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91.
A range of neutral metal-organometallic coordination networks (MOMNs) containing both backbone and pendant metal sites have been synthesized and characterized. These materials consist of metal ions or metal ion clusters as nodes that are linked by the bifunctional “organometalloligand” (η4-benzoquinone)Mn(CO)3−, which binds through the quinone oxygen atoms. The resulting MOMNs can be rationally designed to a significant extent based upon a knowledge of the electronic and geometrical requirements of the metal ion nodes, the solvent, organometalloligand substituents, and the presence or absence of organic spacers. An impressive range of architectures have been accessed in this manner, suggesting that the use of π-organometallics in coordination directed self-assembly holds much promise. 相似文献
92.
Maria Bykhovskaia Boris Gelmont Tatiana Globus Dwight L. Woolard Alan C. Samuels Tap Ha Duong Krystyna Zakrzewska 《Theoretical chemistry accounts》2001,106(1-2):22-27
We present a computational method which couples normal mode analysis in internal coordinates of a molecule with very far
IR spectroscopy. The analytical expression for the dependence of IR absorption on frequency incorporates frequencies and optical
activities of each normal mode. In order to predict far-IR spectra of a molecule we evaluate the optical activity of each
normal mode. This optical activity is determined by the vibration amplitude of the dipole moment produced by a normal mode.
We calculated normal modes of DNA double-helical fragments (dA)12 · (dT)12 and (dA-dT)6 · (dA-dT)6 and evaluated their optical activities. These were found to be very sensitive to the DNA base-pair sequence. The positions
of the resonance peaks in the calculated absorption spectrum of (dA)12 · (dT)12 are in a good agreement with those obtained by Fourier transform IR spectroscopy (Powell JW et al. 1987 Phys Rev A 35: 3929–3939).
Received: 20 June 2000 / Accepted: 5 January 2001/ Published online: 3 May 2001 相似文献
93.
Lisa M. Kozycz Dong Gao Andrew J. Tilley Dwight S. Seferos 《Journal of polymer science. Part A, Polymer chemistry》2014,52(23):3337-3345
A series of one donor–two acceptor (D–A1)‐(D–A2) random terpolymers containing a 2,7‐carbazole donor and varying compositions of perylene diimide (PDI) and naphthalene diimide (NDI) acceptors was synthesized via Suzuki coupling polymerization. The optical properties of the terpolymers are weighted sums of the constituent parent copolymers and all show strong absorption over the 400 to 700 nm range with optical bandgaps ranging from 1.77 to 1.87 eV, depending on acceptor composition. The copolymers were tested as acceptor materials in bulk heterojunction all‐polymer solar cells using poly[(4,8‐bis‐(2‐ethylhexyloxy)‐benzo[1,2‐b;4,5‐b′]dithiophene)‐2,6‐diyl‐alt‐(4‐(2‐ethylhexanoyl)‐thieno[3,4‐b]thiophene)‐2,6‐diyl] (PBDTTT‐C) as the donor material. In contrast to the optoelectronic properties, the measured device parameters are not composition dependent, and rather depend solely on the presence of the NDI unit, where the devices containing any amount of NDI perform half as well as those using the parent polymer containing only carbazole and PDI. Overall this is the first example of a one donor–two acceptor random terpolymer system containing perylene diimide (PDI) and naphthalene diimide (NDI) acceptor units, and demonstrates a facile method of tuning polymer optoelectronic properties while minimizing the need for complicated synthetic and purification steps. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3337–3345 相似文献
94.
2,3-Dihydrobenzofuran-3-spiro-4′-dihydropyridines are readily available via intramolecular addition of enolates to pyridinium ions. 相似文献
95.
96.
Here it is proved that a cyclic (n, k) code over GF(q) is equidistant if and only if its parity check polynomial is irreducible and has exponent where a divides q ? 1 and (a, k) = 1. The length n may be any multiple of e. The proof of this theorem also shows that if a cyclic (n,k) code over GF(q) is not a repetition of a shorter code and the average weight of its nonzero code words is integral, then its parity check polynomial is irreducible over GF(q) with exponent where a divides q ? 1. 相似文献
97.
James A. Larame Brian Arbogast Eugene P. Stirchak Dwight D. Weller Max L. Deinzer 《Journal of mass spectrometry : JMS》1990,25(4):219-224
Carbamate-linked Oligodeoxynucleosides, in which the backbone consists of carbamate and N-methylcarbamate linkages, have been analyzed by negative ion liquid secondary ion mass spectrometry. Bidirectional sequence-determining fragmentations are postulated to occur from a common radical anion intermediate that is produced by capture of an ionizing electron by the neutral sample molecule. Fragmentation reactions appear to be related to whether a proton or methyl group is present on the amide nitrogen. 相似文献
98.
A simple system of five nonlinear ordinary differential equations is shown to reproduce many dynamical features of spiral waves in two-dimensional excitable media. 相似文献
99.
P. Merchant R. Collins R. Kershaw K. Dwight A. Wold 《Journal of solid state chemistry》1979,27(3):307-315
A study has been made of the electrical, optical and photoconducting properties of pure and reduced single crystals of composition Fe2?xCrxO3 where 0 ? x ? 0.47. It has been found that pure α-Fe2O3 is not a photoconductor. When defect-free crystals of α-Fe2O3 are reduced a surface layer of Fe3O4 is formed and the crystals exhibit photoconductivity. Removal of this layer resulted in the disappearance of photocurrents and an increase in the sample resistivity. A necessary condition for the observation of photocurrents in n-type Fe2O3 is that some Fe3O4 be present. In addition, it has been found that the substitution of chromium for iron in α-Fe2O3 results in a monotonically decreasing optical band gap as the chromium concentration, x, increases. 相似文献
100.
J. Baglio E. Kamieniecki N. DeCola C. Struck J. Marzik K. Dwight A. Wold 《Journal of solid state chemistry》1983,49(2):166-179
Single crystals of n- and p-WS2 were obtained by chemical vapor transport using chlorine and bromine as transporting agents. The best niobium-doped WS2 crystals were obtained when the concentration of the charge (formulated (1 ? x)WS2 · (x)NbS2) was ? 37 mg charge/ml of tube, and x = 0.01 to 0.03. A thermodynamic analysis of the crystal growth process is consistent with the observed doping concentration and other properties of the crystals obtained by this process. The crystals grown are characterized by electrical transport and surface photovoltage measured capacitance techniques. 相似文献