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951.
Crown ether-type macrocycles consisting of an enantiopure biarenol derivative and an oligoethylene glycol were synthesized by the Lewis acid-mediated tandem Claisen rearrangement. This is the first example of the successful application of the tandem Claisen rearrangement to the synthesis of enantiopure macrocyclic biarenol derivatives. The enantiopure macrocyclic biarenols were found to form 1:1 complexes with amino acid salts and to discriminate their chirality. 相似文献
952.
A new, reliable method for the introduction of an amine group at positions 2 or 6 of β-cyclodextrin and permethyl-β-cyclodextrin is described. It involves selective tosylation followed by azide substitution and almost quantitative reduction with triphenylphosphine followed by hydrolysis of the phosphinimine intermediate. 相似文献
953.
Luminescent Di‐ and Trinuclear Boron Complexes Based on Aromatic Iminopyrrolyl Spacer Ligands: Synthesis,Characterization, and Application in OLEDs 下载免费PDF全文
Dr. D. Suresh Dr. Clara S. B. Gomes Patrícia S. Lopes Dr. Cláudia A. Figueira Bruno Ferreira Prof. Pedro T. Gomes Dr. Roberto E. Di Paolo Prof. António L. Maçanita Prof. M. Teresa Duarte Dr. Ana Charas Prof. Jorge Morgado Diogo Vila‐Viçosa Prof. Maria José Calhorda 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(25):9133-9149
New bis‐ and tris(iminopyrrole)‐functionalized linear (1,2‐(HNC4H3‐C(H)?N)2‐C6H4 ( 2 ), 1,3‐(HNC4H3‐C(H)?N)2‐C6H4 ( 3 ), 1,4‐(HNC4H3‐C(H)?N)2‐C6H4 ( 4 ), 4,4′‐(HNC4H3‐C(H)?N)2‐(C6H4‐C6H4) ( 5 ), 1,5‐(HNC4H3C‐(H)?N)2‐C10H6 ( 6 ), 2,6‐(HNC4H3C‐(H)?N)2‐C10H6 ( 7 ), 2,6‐(HNC4H3C‐(H)?N)2‐C14H8 ( 8 )) and star‐shaped (1,3,5‐(HNC4H3‐C(H)?N‐1,4‐C6H4)3‐C6H3 ( 9 )) π‐conjugated molecules were synthesized by the condensation reactions of 2‐formylpyrrole ( 1 ) with several aromatic di‐ and triamines. The corresponding linear diboron chelate complexes (Ph2B[1,3‐bis(iminopyrrolyl)‐phenyl]BPh2 ( 10 ), Ph2B[1,4‐bis(iminopyrrolyl)‐phenyl]BPh2 ( 11 ), Ph2B[4,4′‐bis(iminopyrrolyl)‐biphenyl]BPh2 ( 12 ), Ph2B[1,5‐bis(iminopyrrolyl)‐naphthyl]BPh2 ( 13 ), Ph2B[2,6‐bis(iminopyrrolyl)‐naphthyl]BPh2 ( 14 ), Ph2B[2,6‐bis(iminopyrrolyl)‐anthracenyl]BPh2 ( 15 )) and the star‐shaped triboron complex ([4′,4′′,4′′′‐tris(iminopyrrolyl)‐1,3,5‐triphenylbenzene](BPh2)3 ( 16 )) were obtained in moderate to good yields, by the treatment of 3 – 9 with B(C6H5)3. The ligand precursors are non‐emissive, whereas most of their boron complexes are highly fluorescent; their emission color depends on the π‐conjugation length. The photophysical properties of the luminescent polyboron compounds were measured, showing good solution fluorescence quantum yields ranging from 0.15 to 0.69. DFT and time‐dependent DFT calculations confirmed that molecules 10 and 16 are blue emitters, because only one of the iminopyrrolyl groups becomes planar in the singlet excited state, whereas the second (and third) keeps the same geometry. Compound 13 , in which planarity is not achieved in any of the groups, is poorly emissive. In the other examples ( 11 , 12 , 14 , and 15 ), the LUMO is stabilized, narrowing the gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital (HOMO–LUMO), and the two iminopyrrolyl groups become planar, extending the size of the π‐system, to afford green to yellow emissions. Organic light‐emitting diodes (OLEDs) were fabricated by using the new polyboron complexes and their luminance was found to be in the order of 2400 cd m?2, for single layer devices, increasing to 4400 cd m?2 when a hole‐transporting layer is used. 相似文献
954.
ZHOUXiao-hua LEXue-yi LONGLa-sheng CHENShi 《高等学校化学研究》2005,21(1):119-122
It is important to research the mixed-ligand copper complexes containing bioligands, such as amino acids, nucleic acids and proteins, in exploring the functional mechanism of microelement copper in organism because the reaction of any micronutrient with two or more bioligands in the concentrated bioligands background gives mixed-ligand ternary complexes, which are more stable and related with storage of substance and transportationof metal ions in the life process. 相似文献
955.
The diffusion of liposomes and PL/DNA complexes in mucin and collagen solutions, considered to model ‘in vivo’ colloidal gene delivery vector transport, is studied with FCS. The diffusion of defined liposomes is investigated as a function of particle size, surface charge, and the deviation from the Stokes‐Einstein behavior. In all cases the self‐diffusion coefficient decreases exponentially with polymer concentration. The same surface charge dependence of diffusion is observed in mucin for PL/DNA complexes with either positive or negative excess charge. Incubation of positively‐charged PL/DNA complexes in a natural lung surfactant lipid increases the diffusion coefficients to almost the same as for the negatively‐charged PL/DNA complexes.
956.
X‐ray standing wave (XSW) field generated under Bragg reflection condition in a periodic Mo/Si multilayer structure has been used to determine the concentration and location of various trace element contaminants embedded in different layers of that multilayer structure. We have used intense synchrotron X rays for XSW analysis. It is observed that various trace element impurities such as Cr, Fe, Ni and W get embedded unintentionally in the multilayer structure during the deposition process. Consequences of such impurity incorporation on the optical properties of the multilayer structure are discussed in hard and soft X‐ray regions. Present measurements are important in order to optimize the deposition methods on one hand and to better correlate the measured optical properties of a multilayer structure with theoretical models on the other. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
957.
Yizhen Tang Jingyu Sun Xiujuan Jia Hao Sun Xiumei Pan Rongshun Wang 《Journal of computational chemistry》2010,31(7):1520-1527
The reaction of N2H4 with OH has been investigated by quantum chemical methods. The results show that hydrogen abstraction mechanism is more feasible than substitution mechanism thermodynamically. The calculated rate constants agree with the available experimental data. The calculated results show that the variational effect is small at lower temperature region, while it becomes significant at higher temperature region. On the other hand, the small‐curvature tunneling effect may play an important role in the temperature range 220?3000 K. Moreover, the calculated rate constants show negative temperature dependence at the temperatures below 500 K, which is in accordance with Vaghjiani's report that slightly negative temperature dependence is found over the temperature range of 258?637 K. The mechanism of the major product (N2H3) with OH has also been investigated theoretically to understand the title reaction thoroughly. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010 相似文献
958.
YU Qing CAO Jie LIU Tao WANG Zhi-xiang . College of Chemistry Chemical Engineering Graduate School of the Chinese Academy of Sciences Beijing P. R. China 《高等学校化学研究》2009,25(3)
It is well-known that primary amines form inclusive complexes with crown ethers. This kind of noncova-lently inclusive complexes,exemplified tryptophan complex with 18-crown-6,was studied by combination of two experimental methods,fluorimetry and mass spectrometry,with theoretical calculation. Fluorescence intensity of tryptophan in the absence and the presence of 18-crown-6 in aqueous HAc-NaAc buffer solution at pH=3.73 has been studied by fluorometry. The fluorescence intensity decreases significantly wit... 相似文献
959.
T.S. Singh andSivaprasad Mitra 《Journal of photochemistry and photobiology. B, Biology》2009,96(3):193-200
The knowledge of the formation of bile acid micellar aggregates is of great importance because of the biological significance of these compounds and their pharmacological applications. The intramolecular charge transfer (ICT) fluorescence property of trans-ethyl-p-(dimethylamino) cinnamate is used to study the micelles formed by aggregation of three most important bile acids, viz. cholic acid, deoxycholic acid and chenodeoxycholic acid by steady state and picosecond time-resolved fluorescence spectroscopy. The ICT fluorescence band intensity was found to increase with concomitant blue shift with the addition of bile acids. The blue shift in ICT fluorescence maxima as well as decrease in nonradiative decay constants in presence of bile acids indicate the passage of the probe towards the micro domains formed from the aggregated bile acids. Binding constant of the probe with micelles as well as critical micelle concentration and average polarity parameter of the micellar environments were obtained from the variation of fluorescence intensity on increasing concentration of bile acids in the medium. 相似文献
960.
We report herein a pseudo-crown based fluorescent receptor (1) for the selective detection of Cu2+ cation. Receptor 1 can detect Cu2+ even in 5 μM level in acetonitrile-water (9:1 v/v). Compound 1 is very effective for the detection of Cu2+ amongst the series of metal ions studied (Li+, Na+, K+, Ca2+, Mg2+, Ba2+, Pb2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+ and Mn2+). 相似文献