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21.
A donor-acceptor compound based on N,N,N',N'-tetramethyl-p-phenylene-diamine and 1,2,4,5-tetracyanobenzene (TMPD:TCNB) has been synthesized. The crystal structure of the black 1:1 complex formed between TMPD and TCNB has been determined by single crystal X-ray diffraction at room temperature. The compound crystallizes in the triclinic space group P-1 with cell dimensions: a = 7.4986(15) ?, b =7.6772(11) ?, c = 8.0764(15) ?, alpha = 78.822(12) degrees, beta = 83.3779(19) degrees, gamma = 86.289(17) degrees .TMPD and TCNB molecules are stacked alternately in infinite columns along the a-axis. The structure does not seem to show the usual pi-pi interaction between the two aromatic rings, but indicates an n-pi interaction localized between the nitrogen atoms of the donor and the cyano groups of the acceptor. 相似文献
22.
23.
Mifsud N Mellon V Perera KP Smith DW Echegoyen L 《The Journal of organic chemistry》2004,69(18):6124-6127
Electron paramagnetic resonance (EPR) spectroscopy was successfully used for the first time to follow the Bergman cyclization of bis-ortho-diynyl arene (BODA) compounds. Five BODA monomers with different spacer (X) and terminal groups (R) were compared. In situ polymerization via EPR spectroscopy yielded first-order rate expressions. Monomers with spacer -O- or -C(CF(3))(2) and terminal group R = Ph exhibited similar kinetic behavior upon thermal polymerization, whereas monomers with pyridine and thiophene terminal groups gave significantly higher rates of polymerization over phenyl-terminated derivatives. A model compound, 1,2-bis(phenylethynyl)benzene, was used to probe the polymerization mechanism, and radical intermediates were found to be stable indefinitely at room temperature. 相似文献
24.
Direct detection of ion pairs by fluorescence enhancement 总被引:1,自引:0,他引:1
Sensor 1 signals the simultaneous presence of sodium and phosphate with an increased fluorescence signal in the manner of a photoionic AND logic gate. 相似文献
25.
Anodic dissolution of copper in glycine solution at various hydrogen peroxide concentrations was investigated. The dissolution
rate increases, reaches a maximum, and then decreases with hydrogen peroxide concentration. Anodic polarization studies and
electrochemical impedance spectroscopy (EIS) studies were carried out to determine the mechanistic pathway of anodic dissolution
of copper in glycine system at three different hydrogen peroxide concentrations: one at low hydrogen peroxide concentration
in the active dissolution region, another in the maximum dissolution region, and the third at the high hydrogen peroxide concentration
in the post-peak-dissolution region. The EIS data in complex plane plots show presence of two capacitance loops and one negative
capacitance loop. The impedance plot patterns strongly depend on the hydrogen peroxide concentration in solution. Reaction
mechanism analysis technique was employed to model the EIS data. A three-step mechanism with two intermediate adsorbates and
a parallel dissolution by catalytic mechanism simulates EIS patterns which match the experimental trends. The intermediates
are likely to be cupric and cuprous oxides. The essential features of impedance spectra at various overpotentials at three
different hydrogen peroxide concentrations are captured by the proposed mechanism. The results also show that the film present
on the copper surface in glycine and hydrogen peroxide solutions does not passivate the surface. 相似文献
26.
We investigate the ratio of spin precession frequency to orbital frequency for a spinning charged particle confined to circular
orbit in the equatorial plane of a compact object, with a uniform magnetic field, as described by the Wald and the Ernst potentials.
In order to see the difference in behaviours for particles with differentg values we consider the cases of electron and proton separately. 相似文献
27.
28.
Nilmini K. Abayasinghe Sibylle Glaser K. Prasanna U. Perera Dennis W. Smith 《Journal of polymer science. Part A, Polymer chemistry》2005,43(21):5257-5266
Oligoethylene‐end‐capped polylactides were synthesized through the ring‐opening polymerization of L ‐lactide with alcohol‐terminated oligoethylenes as macroinitiators. The polymerization of L ‐lactide was carried out in bulk at 130 °C in the presence of stannous octoate and primary alcohols with four different molecular weights: 350, 425, 550, and 700 g/mol. The end‐capped copolymers that formed had a number‐average molecular weight of approximately 40,000 (weight‐average molecular weight/number‐average molecular weight = 1.7) according to gel permeation chromatography and were highly crystalline in comparison with the similarly formed homopolymer of L ‐lactide. The copolymer structure was characterized by Fourier transform infrared, NMR, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry, and differential scanning calorimetry analysis. This work focused on developing more crystallizable and hydrolytically stable polylactide derivatives that could potentially be used as compatibilizers in polylactide–polyolefin blends or as nucleating agents for poly(L ‐lactide) or other polyesters. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5257–5266, 2005 相似文献
29.
Prasanna S. Ghalsasi 《Polyhedron》2009,28(9-10):1856-1859
1,2,4,5-Tetracyanobenzene (TCNB), a moderate electron acceptor, reacts readily with N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD), a strong electron donor, to form black colored TMPD:TCNB complex when treated in 1:1 molar ratio. Single crystal X-ray diffraction studies on this complex showed that molecule of TMPD and TCNB are alternately stacked with an interplanar distance of 3.4 Å between them. The structure of the complex does not seem to show usual π–π interaction between the two aromatic rings, but indicates the presence of n–π interaction localized between the nitrogen atoms of TMPD and the cyano groups of TCNB. Along with this a prominent presence of CN···HAr hydrogen bonded ribbon network between nitrogen of cyanide moiety and hydrogen of neighboring aromatic carbon is observed with distance of 2.610 Å and angle of 147.19°. Magnetic measurements on the powdered compound using SQUID magnetometer (5–20 K) showed that the complex is weakly antiferromagnetic (θ = ?0.85 K). To my best knowledge CN···HAr interaction amongst electron acceptor molecules, to form a ribbon-like network, has not been observed before for a magnetic complex. 相似文献
30.
Large dendrimers, noted G(n)-3(n+2)cage, containing 3(n+2) o-carborane cluster cages MeC(2)B(10)H(10) at their peripheries (n = number of generation noted G(n)) have been synthesized by Huisgen-type azide alkyne Cu(I)-catalyzed dipolar "click" cycloaddition reactions (CuAAC) between an o-carborane monomeric cluster containing an ethynyl group and arene-centered azido-terminated dendrimers G(n)-3(n+2)N(3) of generations 0, 1, and 2. Attempts to synthesize higher-generation dendrimers of this family yielded insoluble materials. The carborane dendrimers G(0)-9cage, G(1)-27cage, and G(2)-81cage have been characterized by (1)H, (13)C, (11)B NMR, elemental analysis, matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectroscopy, and size exclusion chromatography (SEC) showing low polydispersities, dynamic light scattering (DLS) showing hydrodynamic diameters of 5.7 nm for the G(1)-27cage and the 12.9 nm for the G(2)-81cage. These dendrimers are extremely robust thermally, with 10% mass loss temperatures of 411 °C for the G(0)-9cage, 371 °C for the G(1)-27cage, and 392 °C for the G(2)-81cage. They all showed a strong absorption in the UV region peaking at 258 nm, whereas emission spectra of low intensities were observed between 280 and 480 nm. 相似文献