255. An X-ray study of the phthalocyanines. Part II. Quantitative structure determination of the metal-free compound
255. An X-ray study of the phthalocyanines. Part II. Quantitative structure determination of the metal-free compound
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255. 酞菁的 X 射线研究。
DOI：
10.1039/jr9360001195
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发表时间：
1936
期刊：
影响因子：
--
通讯作者：
J. Robertson
中科院分区：
文献类型：
--
作者：
J. Robertson
已经给出了一些酞菁的晶体结构的初步数据（J.，1935年，第615页）。这些化合物（参见Linstead，J.，1934，1016）形成一系列非常稳定的单斜晶体的同晶系列。本文给出了游离酞菁C_（32）H_（18）N_8的结构的定量测定结果，空间群C%（PZ_a），a= 19.85，B= 4.72，c= 14.8 A.，p= 122.25”，其每体积为1173 A的晶胞具有两个中心对称分子。3; d（实测值）= 1-44;（计算值）= 1 - 45。众所周知，X射线分析法的直接应用在一般情况下受到相位常数不明确的严重限制。可以对X射线晶体反射的强度进行绝对测量，并从这些值计算结构振幅因子（F）的大小。但是F的完整表达式，因为它出现在代表晶格中任何一点的电子密度的傅里叶级数中，是一个以振幅和相位常数为特征的复量。由于X射线晶体反射是在不同的时间和晶体在不同的位置分别记录的，所以在用单晶进行实验时，关于相位常数的相对值的所有信息必然会丢失。然而，通常可以通过试验方法进行分析，利用原子散射能力和它们之间可能的距离的先前知识。傅立叶综合的应用，然后导致初步结果的细化，并通过逐次逼近的方法，最终相当于直接确定原子间的距离。已经进行的分析
PRELIMINARY data on the crystal structure of some of the phthalocyanines have already been given (J., 1935, 615). These compounds (see Linstead, J., 1934, 1016) form an isomorphous series of remarkably stable monoclinic crystals. The present paper gives the results of a quantitative determination of the structure of free phthalocyanine, C32H18N8, space group C%(PZJa), a= 19.85, b= 4.72, c= 14.8 A., p= 122.25", which has two centro-symmetrical molecules per unit cell of volume 1173 A. 3; d (found)= 1-44;(calc.)=It is well known that the direct application of the X-ray method of analysis is severely limited in the general case by the ambiguity of the phase constant. It is possible to make absolute measurements of the intensities of the X-ray crystal reflections, and from these values to calculate the magnitudes of the structure amplitude factors (F). But the complete expression of F, as it occurs in the Fourier series representing the electron density at any point in the crystal lattice, is a complex quantity characterised by an amplitude and a phase constant. As the X-ray crystal reflections are recorded separately, at different times and with the crystal in different positions, all information regarding the relative values of the phase constants is necessarily lost in making the experiment with a single crystal. However, it is usually possible to proceed with the analysis by methods of trial, making use of previous knowledge of the scattering power of atoms and the probable distances between them. The application of the Fourier synthesis then leads to a refinement of the preliminary results, and by a method of successive approximation is equivalent in the end to a direct determination of the interatomic distances. The analyses already carried out