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81.
A Pyrex glass capillary (0.4 mm internal diameter) microreactor was developed and used for Suzuki coupling reactions. Capillary-microreactors are more attractive than photolithographic microfluidic devices in terms of simplicity, low cost and ease of handling. Compared with the conventional synthesis procedure, our approach of using a capillary-microreactor offers a convenient and highly efficient means to optimize reaction conditions and the performance of catalysts. The procedure exhibits good precision, reproducibility and high reaction yield for a range of reactants investigated. 相似文献
82.
A simple aliphatic dipeptide, l-leucyl-l-alanine (Leu-Ala), includes several alkyl methyl sulfoxides enantioselectively to form inclusion crystals. From single-crystal X-ray analyses of three inclusion compounds of dimethyl sulfoxide (DMSO), isobutyl methyl sulfoxide, and benzyl methyl sulfoxide, it was elucidated that Leu-Ala molecules self-assemble to form layer structures and the sulfoxides are included via hydrogen bonding in a cavity between these layers. The inclusion cavity has methyl group and isobutyl group at its each side, and the guest sulfoxide is placed in such a manner that its methyl group faces toward the methyl of the Leu-Ala cavity. When the alkyl group of the sulfoxide is comparably large, it is located in the residual space of the cavity to attain effective crystal packing. Thus, the sulfoxides having a comparably large group such as isobutyl, butyl, and benzyl are included with a high (R)-enantioselectivity in Leu-Ala crystals. 相似文献
83.
以分子基材料为目标的功能配合物的设计合成是近年来材料化学研究的重要领域,传统的分子设计尽管在分子水平上获得了很大的成功,但在由分子到晶体,由微观性质到宏观功能的晶体工程研究中遇到了极大的困难。因为宏观功能不仅要求分子本身具有良好的性能,同时还要求分子按照一定的方式堆积和排列犤1~3犦。例如二阶非线性光学材料不但要求分子具备较大的非线性超极化率和非对称中心,而且还要求分子在堆积过程中形成无心空间群的晶体。而自然界中大约超过70%的手性分子在结晶时都形成有心的空间群,因此,如何实现分子的无心堆积是非… 相似文献
84.
Adachi K Sugiyama Y Yoneda K Yamada K Nozaki K Fuyuhiro A Kawata S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(22):6616-6628
Novel triply hydrogen bonded suprastructures based on [M(tdpd)2(L)2]2- (H2tdpd=1,4,5,6-tetrahydro-5,6-dioxo-2,3-pyrazinedicarbonitrile, L=solvent) and melamine-analogous cations have been synthesized and characterized. The use of anions containing two AAA sets from [M(tdpd)2(L)2]2- together with cations containing one DDD set (A=hydrogen-bond acceptor, D=hydrogen-bond donor) leads to the formation of complementary triply hydrogen bonded modules in the solid state. In all cases, the building module is further extended via additional hydrogen-bonding interactions to produce a tape, and tapes are assembled into sheets. These results show that a hydrogen-bonded module consisting of different kinds of building blocks, one of which is a metal complex that includes hydrogen-bond acceptor sites and the other is a hydrogen-bond donor molecule, will be attractive for constructing metal-containing supramolecular systems by the self-assembly technique. 相似文献
85.
Ryo HorikoshiTomoyuki Mochida Hiroshi Moriyama 《Journal of solid state chemistry》2002,164(2):320-325
A series of ionic 4-(4′-pyridylthio)-1-methylpyridinium salts with different counteranions (1, I−; 2, BF−4; 3, PF−6; and 4, OTf−, where OTf=trifluoromethanesulfonate) have been prepared. Structural analysis reveals that the cation exhibits a variety of stacking structures dependent on the anion. Compound 1 crystallizes in space group P21/n (#14), with a=10.764(3) Å, b=9.601(5) Å, c=13.105(3) Å, β=108.35(2), V=1285.4(8) Å3, and Z=4. In this compound, each cation moiety is stacked in a helical arrangement along the c-axis. Compound 2, which is isomorphous to 1, has space group P21/n (#14), with a=11.647(2) Å, b=9.203(3) Å, c=13.232(2) Å, β=108.42(2), V=1345.6(5) Å3, and Z=4. Compound 3 crystallizes in space group P21/n (#14), with a=8.06(1) Å, b=17.43(1) Å, c=10.30(1) Å, β=103.0(1), V=1410(3) Å3, and Z=4. In this salt, the cation molecules assume a head-to-tail stacking arrangement, forming a polar pseudo 1-D chain. Compound 4 crystallizes in space group Pb? (#2), with a=7.585(4) Å, b=15.443(7) Å, c=6.775(4) Å, α=99.33(4), β=108.35(2)o, γ=98.37(4), V=756.6(7) Å3, and Z=2. The structure of 4 consists of a columnar stacking of pyridine moieties, with the cation moieties surrounded by the counteranions. Calculations show that the 4-(4′-pyridylthio)-1-methylpyridinium cation may be a good building block for second harmonic generation (SHG) materials, even though salts 1-4 crystallized in centrosymmetric structures and were SHG inactive. 相似文献
86.
87.
Alicia Reyes-Arellano Roland Boese Ingo Steller Reiner Sustmann 《Structural chemistry》1995,6(6):391-396
The crystal structures of molecular complexes betweenmeso- 1,2-diphenyl-1,2-ethanediol and two bisimines (N,N-(dibenzylidene)-ethylenediamine and glyoxylidene-bis(2,4-dimethyl-3-pentyl-amine) are reported at different temperatures. The structure-determining motif of the cocrystalline arrangement is one single O-H . N hydrogen bond resulting in infinite ladderlike polymers. The supramolecular structure is formed by recognition of fitting species: Thed- orl-isomers do not arrange in such structures.1H NMR experiments show that no prearrangements take place by forming complexes in solution. 相似文献
88.
Based on building emerging engineering education of "energy chemistry", we investigated the state key petro-chemical enterprises according to the industrial development and the demand of professional talents. The research report summarizes, analyzes and discusses the current priority development fields of industry, the talent training status, curriculum structure and education program of the chemistry and chemical engineering in universities. The ideas on emerging engineering education of "energy chemistry" have been proposed, and it will be beneficial to building a novel education program for talents training, which integrates the principle of chemistry, energy conversion and information science, etc. 相似文献
89.
The protolytic equilibria of piperazine (C4H10N2) and phosphate have been investigated in the presence of cobalt or nickel chloride or nitrate by potentiometric titrations between pH 2 and 8. Potentiometric titrations suggest the presence of [M2+(H2O)5(C4H11N2+)]3+ and [M2+(H2O)5(C4H10N2)]2+ in solution with stability constants logK of 3.1 and 3.8 for M = Co and 3.1 and 3.6 for M = Ni, respectively. Crystallization experiments were then conducted at selected pH values to isolate desired species from the known solution composition. Crystallization afforded [M(H2O)6]2+(C4H12N22+)(HPO42—)2 at pH 3.5 and 6.2 (M = Co, Ni), and Co3(PO4)2·8H2O at pH 10.5. No crystals with the dihydrogenphosphate anion or a metal‐bound piperazine ligand could be isolated under the reaction conditions. The solid‐state assembly in the isomorphous structures of [M(H2O)6](C4H12N2)(HPO4)2 with M = Co and Ni is based on an extended hydrogen bonded network between the three ionic building blocks. 相似文献
90.
Carvajal MA Alvarez S Novoa JJ 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(9):2117-2132
The nature of intermolecular interactions between dicoordinate Cu(I) ions is analyzed by means of combined theoretical and structural database studies. Energetically stable Cu(I).Cu(I) interactions are only found when the two monomers involved in the interaction are neutral or carry opposite charges, thus allowing us to speak of bonding between the components of the bimolecular aggregate. A perturbative evaluation of the components of the intermolecular interaction energies, by means the IMPT scheme of Stone, indicates that both the Coulombic and dispersion forces are important in determining the Cu(I).Cu(I) bonding interactions, because only a small part of that energy is attributable to Cu.Cu interactions, while a large component results from Cu.ligand interactions. The electrostatic component is the dominant one by far in the interaction between charged monomers, while in the interaction between neutral complexes, the electrostatic component is found to be of the same order of magnitude as the dispersion term. Bimolecular aggregates that have like charges are repulsive by themselves, and their presence in the solid state results from anion.cation interactions with ions external to this aggregate. In these cases, the short-contact Cu.Cu interactions here should be more properly called counterion-mediated Cu.Cu bonds. 相似文献