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1.
A bis‐branched [3]rotaxane, with two [2]rotaxane arms separated by an oligo(para‐phenylenevinylene) (OPV) fluorophore, was designed and investigated. Each [2]rotaxane arm employed a difluoroboradiaza‐s‐indacene (BODIPY) dye‐functionalized dibenzo[24]crown‐8 macrocycle interlocked onto a dibenzylammonium in the rod part. The chemical structure of the [3]rotaxane was confirmed and characterized by 1H and 13C NMR spectroscopy and high‐resolution ESI mass spectrometry. The photophysical properties of [3]rotaxane and its reference systems were investigated through UV/Vis absorption, fluorescence, and time‐resolved fluorescence spectroscopy. An efficient energy‐transfer process in [3]rotaxane occurred from the OPV donor to the BODIPY acceptor because of the large overlap between the absorption spectrum of the BODIPY moiety and the emission spectrum of the OPV fluorophore; this shows the important potential of this system for designing functional molecular systems.  相似文献   

2.
Mimicking photosynthesis : The concept of light‐harvesting by using a mechanically interlocked [3]rotaxane is developed through synthesis and characterization. Our results provide a new candidate for light‐harvesting systems and also open up the possibility of creating intelligent or controllable energy‐collecting machines (see figure).

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3.
A hydrogen-bonded (H-bonded) amide macrocycle was found to serve as an effective component in the host–guest assembly for a supramolecular chirality transfer process. Circular dichroism (CD) spectroscopy studies showed that the near-planar macrocycle could produce a CD response when combined with three of the twelve L-α-amino acid esters (all cryptochiral molecules) tested as possible guests. The host–guest complexation between the macrocycle and cationic guests was explored using NMR, revealing the presence of a strong affinity involving the multi-point recognition of guests. This was further corroborated by density functional theory (DFT) calculations. The present work proposes a new strategy for amplifying the CD signals of cryptochiral molecules by means of H-bonded macrocycle-based host–guest association, and is expected to be useful in designing supramolecular chiroptical sensing materials.  相似文献   

4.
合成了新型的具有二氯代醌亚胺基的稳定生色杯[4]芳烃。用紫外-可见光谱研究其对碱金属、碱土金属、过渡金属和铀酰离子的络合行为,发现具四个生色取代基的杯[4]芳烃对铀酰离子和铜离子表现出高选择性,同时伴随可见光区的吸收完全消失。这一络合时的颜色变化现象有可能用于分析化学。  相似文献   

5.
Lawsones were transformed into the functionally rich framework of methanodibenzo[a,f]azulenes and methanobenzo[f]azulenes in a single- or two-pot operation through five organocatalytic sequential reactions in very good yields with excellent selectivities. These resultant molecules are basic skeletons of important antibiotics, which highlights the value of this formal intramolecular [3+2]-cycloaddition as a key protocol.  相似文献   

6.
十甲基五元瓜环与几种金属离子配合物的晶体结构   总被引:1,自引:0,他引:1  
合成了3个十甲基五元瓜环(Me10Q[5])分别与铷离子、铈离子水合物相互作用形成的配合物以及四氯锌根离子存在下形成的单晶体,并测定了其单晶结构。3个配合物均形成以Me10Q[5]为“胶囊体”,水分子为“胶囊”芯材,金属离子或水分子为“胶囊盖”的“分子胶囊”结构,并通过配键或氢键组装形成一维超分子链结构实体。  相似文献   

7.
In many EuIII‐based materials, the presence of an intermediate energy level, such as ligand‐to‐metal charge transfer (LMCT) states or defects, that mediates the energy transfer mechanisms can strongly affect the lifetime of the 5D0 state, mainly at near‐resonance (large transfer rates). We present results for the dependence of the 5D0 lifetime on the excitation wavelength for a wide class of EuIII‐based compounds: ionic salts, polyoxometalates (POMs), core/shell inorganic nanoparticles (NPs) and nanotubes, coordination polymers, β‐diketonate complexes, organic–inorganic hybrids, macro‐mesocellular foams, functionalized mesoporous silica, and layered double hydroxides (LDHs). This yet unexplained behavior is successfully modelled by a coupled set of rate equations with seven states, in which the wavelength dependence is simulated by varying the intramolecular energy transfer rates. In addition, the simulations of the rate equations for four‐ and three‐level systems show a strong dependence of the emission lifetime upon the excitation wavelength if near‐resonant non‐radiative energy transfer processes are present, indicating that the proposed scheme can be generalized to other trivalent lanthanide ions, as observed for TbIII/CeIII. Finally, the proper use of lifetime definition in the presence of energy transfer is emphasized.  相似文献   

8.
9,10-Bis[methoxy(trimethylsilyl)methyl]anthracenes (24), synthesized from 9,10-dilithioanthracene (26) and bromomethoxytrimethylsilylmethane (27, 2 equiv), decompose (550-650 degrees C/10(-3) mmHg) carbenically to dibenzo[b,f]pentalene (28, > 48%). 9,10-Anthryldicarbenes 39 or their equivalents convert to pentalene 28 rather than di-peri-cyclobutanthracenes 30 and 31, benzobiphenylene 32, or extended rearrangement products 33-38. Formation of 28 from 24 raises questions with respect to the behavior of 1,3,4,6-cycloheptatetraenyl-1-carbenes 49, 2,4,5,7-cyclooctatetraenylidene 51, 2,5,7-cyclooctatriene-1,4-diylidene 52, 1,2,4,5,7-cyclooctapentaene 53, and bicyclo[4.1.0]heptatrienyl-1-carbenes 54 and to carbon-skeleton and hydrogen rearrangements of anthryldicarbenes 39 and/or their equivalents at various temperatures. 1,5-Bis[methoxy(trimethylsilyl)methyl]anthracenes (25), prepared from 1,5-diiodoanthracene (63) and methoxytrimethylsilylmethylzinc bromide (57, 2 equiv) as catalyzed by PdCl(2)(PPh(3))(2), yield the di-peri-carbenic reaction product 1H,5H-dicyclobuta[de,kl]anthracene (30, > 40%) on pyrolysis at 550-650 degrees C/10(-3) mmHg. Proof of structure and various aspects of the mechanisms of formation of 30 are discussed.  相似文献   

9.
10.
Four coordination compounds, namely [Na(H2O)(H2O)2⊂C40H50N20O10](C6H6O2)2Cl·8H2O (1), [K2(H2O)2(H2O)⊂C40H50N20O10](C6H6O2)2Cl2·7H2O (2), [Rb2(H2O)2(H2O)⊂C40H50N20O10](C6H6O2)2Cl2·7H2O (3) and [Cs(H2O)2(H2O⊂C40H50N20O10)](C6H6O2)2Cl·6H2O (4), were obtained by the reactions of the corresponding alkali metal salts with decamethylcucurbit[5]uril (Me10Q[5]) in the presence of hydroquinone, and their structures were determined by single-crystal X-ray diffraction. The results revealed that in compounds 1 and 4 each Me10Q[5] ligand coordinates one Na+ or Cs+ ion to form a molecular bowl structure, while in compounds 2 and 3 each Me10Q[5] ligand coordinates two K+ or Rb+ ions to form a closed molecular capsule structure, and adjacent molecular capsules bridge each other through water molecules to form 1D coordination polymers. In addition, we found that the coordination distances for the metal ions and the height of the metal ions out-of-portal-plane for the four compounds are in the same order, 1 < 2 < 3 < 4, which is attributed to the fact that the radius of alkali cations is in the order Na+ < K+ < Rb+ < Cs+. Although each portal of Q[6] binds with two alkali cations (not including Cs+), the Q[6]-based alkali cations complexes display similar structural trends.  相似文献   

11.
Reported here are the syntheses, conformational structures, electrochemical properties, and noncovalent anion binding of corona[5]arenes. A (3+2) fragment coupling reaction proceeded efficiently under mild reaction conditions to produce a number of novel heteroatom‐ and methylene‐bridged corona[3]arene[2]tetrazine macrocycles. Selective oxidation of the sulfur atom between two phenylene rings afforded sulfoxide‐ and sulfone‐linked corona[5]arenes in good yields. All corona[5]arenes synthesized adopted similar 1,2,4‐alternate conformational structures, forming pentagonal cavities. The cavity sizes and the electronic properties such as redox potentials, were measured with CV and DPV, and were influenced by the different bridging units. As electron‐deficient macrocycles, the acquired corona[3]arene[2]tetrazines served as highly selective hosts, forming complexes with the hydrogen‐bonded dimer of dihydrogen phosphate through cooperative anion–π interactions.  相似文献   

12.
The properties of [MnMo9O32]6− heteropoly anion (HPA 1), as a macroligand with respect to the lanthanide ions, were studied. The band due to heteronuclear charge transfer Ce(III)4f → Mo(VI)4d was isolated. The crystal structure of heteropoly complex (HPC) [La2(H2O)12 (MnMo9O32)] ⋅ 2H2O (I) was determined (space group B2/n, a = 23.597(2) Å, b = 19.832(1) Å, c = 11.810(1) Å, γ = 132.390(6)°, V = 4083.4(6) Å3, Z = 4, R = 3.4%). In HPC, the [MnMo9O32]6− ligand (HPA 1) is a hexadentate ligand, which provides for coordination with each of the two La3+ ions three terminal O atoms of the cis-MoO2 groups. This HPC is peculiar in its neutrality and in the cis-position of the coordination active centers on the ligand surface. The coordination polyhedron of the La atom (nine-vertex polyhedron) is formed by three terminal O atoms of HPA1 and by six O atoms of water molecules. IR study revealed that the terminal O atoms of the cis-MoO2 groups of a ligand are involved in coordination with La.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 6, 2005, pp. 427–435.Original Russian Text Copyright © 2005 by Gavrilova, Molchanov.  相似文献   

13.
The first conductometric studies for the complexation reactions between alkali metaland silver cations with ethyl p-tert-butylcalix[4]ester in the cone conformation using acetonitrile and methanol in the temperature range 278–303 K are reported. The observed molar conductivities were found to decrease significantly for mole ratios less than unity. The conductivity data were analysed using a computer program based upon 1 : 1 stoichiometry. Stability constants of the resulting 1 : 1 complexes were determined, indicating that the sequence of stability in acetonitrile is Na+ > Li+ > K+. The H0 and S0 values of the calix[4]ester complexation reactions were determined from the temperature dependence of the complexation constants, and their significance are discussed.  相似文献   

14.
15.
The electrochemical behavior of p‐tert‐butyl‐sulfonylcalix[4]arene (SCA) has been investigated by cyclic voltammetry. The results show that there is an irreversible electrochemical oxidative wave when the potential ranges from 0.9 to 1.9 V versus saturated calomel electrode (SCE) in CH2Cl2 at a glassy carbon electrode. The kinetic parameters of the andic wave, such as α,n, ks, D and the diffusion activation energy (Ed), were discussed. In addition, the interaction of SCA with metal ions at the water‐air interface was also discussed by Langmuir‐Blodgett (LB) techniques. The results confirm that the selectivity of SCA as ligand for Pb2+ in monomolecular film is very high by complexation action, which provide the foundation that LB film of SCA modified glassy carbon electrode (GCE) as voltammetric sensor to detect trace amounts of Pb2+.  相似文献   

16.
17.
18.
19.
Intermolecular 1H{19F} NOE experiments have been used to explore the interactions of trifluoroethanol (TFE) with the octapeptide hormone [val5]angiotensin II at temperatures from 5 to 25 degrees C. Circular dichroism spectra indicate that 40% trifluoroethanol has an influence on the conformations of the peptide, probably leading to beta-structures. Diffusion experiments show that the mean hydrodynamic radius of the peptide in 40% trifluoroethanol-water is about 8 A, consistent with significant folding of the peptide in this medium. Distance constraints derived from intramolecular NOESY data along with observed vicinal coupling constants (3JCalphaHNH) were used to develop conformations consistent with available data. Assuming that intermolecular 1H{19F} NOEs are the result of diffusive encounters of TFE and peptide molecules, it is shown that no single conformation is consistent with the experimental values of the sigmaHF cross-relaxation parameters. It is argued that the disagreements between observed and expected values of sigmaHF are the result of formation of long-lived (approximately 0.5 ns) fluoroalcohol-peptide complexes, a conclusion consonant with similar studies of other peptide-fluoroalcohol systems. Complex formation appears to be especially prevalent near the charged amino acid side chains of the hormone.  相似文献   

20.
藉杯芳烃衍生物的识别作用可以实现对金属离子的选择性液膜传输,本文研究了4种新型杯[4]冠醚对5种过渡金属离子(Cu^2 ,Fe^3 ,Co^2 ,Ni^2 ,Zn^2 )的液膜传输行为,发现其中酯型杯[4]冠醚(Ⅲ)对Cu^2 有优良的传输效能,并考察考察了各种因素(包括源相和受相酸度、离子载休Ⅲ的浓度、时间及温度等)的影响,指出载体Ⅲ对C ^2 的传输为H^ 交换机理,并对该过程进行了初步解释。  相似文献   

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