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771.
Hung Banh Katharina Dilchert Christine Schulz Dr. Christian Gemel Dr. Rüdiger W. Seidel Dr. Régis Gautier Dr. Samia Kahlal Prof. Dr. Jean‐Yves Saillard Prof. Dr. Roland A. Fischer 《Angewandte Chemie (International ed. in English)》2016,55(10):3285-3289
The bottom‐up synthesis of organometallic zinc clusters is described. The cation {[Zn10](Cp*)6Me}+ ( 1 ) is obtained by reacting [Zn2Cp*2] with [FeCp2][BAr4F] in the presence of ZnMe2. In the presence of suitable ligands, the high reactivity of 1 enables the controlled abstraction of single Zn units, providing access to the lower‐nuclearity clusters {[Zn9](Cp*)6} ( 2 ) and {[Zn8](Cp*)5(tBuNC)3}+ ( 3 ). According to DFT calculations, 1 and 2 can be described as closed‐shell species that are electron‐deficient in terms of the Wade–Mingos rules because the apical ZnCp* units that constitute the cluster cage do not have three, but only one, frontier orbitals available for cluster bonding. Zinc behaves flexibly in building the skeletal metal–metal bonds, sometimes providing one major frontier orbital (like Group 11 metals) and sometimes providing three frontier orbitals (like Group 13 elements). 相似文献
772.
Anion‐ and Solvent‐Induced Assembly and Reversible Structural Transformation of d10‐Metal Coordination Architectures Containing N‐(4‐(4‐Aminophenyloxy)phenyl)isonicotinamide
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Prof. Biing‐Chiau Tzeng Yu‐Ching Hung Dr. Gene‐Hsiang Lee 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(4):1522-1530
We set out studies on anion‐ and solvent‐induced assembly based on the ligand N‐(4‐(4‐aminophenyloxy)phenyl)isonicotinamide (papoa), which is synthesized to show a bent and flexible backbone. Reactions of papoa with ZnX2 (X=Cl, Br, and I) gave the dinuclear macrocycles ([ZnX2(papoa)]2; X=Cl ( 1 a ), Br ( 2 a ), I ( 3 )), the structure of which was determined by X‐ray diffraction. Notably, the less bulky Cl and Br compounds afforded the coordinated imine in acetone (i.e., [ZnX2(papoi)]2, papoi=N‐(4‐(4‐(propan‐2‐ylideneamino)phenoxy)phenyl)isonicotinamide; X=Cl ( 1 b ), Br ( 2 b )), whereas the iodine one only gave the coordinated amine compound 3 under the same reaction condition. In fact, the coordinated imine can return to the amine analogue upon exposure to air or in DMSO, which has been monitored by 1H NMR spectroscopy and powder X‐ray diffraction. Both the dinuclear [Zn(papoa)(NO3)2]2 ( 4 a ) and the 1D [Zn(papoa)2(NO3)2]n ( 4 b ) were formed from the reaction of Zn(NO3)2 and papoa in mixed solvents with acetone and acetonitrile, respectively. In addition, Cd(ClO4)2 can react with papoa to give the 1D framework {[Cd(papoa)2(CH3CN)2](ClO4)2}n ( 5 a ) and the 2D framework [Cd(papoa)2(ClO4)2]n ( 5 b ), depending on the solvent used, that is, MeOH and CH3CN, respectively. Importantly, the 1D framework with axially coordinated CH3CN molecules and the 2D framework with axially coordinated ClO4? ions can be interconverted by heating and grinding in the presence of CH3CN, respectively. Such a reversible structural transformation process was proven by PXRD studies. 相似文献
773.
Tunable Photochromism in the Robust Dithienylethene‐Containing Phospholes: Design,Synthesis, Characterization,Electrochemistry, Photophysics,and Photochromic Studies
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Dr. Jacky Chi‐Hung Chan Dr. Hok‐Lai Wong Prof. Dr. Wing‐Tak Wong Prof. Dr. Vivian Wing‐Wah Yam 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(18):6936-6948
A series of dithienylethene‐containing phosphole derivatives has been designed, synthesized and characterized. One of the compounds has been characterized by X‐ray crystallography. Upon photoexcitation, the compounds exhibit drastic color changes, ascribed to the reversible photochromic behavior. Their photochromic, photophysical and electrochemical properties have been studied. They show photochromic reactivities with high photocyclization quantum yields. Their photophysical and photochromic properties are found to be facilely tuned in this system by substitution at the phosphole backbone, as well as variation on the extent of π‐conjugation of the phosphole backbone. Some selected compounds have been demonstrated to exhibit photochromic properties in polymethylmethacrylate (PMMA) films. 相似文献
774.
We consider homogenization for weakly coupled systems of Hamilton–Jacobi equations with fast switching rates. The fast switching rate terms force the solutions to converge to the same limit, which is a solution of the effective equation. We discover the appearance of the initial layers, which appear naturally when we consider the systems with different initial data and analyze them rigorously. In particular, we obtain matched asymptotic solutions of the systems and the rate of convergence. We also investigate properties of the effective Hamiltonian of weakly coupled systems and show some examples which do not appear in the context of single equations. 相似文献
775.
776.
A purification procedure is described for preparing a heavy metal-removed blank seawater without altering its major compositions and pH. Coastal seawater is treated sequentially by passing through a charcoal column, shaking with a dense slurry of ferric hydroxide at pH 8, and passing the surpernatant through a Chelex-100 chelating ion-exchange column. Experimental data show that this process efficiently removes Cd, Co, Cu, Cr(III), Fe, Mn, Ni, Pb, V and Zn from natural seawater at the spiking concentrations of 10 and 100 ppb levels. 相似文献
777.
N. D. Hung Y. Segawa Y. H. Meyer P. Long L. H. Hai 《Applied physics. B, Lasers and optics》1996,62(5):449-455
Diffraction and transform-limited picosecond tunable pulses are generated from Spectro-temporal-Selection (STS) dye lasers by using a new extra-cavity filter. This filter is based on a grazing-incident grating and arranged in the configuration of a folded dispersive delay line. Thus, it provides both high spectral selectivity and controllable temporal compensation for elimination of pulse broadening. Direct production of diffraction- and transform-limited picosecond dye laser (10 µJ, 50 ps) pulses spectrally adjustable between 398 and 702 nm is demonstrated in a compact device, with 8 ns pump pulses from a nanosecond nitrogen laser. 相似文献
778.
A. Wang D. Weinstein L. Greenfield L. Chiu R. Chambers C. Stewart G. Hung F. Diaz T. Ellis 《Magnetic resonance imaging》1990,8(6):805-809
The role of magnetic resonance imaging and plain radiographs in evaluating osteomyelitis in the diabetic foot was studied. Fifty patients were prospectively examined by magnetic resonance imaging and plain radiographs to determine the extent of infection. Thirty-seven patients had positive MRI for osteomyelitis and 19 were positive with conventional radiography. Thirteen patients had negative MRI healed with short course of antibiotics. Five patients with positive MRI received four weeks' course of intravenous antibiotics with two still having persistent infection in the six weeks follow-up. Thirty-two patients underwent surgery with favorable results. Sixty-two bone specimens were obtained for histologic evaluation of osteomyelitis. In cases with histologic proof of diagnosis, magnetic resonance sensitivity was 99%, specificity was 81%, and accuracy was 94%. Thus magnetic resonance imaging was shown to have a high sensitivity, specificity, and accuracy in detecting osteomyelitis. 相似文献
779.
780.