A quantum chemical study of silsesquioxanes: H8Si8O12, Me8Si8O12, H@Me8Si8O12, He@Me8Si8O 12 + , and He@Me8Si8O12

Quantum chemical PBE0 and B3LYP/cc-pVTZ, PBE0, B3LYP, RHF and MP2/6-31G(d,p) methods are employed to calculate the structural parameters of octa(silsesquioxane) H₈Si₈O₁₂ and octa(methylsilsesquioxane) Me₈Si₈O₁₂. These molecules and complexes H@Me₈Si₈O₁₂, He@Me₈Si₈O ₁₂ ⁺ , and He@Me₈Si₈O₁₂ have highly symmetric (O _h ) equilibrium configurations. With the use of the PBE0 method and a cc-pVTZ multicenter basis set common for the complex and its components coincidence is achieved between the calculated polarizability of a free He atom and the experimental value of 0.21 ų and the polarizability depression of 0.17 ų was found for He@Me₈Si₈O₁₂. In order to avoid the false conclusion about molecular symmetry the calculations of the structure of silsesquioxanes must be performed with sufficiently high accuracy (Int = ultrafine and Opt = tight in the use of the GAUSSIAN program).     

新型尼龙214,414,614,814,1014和1214的合成与表征

用熔融缩聚法基于十四碳二酸合成了一系列偶偶尼龙，包括尼龙2 14，4 14， 6 14，8 14，10 14，12 14。用红外光谱、元素分析、核磁共振、差示扫描热分析 、热失重分析、热机械分析、粘度法对合成尼龙的结构与性能进行了表征。同时还 初步研究了尼龙12 14的物理性能，发现其物理性能介于尼龙66和聚乙烯之间。     

Stability of nitrogen-oxygen cages N12O2, N14O2, N14O3, and N16O4

Molecules consisting entirely of nitrogen have been studied extensively for their potential as high energy density materials (HEDM). However, many such molecules are too unstable to serve as practical energy sources. This has prompted many studies of molecules that are mostly nitrogen but which incorporate heteroatoms into the structure to provide additional stability. In the current study, cages of three-coordinate nitrogen are viewed as candidates for stabilization by insertion of oxygen atoms into the nitrogen framework. Cages of N12, N14, and N16 with four-membered rings are studied because four-membered rings have been previously shown to be a destabilizing influence. Insertion of oxygen atoms, which converts N-N bonds to N-O-N bonding groups, relieves ring strain and can potentially result in stable molecules. These molecules are studied by theoretical calculations, using Hartree-Fock and Moller-Plesset (MP3 and MP4) theories, to determine the dissociation energies of the molecules. The primary result of the study is that stable molecules can result from oxygen insertion but that oxygen-oxygen proximity destabilizes the insertion products.     

Ein Beitrag zur Kristallstruktur von CuYW2O8, CuHoW2O8 und CuYbW2O8

A Contribution on the Crystal Structure of CuYW₂O₈, CuHoW₂O₈, and CuYW₂O₈ Single crystals of (I) CuY₂O₈, (II), CuHoW₂O₈, and (III) CuYbW₂O₈ were prepared and investigated by X-ray technique. (I) crystallizes with triclinic symmetry, space group C? P1 (a = 5.939 Å, b = 6.042 Å, c = 5.025 Å; α = 112.30°, β = 111.77°; Z = 1). (II) and (III) belong to monoclinic symmetry, space group C? P2/n (II) (a = 10.045 Å, b = 5.808 Å, c = 5.021 Å; β = 94.38°; z = 2 (III) a = 9.948 Å, b = 5.824 Å, c = 5.008 Å; β = 93.36°; Z = 2). The crystal structures will be discussed with respect to other to copper rare earth tungstates.     

含有两个簇阴离子[As_8V_(14)O_(42)(SO_4)]~(6-)的金属-氧簇合物(H_2en)_6[As_8V_(14)O_(42)(SO_4)]_28H_2O的水热合成与晶体结构

合成了一种新的砷-钒-氧簇合物(H2en)6[As8V14O42(SO4)]28H2O(en为乙二胺),用元素分析、IR和TG-DTA等手段进行了表征,并用X射线衍射法测定了晶体结构。结果表明, 该晶体属单斜晶系,P21/c空间群,晶胞参数a = 20.9235(4),b = 11.9382(2),c = 43.5783(6) 牛琤 = 102.13,V = 10642.1(3) ?,Z = 4,Mr = 4678.01,Dc = 2.920 g/cm3,F(000) = 8944,m = 7.437 mm-1,R = 0.0735,wR = 0.1361。结构测定表明,结构中2个簇阴离子{[As8V14O42(SO4)]6-}与有机铵阳离子[H2en]2+之间靠静电作用相结合,同时与H2O通过氢键构成无限的三维骨架结构。