Anion Cryptates: Synthesis,Crystal Structures,and Complexation Constants of Fluoride and Chloride Inclusion Complexes of Polyammonium Macrobicyclic Ligands

Three macrobicyclic octamines 1–3 and the macrotricyclic hexadecamine 14 have been synthesized. The octamines 1–3 bind anionic substrates when protonated. The stability constants of the complexes between the protonated forms of the macrobicyclic polyamines and halide anions have been determined by pH-metric measurements. The stability constants in H₂O are very high; 1 in its hexaprotonated form binds F⁻ with high selectivity (selectivity F⁻/Cl⁻ > 10⁸), while 3 exhibits strong stability constants for both F⁻ and Cl⁻. Three X-ray structures have been obtained, one where F⁻ is held inside the cavity of 1 · 6H⁺, one where Cl⁻ is included in 3 · 6H⁺, and 3 · 6H⁺ where the cavity is empty.     

Convergence of Some Greedy Algorithms in Banach Spaces

We consider some theoretical greedy algorithms for approximation in Banach spaces with respect to a general dictionary. We prove convergence of the algorithms for Banach spaces which satisfy certain smoothness assumptions. We compare the algorithms and their rates of convergence when the Banach space is L_p(\mathbbT^d)L_p(\mathbb{T}^d) ($1相似文献   

The preparation,crystal and molecular structure of [MoCl2(NH)O(EtPh2PO)2] the preparation,crystal and molecular structure of [MoCl2(NH)O(EtPh2PO)2]. An example of terminal,nonlinear-imido-coordination

Summary Reaction of MoOCl₃ with Me₃SiN₃ m THF followed by addition of tertiary phosphine oxides, RPO₃(R₃=Ph₃, Ph₂Et, Ph₂Me), gives [MoCl₂(NH)O(OPR₃)₂]. The crystal and molecular structure of the compound has been determined by x-ray diffraction methods. The complex crystallises in the monoclinic space group P2₁ /a with four molecules in a unit cell having dimensions a=15.667(8) Å, b=20.135(9) Å, c=9.726(7) Å and =95.01(1) Å. A total of 3510 reflections were collected by counter techniques using MoK radiation. The structure was refined on 2597 reflections with I > 2.58 (I) by full matrix least squares, using anisotropic temperature factors for all nonhydrogen atoms, to give a final R factor of 0.082. The overall configuration of the distorted octahedral complex istrans-dichloro-cis-bis[ethyl(diphenyl)phosphineoxide]cis-(oxo) imido with the molybdenum formally in the oxidation state (VI). The imido hydrogen has been located, and the Mo-N-H system is nonlinear.     

Observation of two‐dimensional yttrium oxide nanoparticles in mealworm beetles (Tenebrio molitor)

Nanomaterials are being used in medicine, manufacturing and consumer products, but their effects on organisms and the environment are not well understood because of the difficulty in detecting them. Here dual‐energy X‐ray K‐edge subtraction was used to track two‐dimensional yttrium oxide nanoparticles (which can be found in such household objects as color televisions) in adult mealworms (Tenebrio molitor). The insects ingested nanoparticle‐infused feed for different time periods, up to 24 h, and the nanoparticles could then be identified at several locations in the insects' head, thorax and abdomen, mostly within the digestive tract. In time, all particles were excreted.     

Functionalized bis(thiosemicarbazonato) complexes of zinc and copper: synthetic platforms toward site-specific radiopharmaceuticals

Two new types of unsymmetrical bis(thiosemicarbazone) proligands and their neutral zinc(II) and copper(II) complexes have been synthesized. These bifunctional ligands both chelate the metal ions and provide pendent amino groups that can be readily functionalized with biologically active molecules. Functionalization has been demonstrated by the synthesis of three water-soluble glucose conjugates of the new zinc(II) bis(thiosemicarbazonato) complexes, and their copper(II) analogues have been prepared in aqueous solution via transmetalation. A range of techniques including NMR, electron paramagnetic resonance, cyclic voltammetry, high-performance liquid chromatography (HPLC), UV/vis, and fluorescence emission spectroscopy have been used to characterize the complexes. Four compounds, including two zinc(II) complexes, have been characterized by X-ray crystallography. The connectivity and conformation of the glucose conjugates have been assigned by NMR spectroscopy. Time-dependent density functional theory calculations have been used to assign the electronic transitions of the copper(II) bis(thiosemicarbazonato) chromophore. Two copper-64-radiolabeled complexes, including one glucose conjugate, have been prepared and characterized using radio-HPLC, and transmetalation is shown to be a viable method for radiolabeling compounds with copper radionuclides. Preliminary cell washout studies have been performed under normoxic conditions, and the uptake and intracellular distribution have been studied using confocal fluorescence microscopy.     

New bimetallic compounds based on the bis(thiosemicarbazonato) motif

Zinc and copper bis(thiosemicarbazonato) complexes containing more than one metal centre have been prepared with a view to examining their application for molecular imaging. The zinc complexes are fluorescent with excitation and emission at relatively long wavelengths. The dinuclear copper complex undergoes two sequential, quasi-reversible reductions.     

Bifunctional chelators for copper radiopharmaceuticals: the synthesis of [Cu(ATSM)-amino acid] and [Cu(ATSM)-octreotide] conjugates

Two new bifunctional chelators that are derivatives of the bis(thiosemicarbazone) ATSMH(2) proligand have been prepared, one with two phenyl carboxylate substituents on the exocyclic nitrogens (L(1)H(2)) and one with a single phenyl carboxylate (L(2)H(2)). The new ligands have been characterised by NMR spectroscopy, mass spectrometry and in the case of L(1)H(2) by X-ray crystallography. The copper, nickel and zinc complexes of the new ligands have been synthesised and characterised. Electrochemical measurements show that the copper(II) complexes undergo a reversible reduction attributable to a Cu(II)/Cu(I) process. The new proligands have been tethered to the N-alpha-Boc-protected amino acids lysine and ornithine using solution and solid phase methods. The new amino acid conjugates form copper complexes and the complexes have been characterised by mass spectrometry and electronic spectroscopy. The bifunctional chelator L(2)H(2) has been conjugated to the tumour targeting peptide octreotide and the new ATSMH(2)-octreotide conjugate and its copper complex have been characterized by mass spectrometry. These new systems have the potential to be used for new targeted copper radiopharmaceuticals for imaging and therapy.