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101.
Andrew G. Tennyson Dr. Robert J. Ono Todd W. Hudnall Dr. Dimitri M. Khramov Dr. Joyce A. V. Er Justin W. Kamplain Dr. Vincent M. Lynch Dr. Jonathan L. Sessler Prof. Christopher W. Bielawski Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(1):304-315
Reaction of bromanil with N,N′‐dimesitylformamidine followed by deprotonation with NaN(SiMe3)2 afforded 1,1′,3,3′‐tetramesitylquinobis(imidazolylidene) ( 1 ), a bis(N‐heterocyclic carbene) (NHC) with two NHC moieties connected by a redox active p‐quinone residue, in 72 % yield of isolated compound. Bimetallic complexes of 1 were prepared by coupling to FcN3 ( 2 ) or FcNCS ( 3 ; Fc=ferrocenyl) or coordination to [M(cod)Cl] ( 4 a or 4 b , where M=Rh or Ir, respectively; cod=1,5‐cyclooctadiene). Treatment of 4 a and 4 b with excess CO(g) afforded the corresponding [M(CO)2Cl] complexes 5 a and 5 b , respectively. Analysis of 2 – 5 by NMR spectroscopy and X‐ray diffraction indicated that the electron‐deficient quinone did not significantly affect the inherent spectral properties or coordination chemistry of the flanking imidazolylidene units, as compared to analogous NHCs. Infrared spectroscopy and cyclic voltammetry revealed that decreasing the electron density at MLn afforded an increase in the stretching energy and a decrease in the reduction potential of the quinone, indicative of metal–quinone electronic interaction. Differential pulse voltammetry and chronoamperometry of the metal‐centered oxidations in 2 – 4 revealed two single, one‐electron peaks. Thus, the metal atoms bound to 1 are oxidized at indistinguishable potentials and do not appear electronically coupled. However, the metal–quinone interaction was used to increase the electron density at coordinated metal atoms. Infrared spectroelectrochemistry revealed that the average νCO values for 5 a and 5 b decreased by 14 and 15 cm?1, respectively, upon reduction of the quinone embedded within 1 . These shifts correspond to 10 and 12 cm?1 decreases in the Tolman electronic parameter of this ditopic ligand. 相似文献
102.
Er‐Lei Yang Yun‐Liang Jiang Yu‐Ling Wang Qing‐Yan Liu 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(9):m231-m234
The title compound, {[Cd2(C10H12N2O8)(H2O)]·H2O}n, consists of two crystallographically independent CdII cations, one ethylenediaminetetraacetate (edta) tetraanion, one coordinated water molecule and one solvent water molecule. The coordination of one of the Cd atoms, Cd1, is composed of five O atoms and two N atoms from two tetraanionic edta ligands in a distorted pentagonal–bipyramidal coordination geometry. The other Cd atom, Cd2, is six‐coordinated by five carboxylate O atoms from five edta ligands and one water molecule in a distorted octahedral geometry. Two neighbouring Cd1 atoms are bridged by a pair of carboxylate O atoms to form a centrosymmetric [Cd2(edta)2]4− unit located on the inversion centre, which is further extended into a two‐dimensional layered structure through Cd2—O bonds. There are hydrogen bonds between the coordinated water molecules and carboxylate O atoms within the layer. The solvent water molecules occupy the space between the layers and interact with the host layers through O—H...O and C—H...O interactions. 相似文献
103.
104.
Let F be a field with characteristic 0, V = Fn the n-dimensional vector space over F and let G be a finite pseudo-reflection group which acts on V . Let χ : G→ F* be a 1- dimensional representation of G. In this article we show that χ(g) = (detg)α(0 ≤ α ≤ r - 1), where g ∈ G and r is the order of g. In addition, we characterize the relation between the relative invariants and the invariants of the group G, and then we use Molien’s Theorem of invariants to compute the Poincar′e series of relative invariants. 相似文献
105.
Quasiperiodic solutions of degenerate linear systems of second-order ordinary differential equations
We establish sufficient conditions for the existence of quasiperiodic solutions of a system of ordinary second-order differential
equations with degenerate symmetric matrix of the second derivatives for an arbitrary quasiperiodic inhomogeneity. 相似文献
106.
Jeong SC Herrmann N Fan ZG Freifelder R Gobbi A Hildenbrand KD Krämer M Randrup J Reisdorf W Schüll D Sodan U Teh K Wessels JP Pelte D Trzaska M Wienold T Alard JP Amouroux V Basrak Z Bastid N Belayev IM Berger L Bini M Blaich T Boussange S Buta A Caplar R Cerruti C Cindro N Coffin JP Dona R Dupieux P Erö J Fintz P Fodor Z Fraysse L Frolov S Grigorian Y Guillaume G Hölbling S Houari A Jundt F Kecskemeti J Koncz P Korchagin Y Kotte R Kuhn C Ibnouzahir M Legrand I Lebedev A Maguire C Manko V 《Physical review letters》1994,72(22):3468-3471
107.
Göczõ H Szabó-Révész P Farkas B Hasznos-Nezdei M Serwanis SF Pintye-Hódi AK Kása P Erõs I Antal I Marto S 《Chemical & pharmaceutical bulletin》2000,48(12):1877-1881
The production of spherical crystals has recently gained great attention due to the fact that the crystal habit (form, surface, size, etc.) can be modified during the crystallization process. Spherical crystals of ASA were developed by non-typical and typical spherical crystallization techniques. The non-typical spherical crystallization process (conventional stirred tank method) resulted in few monocrystals and non-spherical crystal agglomerates. The typical spherical crystallization process was carried out by the three solvent-system (ethanol-water-carbon tetrachloride). The products were qualified by morphological study, NIR investigation, salicylic acid content, dissolution rate, studies on flowability, compactibility, cohesivity and tablettability. The results demonstrate that only typical spherical crystallization can be recommended for the production of spherical crystals of ASA. Only product made by this technique shows excellent flow properties and favourable compactibility, cohesiveness and tablettability values. 相似文献
108.
A highly stereoselective route to the polysubstituted chiral octahydrobenzofuran 12 , a potential synthon for the E‐ring core in the (?)‐reserpine synthesis, is described. The α‐bromo acetal 11 was obtained from inexpensive (?)‐shikimic acid ( 3 ) through a series of highly stereoselective chemical reactions (Scheme). Et3B/Bu3SnH‐Mediated intramolecular radical cyclization of 11 led to compound 12 with the required configuration. 相似文献
109.
Synthesis of a Functional Aluminium Alkynide, Me3C‐C≡C‐AlBr2, and its Reactions with the Bulky Lithium Compound LiCH(SiMe3)2 Treatment of aluminium tribromide with the lithium alkynide (Li)C≡C‐CMe3 afforded the aluminium alkynide Me3C‐C≡C‐AlBr2 ( 1 ) in an almost quantitative yield. 1 crystallizes with trimeric formula units possessing Al3C3 heterocycles and the anionic carbon atoms of the alkynido groups in the bridging positions. A dynamic equilibrium was determined in solution which probably comprises trimeric and dimeric formula units. Reaction of 1 with one equivalent of LiCH(SiMe3)2 yielded the compound [Me3C‐C≡C‐Al(Br)‐CH(SiMe3)2]2 ( 2 ), which is a dimer via Al‐C‐Al bridges. Two equivalents of the lithium compound gave a mixture of four main‐products, which could be identified as 2 , Li[Me3C‐C≡C‐Al{CH(SiMe3)2}3] ( 3 ), Me3C‐C≡C‐Al[CH(SiMe3)2]2 ( 4 ), and Al[CH(SiMe3)2]3. The lithium atom of 3 is coordinated by the C≡C triple bond and an inner carbon atom of one bis(trimethylsilyl)methyl group. Further interactions were observed to C‐H bonds of methyl groups. 相似文献
110.
应用相对论有效核势密度泛函理论计算方法研究了Cun-和CunCO-簇的平衡几何构型、稳定性、主要碎片化模式、CO吸附能及其团簇的光谱性质.计算结果表明,奇数簇Cun-的电离势比其相邻偶数簇Cun-的电离势大;奇数的Cu5CO-簇有最大的CO解离能.奇数铜簇阴离子相对较高的稳定性与近似浆汁模型的8电子电子闭壳层效应一致.计算得到的Cun-簇碎片化能量表明,较小Cun-的优势解离通道与其包含Cu原子数目的奇偶性有关,偶数的Cun-簇主要解离为Cu原子和Cun-1-,而奇数Cun-簇易以解离成铜的二聚物Cu2和Cun-2-.基于密度泛函理论计算,讨论了这些簇的静态极化率和CO吸附性质与簇大小的关系. 相似文献