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81.
《Tetrahedron letters》2019,60(34):150949
It is highly valuable to develop bifunctional chemical fertilizers that can both regulate plant growth and reduce the toxicity of pesticides. Here we report three water-soluble pillar[5]arenes WP5-1, WP5-2 and WP5-3 established as efficient plant growth regulators for wheat to efficiently improve the development of buds and roots in the seedling cultivation stage. Moreover, as macrocyclic hosts for the poisoning herbicide paraquat, WP5-2 and WP5-3 can also be employed to reduce its toxicity based on host–guest interactions, as confirmed by cell viability experiments towards HEK 293 and Raw 264.4 cell lines. 相似文献
82.
《Journal of Coordination Chemistry》2012,65(6):980-995
Nickel(II) complexes of 12-membered macrocyclic ligands with different donating atoms (N2O2, N2S2 and N4) in the macrocyclic ring have been encapsulated in the nanocavity of zeolite-Y by the fexible-ligand method. Nickel(II) complexes with macrocyclic ligands were entrapped in the nanocavity of zeolite-Y by a two-step process in the liquid phase: (i) adsorption of precursor ligand; 1,2-di(o-aminophenyl-, amino, oxo, thio)ethane, N2X2; in the supercages of the Ni(II)–NaY, and (ii) in situ condensation of the Ni(II) precursor complex; [Ni(N2X2)]2+; with glyoxal or biacetyl. The new host–guest nanocatalysts (HGNM), [Ni([R]2-N2X2)]2+–NaY (R = H, CH3; X = NH, O, S), have been characterized by FT-IR, DRS and UV–Vis spectroscopic techniques, XRD and elemental analysis, as well as nitrogen adsorption, and were used for oxidation of cyclohexene with molecular oxygen. 相似文献
83.
Raul Abreu de Assis Simona Bonelli 《Nonlinear Analysis: Real World Applications》2012,13(4):1507-1524
We present a mathematical model of parasite-host interactions inspired by the Maculinea-Myrmica system. Numerical simulations of the model were conducted in order to access the possibility of stable multiple host behavior in the model. Results indicate that multiple host behavior can be observed under natural conditions, although a division of the original parasite population into separate subpopulations, each adapted to one distinct host, is expected. Transitions from single to multiple host behavior are expected to occur if the relative host species abundances change or host’s tolerance increases. Further model development and analysis are required to extend these results. 相似文献
84.
Helmut Ehrenberg P.C. Schmidt R. McSweeney K.C. Mishra 《Journal of solid state chemistry》2006,179(4):968-973
Strontium borophosphate phosphate (Sr6BP5O20, SrBP), activated by divalent europium ions is a bluish-green phosphor emitting in a broad band with the emission peak near 480 nm. In this paper, we report the crystal structure of SrBP determined from an analysis of the X-ray diffraction pattern of a prismatic single crystal (size 60 μm×50 μm×40 μm). This crystal was chosen from undoped phosphor powder samples prepared for this purpose by solid-state reaction. SrBP is observed to crystallize in a body-centered tetragonal lattice with the lattice parameters and , the associated space group being (space group 120). Using the structural data from this study, we have also calculated its electronic structure using the augmented spherical wave method and the local density approximation (LDA). We show the ordering of the electronic states by the density of states (DOS) and the partial DOS plots. The LDA gives a direct optical band gap at the Γ point of about 5 eV. The significance of the crystal structure and associated electronic structure is discussed with respect to maintenance of this phosphor in Hg-discharge lamps. 相似文献
85.
Abstract Understanding the self-assembly of nanoscale metal—ligand clusters is an important research area in supramolecular chemistry, especially, if one wishes to develop a truly predictive design strategy for synthesizing these nanoscale clusters. As the building blocks for forming these clusters have become larger and more complex, spacious clusters have been synthesized which often contain large cavities. These assemblies can house guest molecules which play a previously uncharacterized role in the self-assembly processes. We seek to analyze this role: do these guest molecules act as templates? Are the guest molecules necessary for cluster formation? Does the guest drive cluster assemble by forming a stable host—guest complex with the cluster? Must a truly rational design strategy for forming metal—ligand clusters incorporate the use of templates? The role of guest molecules in the self-assembly of nanoscale coordination clusters is reviewed in this article. 相似文献
86.
JENNIFER J. TURNER & MARGARET M. HARDING 《Supramolecular chemistry》2013,25(5):369-375
The chiral cavities present in 2,3:6,7-dibenzo-9-oxabicyclonona-2,6-diene, dibenzobicyclo[b,f][3.3.1]nona-5a, 6a-diene-6,12-dione, bicyclo[3.3.1]nonane and dibenzobicyclo[b,f],diazocines are reminiscent of Tröger's base, which has been widely used as a molecular cleft in supramolecular chemistry. The synthetic methodology to provide key derivatives for elaboration into new supramolecular structures, efficient resolution methods, the introduction of additional recognition groups and applications in supramolecular chemistry of these structurally related molecular clefts are reviewed. 相似文献
87.
Formation of host–guest complexes with acetic acid and benzoic acid was studied by NMR for amide-based octaazacyclophanes having pendant methyl ester arms; the cyclophanes were tetramethyl 2,9,18,25-tetraoxo-1,4,7,10,17,20,23,26-octaaza[10.10]paracyclophane-4,7,20,23-tetraacetate, its meta-isomer and analogues. Amide NH proton and CH2 proton adjacent to amide C = O in every cyclophane host showed down-field NMR shifts in the presence of the guest acids in CHCl3-d, suggesting the formation of 1:1 complexes in which the carboxyl group of an acid molecule formed two hydrogen bonds with the amide NH and C = O moieties of a host molecule. Since the complex formation competed with the dimerization of the guest acids, the monomer–dimer equilibrium was restudied by NMR and the equilibrium constant was determined to be 330 M? 1 for acetic acid and 518 M? 1 for benzoic acid. By using these values, the formation constants of the host–guest complexes were determined to be 8–51 M? 1. The close contact between the host and guest molecules via hydrogen bonding was consistently confirmed by NMR shifts due to the ring current of aromatic group. 相似文献
88.
Vi T. Nguyen Roger Bishop Donald C. Craig Marcia L. Scudder 《Supramolecular chemistry》2013,25(1):103-107
Abstract Crystallization of dialcohol 4 from benzene yields an inclusion compound whose crystal structure [(C13H24O2)2·(C6H6), P21/c, a 7.918(2), b 13.505(2), c 14.924(5) Å, β 109.30(1)°, Z 2, R 0.069] shows that the host molecules are present as parallel doubly-stranded columns. Each column is constructed from one strand of (+)-, and a second of (-)-, enantiomers of 4. These two chirally pure strands are linked through a continuous chain of hydrogen bonding …O—H…O—H…O—H… to complete the column, and the benzene guests occupy interstitial sites between the parallel columns. 相似文献
89.
2,6—双二苯基膦吡啶银(I)配合物的光谱研究 总被引:1,自引:1,他引:0
利用电子吸收光谱和发射光谱,研究具有光致发光性能的三配位Ag(I)配合物[Ag2(μ-PNP)3](ClO4)2(PNP=2,6-双二苯基膦吡啶)的光谱性质,电子吸收光谱中约260和300nm处的肩峰吸收分别被指定为l→aπ(l代表膦的孤对电子,aπ是苯环的反键轨道)和l→π^*(π^*表示吡啶的π反键轨道)跃迁。室温下受紫外可见光激发,配合物的乙腈溶液显示了发光性质,其发射峰位于525nm,这是由配体激发态引起的。利用吸收和发射光谱,研究了配合物光物理性质在不同客体分子如AuPPh3Cl,AgCF3SO3和[Cu(CH3CN)4](ClO4)存在下光物理性质的改变情况。在配合物中,配体PNP和Ag(I)形成一个空穴,可以结合外来的离子,从而引起光物理性质的改变,这种改变,使[Ag2(μ-PNP)3](ClO4)2可以作为作为客体离子的检测探针或传感器。 相似文献
90.
The LiInW2O8:Eu3+, LiInW2O8:Dy3+ and LiInW2O8:Eu3+/Dy3+ phosphors were synthesized by solid-state reaction and their photoluminescence properties were studied. Under UV excitation, the LiInW2O8:Eu3+ phosphor exhibits an intense red emission whereas the LiInW2O8:Dy3+ and LiInW2O8:Dy3+/Eu3+ phosphors show a white emission. The WO6 octahedra play a major role in the luminescence of the host lattice, characterized by a blue emission under UV excitation. The emission of activator ion results from an efficient energy transfer from the LiInW2O8 host lattice to the Eu3+ and Dy3+ ions. The LiIn0.97Dy3+0.03W2O8 and LiIn0.965 Dy3+0.03Eu3+0.005W2O8 samples, optimized for white emission, are interesting candidates for solid-state lighting applications. 相似文献