Structures Solved from Powder X-Ray Diffraction Data by Using External Sources

Structural analysis using powder X-ray diffraction data has overcome many obstacles and nowadays is readily applicable for structural analysis of all types of compounds and materials. Being less straightforward than single crystal diffraction, it requires significant users’ input and consequently, implementation of standardized tools to assess the accuracy of crystal structures. This article discusses potential errors in crystal structure solution and refinement of small-molecule structures obtained from PXRD data. Moreover, it proposes how accuracy of these structures can be improved by using high-quality PXRD data, complementary external analytical techniques, knowledge stored in crystal structure databases, as well as an approach to search the parameter space to avoid local minima in testing different sets of geometry restraints.