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排序方式: 共有288条查询结果,搜索用时 62 毫秒
111.
In recent years, semiconducting polymer dots (Pdots) have emerged as a new type of ultrabright fluorescent probes, which have been proved to be very useful for biomedical imaging. Pdots possess several exceptional advantages including high fluorescence brightness, fast radiative rate, excellent photostability, and negligible cytotoxicity. Among these new types of Pdots, the near‐infrared (NIR) fluorescent Pdots appear to be the most urgent and important owing to their promising deep‐tissue imaging in the clinic. This mini‐review highlights the recent progress in the design of NIR‐emitting Pdots and their biomedical applications both in vitro and in vivo. 相似文献
112.
Bo‐Syuan Jhong Ting‐Yu Lin Chien‐Hsiang Kao Hsi‐Jung Yu Tsung‐Mei Chin Ching‐Yang Liu Yuh‐Chiang Shen Ming‐Jaw Don 《中国化学会会志》2019,66(4):409-414
An efficient method to synthesize morachalcones B and C ( 1 and 2 ) is described. Rap?Stoermer condensation and 1,3‐prenyl rearrangement were used as two key synthetic methods. Morachalcone C was obtained by photo‐oxygenation of morachalcone B. Morachalcones B and C showed moderate anti‐inflammatory activity. 相似文献
113.
Chun‐Hsu Yen Yi‐Deng Lin Hsiang‐Wen Hsueh Yun‐Jen Shieh Pei‐Fang Wu Ting‐Shen Kuo Yi‐Chou Tsai 《中国化学会会志》2019,66(9):1048-1063
A new family of the quintuply bonded dichromium complexes [Cr2{μ‐κ2‐HC(N‐2,6‐R2C6H3)2}2(μ‐κ2‐HC[NAr]2)] (R = iPr, Ar = 4‐MeC6H4 ( 5 ), Ar = 3,5‐Me2C6H3 ( 6 ), and Ar = 2,6‐Me2C6H3 ( 7 ); R = Et, Ar = 4‐MeC6H4 ( 8 ), Ar = 3,5‐Me2C6H3 [ 9 ], and Ar = 2,6‐Et2C6H3 ( 10 )) with a heteroleptic lantern configuration was obtained upon the addition of one equivalent of amidinate to the quintuply bonded dichromium amidinates [Cr{μ‐κ2‐HC(N‐2,6‐R2C6H3)2}]2 (R = iPr, Et). Additionally, the same approach was applied to the preparation of the acetate derivative [Cr2{μ‐κ2‐HC(N‐2,6‐ iPr2C6H3)2}2(μ‐κ2‐CH3CO2)] ( 11 ), which represents the first example that the quintuply bonded dinuclear complex contains an oxygen‐containing ligand. Of particular interest is that the Cr‐Cr bond lengths in these new trigonal paddlewheel quintuple Cr‐Cr bond species are comparable with those in their precursor compounds. They show ultrashort Cr‐Cr bond lengths in a narrow range of 1.740–1.755 å on the basis of single‐crystal X‐ray crystallography. The small Mayer bond orders of the long Cr‐N bonds as well as divergent, C2v and D3h, structural conformations in 5 – 11 suggest that the metal–ligand interactions possess minor covalent character and the electrostatic interactions play a dominant role. As a result, these extremely short Cr‐Cr quintuple bonds are caused by the overlap between five pairs of d orbitals that do not involve much in metal–ligand bonding. Additionally, anionic lantern dichromium trisamidinates 5 – 10 can be chemically oxidized by one electron, supported by electrochemistry, and their ease to undergo oxidation is presumably associated with their neutral lantern dichromium trisamindinate products, whose structures inherently display a Jahn‐Teller distortion, exemplified by the structure of the homoleptic dichromium complex [Cr2{μ‐κ2‐HC(N‐2,6‐Et2C6H3)2}3] [ 12 ] determined by X‐ray crystallography. These results unambiguously support the Cr‐Cr quintuple bonding in these novel anionic lantern dichromium complexes. 相似文献
114.
Hsiang‐Chun Chang Jia‐Qi Li Ching‐Kai Lin Yu‐Jung Hsu Tsung‐Han Tu Yi‐Liang Hsieh Hsiu‐Hao Hsu Gene‐Hsiang Lee Yi‐Hung Liu Chi‐How Peng 《中国化学会会志》2019,66(9):1119-1133
Poly(di(pyridin‐2‐yl)methyl acrylate) (PDPyMA), which was obtained by the free radical polymerization of designed coordinative monomer of di(pyridin‐2‐yl)methyl acrylate, is able to coordinate with various metal ions to form heterogeneous catalysts for diverse catalytic reactions. The Pd and Cu complexes supported by PDPyMA were developed for the heterogeneous Suzuki‐Miyaura reaction and Friedel‐Crafts alkylation, respectively. The PDPyMA‐based catalysts showed no significant decline of reactivity after five times recycling. However, the hydrolysis of the PDPyMA backbone under alkaline conditions limited the catalytic efficiency of this heterogeneous catalyst so that the coordinative monomer was redesigned as 1,1‐di(pyridine‐2‐yl)‐2‐(4‐vinylphenyl)ethan‐1‐ol and then 2,2′‐(1‐methoxy‐2‐(4‐vinylphenyl)ethane‐1,1‐diyl)dipyridine (MVPhDPy). With copolymerization of N‐isopropyl acrylamide (NIPAM), the efficiency of polymer‐based heterogeneous catalysts could be further raised, demonstrated by the increased turn over number in the Suzuki‐Miyaura reaction, which approached 5,260 by using the catalyst formed from poly(MVPhDPy‐co‐NIPAM) and Pd(OAc)2. poly(MVPhDPy‐co‐NIPAM) copolymer, therefore, could be a versatile platform to support different metal ions for various heterogeneous catalytic reactions. 相似文献
115.
Thermodynamic uncertainty principles make up one of the few rare anchors in the largely uncharted waters of nonequilibrium systems, the fluctuation theorems being the more familiar. In this work we aim to trace the uncertainties of thermodynamic quantities in nonequilibrium systems to their quantum origins, namely, to the quantum uncertainty principles. Our results enable us to make this categorical statement: For Gaussian systems, thermodynamic functions are functionals of the Robertson-Schrödinger uncertainty function, which is always non-negative for quantum systems, but not necessarily so for classical systems. Here, quantum refers to noncommutativity of the canonical operator pairs. From the nonequilibrium free energy, we succeeded in deriving several inequalities between certain thermodynamic quantities. They assume the same forms as those in conventional thermodynamics, but these are nonequilibrium in nature and they hold for all times and at strong coupling. In addition we show that a fluctuation-dissipation inequality exists at all times in the nonequilibrium dynamics of the system. For nonequilibrium systems which relax to an equilibrium state at late times, this fluctuation-dissipation inequality leads to the Robertson-Schrödinger uncertainty principle with the help of the Cauchy-Schwarz inequality. This work provides the microscopic quantum basis to certain important thermodynamic properties of macroscopic nonequilibrium systems. 相似文献
116.
Thermodynamic uncertainty relations (TURs) represent one of the few broad-based and fundamental relations in our toolbox for tackling the thermodynamics of nonequilibrium systems. One form of TUR quantifies the minimal energetic cost of achieving a certain precision in determining a nonequilibrium current. In this initial stage of our research program, our goal is to provide the quantum theoretical basis of TURs using microphysics models of linear open quantum systems where it is possible to obtain exact solutions. In paper [Dong et al., Entropy 2022, 24, 870], we show how TURs are rooted in the quantum uncertainty principles and the fluctuation–dissipation inequalities (FDI) under fully nonequilibrium conditions. In this paper, we shift our attention from the quantum basis to the thermal manifests. Using a microscopic model for the bath’s spectral density in quantum Brownian motion studies, we formulate a “thermal” FDI in the quantum nonequilibrium dynamics which is valid at high temperatures. This brings the quantum TURs we derive here to the classical domain and can thus be compared with some popular forms of TURs. In the thermal-energy-dominated regimes, our FDIs provide better estimates on the uncertainty of thermodynamic quantities. Our treatment includes full back-action from the environment onto the system. As a concrete example of the generalized current, we examine the energy flux or power entering the Brownian particle and find an exact expression of the corresponding current–current correlations. In so doing, we show that the statistical properties of the bath and the causality of the system+bath interaction both enter into the TURs obeyed by the thermodynamic quantities. 相似文献
117.
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
118.
A systematic limit cycle suppression method is presented to predict and suppress the sustained limit cycles persisting in
a class of uncertain control systems containing inherent nonlinearity. The aim is to determine the feasible controller parameter
sets in the parameter plane for the entire uncertain system. A family of constant limit cycle amplitude loci is plotted. Successful
application to pitch orientation control system with parametric uncertainties and nonlinearity is demonstrated. System output
response is further investigated. 相似文献
119.
120.