A New Approach to Bond Valence Parameters for Pb(Ⅱ)-halide Bonds

基于精确的晶体结构数据并设定B=0.037nm以拟合经验参数R0是通常采用的键价参数推导方法.与此相反,作者提出从分子气相电子衍射的键长设定经验参数R0,然后从晶体结构数据拟合经验参数B.以Pb(Ⅱ)—卤素键为例,PbX_2气相电子衍射Pb—X(X=F,Cl,Br,I)键长分别为0.2036,0.2447,0.2598和0.2804nm,经拟合到最佳B值分别为0.0382,0.040,0.040,0.0386nm,与普适参数B值0.037nm有一定的差距.所提出的键价参数不仅得到比较理想的键价值和计算结果,而且保留了键价参数R_0作为单价键长明确的物理意义.The values of bond valence parameters R_0 for the bonds of main group metal halides are usually obtained by systematic analysis of the crystal structure data by assuming B=0.037 nm. In this work, conversely, the values of B were proposed to be fitted with crystal structure data on assuming the values of R_0 equal to the bond lengths of rg accurately determined by gaseous electron diffraction. As an example, the new sets of R_0 /B for the Pb(Ⅱ)-X (X=F, Cl, Br, I) bonds were obtained and fitted as 0.2036/0.0382, 0.2447/0.040, 0.2598/0.040, and 0.2804/0.0386, respectively. Compared with the values of R_0=0.203, 0.253, 0.264, and 0.278 nm based on B=0.037nm for Pb(Ⅱ )-X bonds reported in the literature, these new parameters were not only accurate and reliable for bond valence calculations, but also revealed the physical meaning inherent in every R_0 as unit valence bond length

On the Crystal Structure of Aqua(tetraphenylporphinato)zinc()

标题化合物的分子和晶体结构最初是用照相法进行测定的〔1〕。flEISCHEr等认为，在这个卟啉锌配合物中zn离子处于卟啉大环平面正中央，并上下各络合距离为2.45的水分子，从而形成（4n＋2O）的六配位八面体构型。随后，HOArd等从晶体计算密度和...Abstract The structure of ZnTTP(H2O) is not monoclinic, as reported by Ruan, Zhu, Bu, Zhang, Shao and ChenChinese J.Structure Chemistry, 1998, 17(3):159￣164 but tetragonal.The revised crystal data are a=13.382(5), c=9.672(2) in space group I4/m, Z=2, which are consistent with that reported in the prvious literalures, especially the one published by Golder, Povey, Silver and Jassim Acta Crystallogr., 1990, C46: 1210￣1212

On the crystal structure of aqua(tetraphenylporphinato) zinc(II)

The structure of [ZnTTP(H2O)] is not monoclinic, as reported by Ruan, Zhu, Bu, Zhang, Shao and Chen[Chinese J. Structure Chemistry, 1998, 17(3):159 similar to 164] but tetragonal. The revised crystal data are a=13.382(5), c=9.672(2) Angstrom in space group I4/m Z=2, which are consistent with that reported in the prvious literatures , especially the one published by Golder, Povey, Silver and Jassim [Acta Crystallogr., 1990, C46: 1210 similar to 1212]

A new approach to bond valence parameters for Pb(II)-halide bonds

The values of bond valence parameters R-0 for the bonds of main group metal halides are usually obtained by systematic analysis of the crystal structure data by assuming B=0.037 nm. In this work, conversely, the values of B were proposed to be fitted with crystal structure data on assuming the values of R-0 equal to the bond lengths of r(g) accurately determined by gaseous electron diffraction. As an example, the new sets of R-0/B for the Pb(II)-X (X=F, Cl, Br, I) bonds were obtained and fitted as 0.2036/0.0382, 0.2447/0.040, 0.2598/0.040, and 0.2804/0.0386, respectively. Compared with the values of R-0=0.203, 0.253, 0.264, and 0.278 nm based on B=0.037nm for Pb(II)-X bonds reported in the literature, these new parameters were not only accurate and reliable for bond valence calculations, but also revealed the physical meaning inherent in every R-0 as unit valence bond length

On chiral space groups and chiral molecules

This note explains the relationship (as well as the absence of a relationship) between chiral space groups and chiral molecules (which have absolute configurations). For a chiral molecule, which must crystallize in a chiral space group, the outcome of the absolute configuration determination must be linked to some other properties of the chiral crystal such as its optical activity for the observation to the relevant

Study on the Bond Valence Parameters for Tungsten-oxygen Bonds

根据键价理论中的指数方程sij=exp[(R0 -rij) /B] ,利用晶体结构报告中不同氧化态n的 3 2 9个W—O键长数据 ,选取不同的B值对键价参数R0 进行了拟合 ,建立了一系列R0 —n线性方程 ,并进而得到与W氧化态无关的键价参数R0 =0 1896nm和B =0 0 2 8nm .与文献数据比较 ,本文拟合的键价参数取得了较好的键价和计算结果 ,讨论了几个应用的实例 .Based on the equation s ij=exp[(R 0-r ij)/B] of bond valence approach and 329 W—O bond length data in literature, linear equations of bond valence parameter R 0 with oxidation state n in different B for W—O bonds were established. The new bond valence parameters R 0=0 1896 nm and B=0 028 nm independent of n were also derived. The parameters fitted in this work were proved to be more suitable for the bond valence calculations. Applications of these parameters to some examples were illustrated.国家重点基础研究发展规划 (No.0 0 1CB1 0 890 6)资助项

晶体范德华半径的70年

对过去70年来发表的稀有气体、非金属元素和金属元素的晶体范德华半径重要数值进行了系统分析和总结.从常用的数值中推荐了最可靠值,并指出有关晶体范德华半径值及其应用中的若干问题,以及有待今后进一步研究的方向

Relationship Between SHG EFFect and Crystal Structure in Complexes of Sub-Group Metal Halide and POM

已发现某些金属有机配合物是一类有前景的非线性光学材料，为了系统地探索二次谐波发生（SHg）效应大、综合性能好的新型金属有机配合物非线性光学晶体材料，则有必要探讨它们的性能与结构之间的关系。考虑到某些具有较大二阶极化率的有机分子可能与副族金属卤化物形成配合物，于是对这些配合物的二次谐波效应与晶体结构的关系进行了较系统的研究，发现它们实测的SHg强度的大小与晶体的配位键中离子键和共价键成分的大小相一致。Some organometallic complexes which are a type of potential nonlinear optical materials have been discovered.In order to make a systematic exploration For new organometallic complexes exhibiting large second harmonic generation(SHG)eFFect and good comprehensive properties ,it is necessary to study the relationship between the property and the structure.Considering the possibility of Forming complexes between some organic molecular crystals exhibiting good SHG eFFect and metallic ions of the sub-group,the relationship between the second-harmonic eFFect and the crystal struture of these complexes was investigated systematically.The experimentation discovered that the regularity of their SHG intensity agree with the regularity of the crystal structure.国家自然科学基金、福建省自然科学基