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).     

Infrared and Raman spectra of 8-azaguanine and 8-azaadenine

The IR and Raman spectra of 8-azaguanine and 8-azaadenine have been studied. The spectra of 8AG have been critically examined and compared with those of guanine and 9-methylguanine. Similarly, the spectra of 8-azaadenine have been examined and compared with those of adenine and 9-methyladenine. It has been possible to refute or accept the assignments for certain frequencies proposed earlier in the parent molecules by other workers, and thus almost unambiguous assignments for several frequencies in guanine and adenine as well as in 8AG and 8AA have been obtained. Several frequencies have been explained as combinations involving a 130 cm⁻¹ vibration which has been assigned to the ring-folding mode. It is found that not as many combination bands involving this mode occur in 8AA as those in 8AG. These observations indicate that guanine and 8AG are geometrically more flexible than adenine and 8AA.     

Anharmonic force fields of naphthalene-h8 and naphthalene-d8

The cubic and the quartic semidiagonal anharmonic force fields of naphthalene-h8 and -d8 are obtained using density functional theory (DFT) with the B9-71 functional and a triple-zeta plus double polarization (TZ2P) basis set. The fundamental frequencies computed by second-order vibrational perturbation theory are in very good agreement with the experimental data, with a mean absolute deviation (MAD) of 4 cm(-1) for C(10)H(8) and 6 cm(-1) for C(10)D(8). Some of the fundamental frequencies have been reassigned on the basis of the present results. Only CH stretchings seem to be significantly affected by Fermi resonances, with two shifts larger than 10 cm(-1). Calculated infrared harmonic intensities reproduce the experimental data within 15%, with the exception of CH stretchings affected by a larger error. Scale factors from C(10)H(8) have been tested by deriving the fundamental frequencies of C(10)D(8) from the theoretical harmonic ones. These fundamentals are in nice agreement with those obtained from the C(10)D(8) anharmonic force field. These results support the use of scale factors to calculate the vibration spectra of larger polycyclic aromatic hydrocarbons of great astrophysical interest.     

Pd-katalysierter Deuterium-Austausch am Octa(silsesquioxan)H8Si8O12 zu D8Si8O12

Pd-Catalyzed Deuterium Exchange of Octa(silsesquioxane) H₈Si₈O₁₂ to D₈Si₈O₁₂ Deuterium exchange on octa(silsesquioxane) H₈Si₈O₁₂ to D₈Si₁₈O₁₂ catalyzed by palladium on carbon is reported.     

Ce(C_8H_8)_2和Ce(C_8H_8)_2~-的化学键性质

结合改进的重叠模型Xa-SW法和Ziegler过渡态法,通过将中心原子与配体的作用选成离子聚集、中心原子只有s和p轨道参与成键、中心原子只有d轨道参与成键、中心原子只有f轨道参与成键、中心原子的s、p、d和f轨道同时参与成键5种类型,从能量角度分析了Ce(C_8H_8)_2和Ce(C_8H_8)~-_2的化学键性质。     

Quasi-1D cations 1 infinity [Ni8Bi8S]n + of variable charge: infinite columns 1 infinity [Ni8Bi8S]2+ in the novel compound Ni8Bi8SI2

The new compound Ni(8)Bi(8)SI(2) has been synthesized and its crystal structure determined by X-ray crystallography. The structure contains one-dimensional (1D) cations (1)( infinity )[Ni(8)Bi(8)S](2+) separated by iodine anions. The geometry of the columns is similar to that of the recently reported (1)( infinity )[Ni(8)Bi(8)S](+), and the main difference between them is only their formal charge. Electronic structure calculations and physical properties measurements were performed to analyze the influence of the number of valence electrons on the bonding and properties of compounds containing these 1D cations. It was shown that the removal of one electron (i.e., (1)( infinity )[Ni(8)Bi(8)S](+) --> (1)( infinity )[Ni(8)Bi(8)S](2+)) mainly affects the Ni-S bonding within the cation and essentially has no influence on the intermetallic Ni-Bi bonding. It was found that Ni(8)Bi(8)SI(2) containing double-charged columns has conductivity properties more similar to a pure 1D metal than the congener Ni(8)Bi(8)SI containing mono-charged columns.     

Cyclopentyl derivatives of 8-azahypoxanthine and 8-azaadenine. Carbocyclic analogs of 8-azainosine and 8-azaadenosine

Four types of carboeyclic analogs of 8-azahypoxanthine and 8-azaadenine nucleosides have been prepared. This group of analogs is comprised of derivatives having the (±)-as-3-(hydroxy-methyl)cyclopentyl,(±)-trans-3-hydroxy-cis-4-(hydroxymethyl)cyclopentyl), (±)-trans-2-hydroxy-cis-4-(hydroxymethyl)cyclopentyl, and (±)-trans-2, trans-3-dihydroxy-cis-4-(hydroxymethyl)-cyelopentyl groups at position 3 of 3,6-dihydro-7H-v-triazolo[4,5-d]pyrimidm-7-one and of 7-amino-3H-v-triazolo[4,5-d]pyrimidine. Diazotization of (5-amino-6-chloropyrimidin-4-yl-amino)eyclopentane derivatives and acidic hydrolysis, without isolation of the resulting 7-chloro-3H-v-triazolo[4,5-d]pyrimidines yielded the 8-azahypoxanthine derivatives (III). Treatment of unpurified 7-chloro-3H-v-triazolo[4,5-d]pyrimidines with anhydrous ammonia gave the 8-azaadenine derivatives (IV). The cyclopentane analogs of 8-azaadenylic acid and of 8-aza-adenosine 3′,5′ -cyclic monophosphate were prepared from the 8-azaadenosine analog.     

Isomer stability and bond-breaking energies of N8C8H8 cages

Molecules consisting entirely or predominantly of nitrogen have been extensively investigated for their potential as high-energy density materials (HEDM). Such molecules react to produce N2 and large amounts of energy, but many such molecules are too unstable for practical applications. In the present study, cage isomers of N8C8H8 are studied using theoretical calculations to determine the structural features that lead to the most stable cages and determine the energetics of dissociation for the various isomers. The isomers are evaluated for thermodynamic (isomer vs isomer) stability and kinetic (with respect to dissociation) stability. Density functional theory (B3LYP), perturbation theory (MP2), and coupled-cluster theory [CCSD(T)] are employed, in conjunction with the cc-pVDZ basis set of Dunning. Trends in isomer stability and dissociation energies are calculated and discussed.     

放电温度对LiNi3/8Co2/8Mn3/8O2电化学性能的影响

采用X射线衍射（XRD）、X射线光电子能谱（XPS）、恒流充放电、循环伏安及交流阻抗法，研究了放电温度对LiNi3/8Co2/8Mn3/8O2的倍率特性、锂离子扩散及电荷传递的影响.结果表明， 提高放电温度可显著改善LiNi3/8Co2/8Mn3/8O2的放电容量与倍率放电性能.尽管温度升高使电荷传递活性与锂离子扩散速度都增加，但电荷传递活化能比锂离子扩散活化能大一倍多，表明电荷传递步骤是其电化学反应控制步骤.温度对其电荷传递的影响大于对锂离子扩散的影响.温度升高，电荷传递速率加快，电化学嵌入-迁出反应加速，是其放电容量与倍率放电特性显著改善的主要原因.     

Vibrational spectra of C60.C8H8 and C70.C8H8 in the rotor-stator and polymer phases

C(60).C(8)H(8) and C(70).C(8)H(8) are prototypes of rotor-stator cocrystals. We present infrared and Raman spectra of these materials and show how the rotor-stator nature is reflected in their vibrational properties. We measured the vibrational spectra of the polymer phases poly(C(60)C(8)H(8)) and poly(C(70)C(8)H(8)) resulting from a solid-state reaction occurring on heating. On the basis of the spectra, we propose a connection pattern for the fullerene in poly(C(60)C(8)H(8)), where the symmetry of the C(60) molecule is D(2h). On illuminating the C(60).C(8)H(8) cocrystal with green or blue light, a photochemical reaction was observed leading to a product similar to that of the thermal polymerization.     

8-葵炔基苯并内酰胺-V8的改良合成

8-葵炔基苯并内酰胺-V8是我们最近发现的具有亚基选择性的PKC调节剂,动物实验表明有抗癌活性。本文探讨了一个对于这个化合物的新的合成路线。以4为原料,通过碘基化反应,成环反应,Pd/CuI催化的葵炔与芳基碘代物的偶联反应等关键步骤,以22.4%的收率得到了该化合物。     

Site specificity in cycloadditions of diphenylnitrile imine with 8-substituted-8-azaheptafulvenes and tricarbonyl (8-azaheptafulvene) iron complexes

The reaction of diphenylnitrile imine with 8-substituted-8-azaheptafulvenes is both site and regiospecific and resulted in a mixture of two [8+4]-adducts in high yield. The mechanism of the reaction was investigated. The [8+4]-adducts underwent easily a reversible thermal 1,7-sigmatropic shift involving an sp³ nitrogen centre. Diphenylnitrile imine reacted also with tricarbonyl(8-azaheptafutvene)iron complexes lo give adducts to the CN double bond, the degradative oxidation of which with trimethylamine-N-oxide was investigated. The specificity of the cycloadditions is briefly discussed on the basis of a simple perturbation theory approach.     

Total Synthesis of Several 8, 8",-Biflavones

8,8"-Biflavonoidsareantw0rtantclass0fbiflavonoids.Asasystematicresearchofthe8,8"-biflav0noids,wehavepreviouslyreportedthestudyonthereactionof2'-hydroxychaloneswithl2-H2SO4-DMSOsystem.'InthispaPer,thesynthesisof5,5",7,7',-tetTameth0xy-8,8"-biflavonela2,4,4",7,7"-tetramethoxy-8,8"-biflavone1b',4',4",,5,5,',7,7"-hexamethoxy-8,8"-biflav0ne1c4and4,4"-dibenZyl0xy-5,5",7,7"-tetramothoxy-8,8"-biflavoneldisreported.ThesyntheticmethodisshownintheSchemebelow.2-Hydroxyacet0phenonescondensedwithsubsti…     

"Met-Cars"外接氢化合物Ti8C12H4和Ti8C12H8的Ab Initio研究

用量子化学从头算方法，对Ｔｉ８Ｃ１２（Ｔｄ）进行了几何构型优化，结果表明，Ｔｉ３Ｃ１２（Ｔｄ）的化学动力学性质不稳定，化学性质活泼，在此基础上进行了其外接氢化物的性质研究，从理论上预测了Ｔｉ８Ｃ１２Ｈ４（Ｔｄ）和Ｔｉ８Ｃ１２Ｈ８（Ｔｄ）几何构型的稳定性和化学反应活性。由Ｔｉ８Ｃ１２（Ｔｄ）和Ｔｉ８Ｃ１２Ｈ８（Ｔｄ）稳定性分析得出：Ｔｉ８Ｃ１２Ｈ４（Ｔｄ）构型最稳定，而Ｔｉ８Ｃ１２Ｈ８（Ｔｄ）和Ｔｉ     

Darstellung und Kristallstruktur von Cs8P8O24 · 8H2O

Synthesis and Crystal Structure of Cs₈P₈O₂₄ · 8H₂O Cs₈P₈O₂₄ · 8H₂O was obtained from Na₈P₈O₂₄ · 6H₂O by cation exchange. Crystal growth was achieved by applying gel techniques (agar agar). The crystal structure (P1 ; a = 766.6(8); b = 1 156.9(9); c = 1 163.4(9) pm; α = 100,2(1)°; β = 106.5(2)°; γ = 92.2(1)°; Z = 1; 4 099 unique diffractometer data; R = 0.051; R(w) = 0.037) contains cyclo-octaphosphate anions with point symmetry C_2h. The cesium atoms are coordinated irregularily by eight and ten oxygen atoms, respectively. The threedimensional linkage of the P₈O₂₄^8?-rings is established via bonds to cesium atoms and hydrogen bonds Provided by H₂O molecules.     

Synthesis of 8-bromo-, 8-methyl- and 8-phenyl-dATP and their polymerase incorporation into DNA

dATP derivatives bearing Br, Me or Ph groups in position 8 were prepared and tested as substrates for DNA polymerases to show that 8-Br-dATP and 8-Me-dATP were efficiently incorporated, while 8-Ph-dATP was a poor substrate due to its bulky Ph group.     

Asymmetric syntheses of (8R,8aS)- and (8R,8aR)-8-hydroxy-5-indolizidinones:Two promising oxygenated indolizidine building blocks

Starting from the oxygenated piperidine building block 20,two synthetic approaches to new building blocks (8R,8aS)-and (8R,8aR)-8-hydroxy-5-indolizidinones 19a/19b and 15a/15b have been developed,respectively. The first one is based on the trans-diastereoselective reductive alkylation (dr = 93:7),followed by a four-step procedure; and the second one called for the RCM reaction on the N,O-acetal derived from a vinylation,which was followed by a pyrrole formation,and a stereocontrolled cis-selective (dr = 91:...     

(8R,8aS)-及(8R,8aR)-8-羟基-5-吲哚里西啶酮的不对称合成:两个有用的羟基吲哚里西啶合成砌块

以3-苄氧基哌啶-2,6-二酮衍生物20为起始原料,分别合成了两类新的合成砌块(8R,8aS)-及(8R,8aR)-8-羟基-5-吲哚里西啶酮19a/19b和15a/15b.19a/19b的合成是基于反式非对映立体选择性还原烷基化反应(dr=93:7),接着经4步转化而成;而化合物15a/15b的制备则以双烯29的RCM反应为关键步骤,再经顺式立体选择性催化氢化(dr=91:9)反应完成.此外,还原化合物15a得到了(8R,8aR)-8-羟基-5-吲哚里西啶18.     

13C NMR spectra of 8-mercaptoquinoline and 8-hydroxyquinoline

The signals in the¹³C NMR spectra of quinoline and its 8-substituted derivatives (SH, SCH₃, OH, OCH₃, NH₂, I, and CH₃), 8,8-diquinolyl disulfide, the 8-hydroxy-N-methylquinolinium ion, and the protonated and anionic forms of 8-hydroxy- and 8-mercaptoquinoline were assigned. The increments of the substituents in the neutral forms of these compounds correlate satisfactorily with those in substituted benzenes and the Swain-Lupton parameters (r = 0.94–0.99). The differences in the ortho increments of the substituents are due to a change in the electron densities on the carbon atoms and also to steric hindrance. The effect of an intramolecular hydrogen bond on the¹³C chemical shift of the quinoline ring of 8-hydroxy- and 8-mercaptoquinoline was examined. The¹³C chemical shifts correlate satisfactorily with the total charges (q) on the carbon atoms in the neutral forms of these compounds. A similar correlation is satisfied to a lesser extent for the protonated and anionic forms because of a change in the bond orders.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 657–662, May, 1980.     

Silicide und Germanide mit Gd6Cu8Ge8-Struktur

Zusammenfassung Die Verbindungen {Sc,Y,Tb,Dy,Ho,Er,Tm,Yb,Lu}₆Cu₈Si₈ sowie {Y,Yb}₆Cu₈Ge₈ werden hergestellt. Diese sind isotyp mit der Gd₆Cu₈Ge₈-Struktur. Die Gitterparameter werden ermittelt.

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Silicides and germanides with Gd₆Cu₈Ge₈-structure type

The compounds {Sc,Y,Tb,Dy,Ho,Er,Tm,Yb,Lu}₆Cu₈Si₈ and {Y,Yb}₆Cu₈Ge₈ have been prepared. They were found to be analogous with the Gd₆Cu₈Ge₈-structure type. The lattice parameters have been determined.

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