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21.
Alexei Yu. Lukin Sergei V. Shevyakov Alexei V. Laptev Olga I. Davydova Vitali I. Shvets Olga V. Demina Yury P. Strokach Valery A. Barachevsky Michail V. Alfimov Sergei P. Gromov Artem I. Vedernikov Johan Lugtenburg Andrey A. Khodonov 《Journal of inclusion phenomena and macrocyclic chemistry》2004,49(1-2):153-161
An effective synthetic approach to the preparation of a new crown-ether vinylogs involving the Horner–Emmons olefination of carbonyl precursors with the use of C2- and C5-phosphonates was proposed. The effects of the conjugation chain length and the nature of the terminal polar functions in the phosphonate reagent on the yield and process stereoselectivity were discussed. 相似文献
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Lensovet Leningrad Technological Institute. Plastpolimer Okhta Scientific-Production Association. Translated from Zhurnal Strukturnoi Khimii, Vol. 32, No. 4, pp. 22–28, July–August, 1991. 相似文献
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NMR spectroscopic studies reveal that binding of Na(+) by tris(2-methoxyphenyl)amine (3) brings two of these tripod ethers together about the metal ion; the related double-tripod-ether ionophore 1,2-bis[2-(bis(2-methoxyphenyl)amino)phenoxy]ethane (4), in which two triarylamines are covalently attached, binds LiI, LiBPh(4), NaI, NaBPh(4), and KB(4-ClPh)(4). Dynamic NMR puts lower limits on binding free energies of 4 for Na(+) (71.8 kJ mol(-)(1)) and K(+) (66.8 kJ mol(-)(1)) ions. X-ray studies of 3(2).NaBPh(4), 4.NaBPh(4), 4.NaB(4-ClPh)(4), and 4.KB(4-ClPh)(4).CH(3)NO(2) show eight-coordinate M(+) ions bound between crystallographically independent, homochiral triarylamine tripod ethers in structures reminiscent of alkali metal [2.2.2] cryptates. Complexes crystallize as follows: 3(2).NaBPh(4), monoclinic, P2(1)/c, Z = 4, a = 10.701(3) ?, b = 37.593(3) ?, c = 13.774(2) ?, and beta = 98.24(2) degrees; 4.NaBPh(4), triclinic, P&onemacr;, Z = 2, a = 12.157(1) ?, b = 14.811(1) ?, c = 15.860(2) ?, alpha = 105.400(8) degrees, beta = 91.594(9) degrees, and gamma = 95.354(8) degrees; 4.NaB(4-ClPh)(4), monoclinic, P2(1)/n, Z = 4, a = 13.652(5) ?, b = 18.75(1) ?, c = 22.805(5) ?, and beta = 92.21(5) degrees; 4.KB(4-ClPh)(4).CH(3)NO(2), monoclinic, Pn, Z = 2, a = 13.663(4) ?, b = 12.228(3) ?, c = 18.712(8) ?, and beta = 91.45(3) degrees. They show variable N-M-N angles; 3(2).NaBPh(4) is surprisingly bent ( angleN-Na-N = 154.5 degrees ), while the 4.M(+) complexes are normal: nearly linear for Na(+) ( angleN-Na-N = 178.6, 178.1 degrees ) and again bent with the larger K(+) ( angleN-K-N = 164.5 degrees ). Finally, free 4 is structurally similar to 3; it crystallizes in the triclinic space group P&onemacr;, with Z = 2, a = 8.068(1) ?, b = 14.599(2) ?, c = 16.475(3) ?, alpha = 115.43(1) degrees, beta = 92.51(1) degrees, and gamma = 90.40(1) degrees. 相似文献
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Merchant KA Noid WG Akiyama R Finkelstein IJ Goun A McClain BL Loring RF Fayer MD 《Journal of the American Chemical Society》2003,125(45):13804-13818
Spectrally resolved infrared stimulated vibrational echo data were obtained for sperm whale carbonmonoxymyoglobin (MbCO) at 300 K. The measured dephasing dynamics of the CO ligand are in agreement with dephasing dynamics calculated with molecular dynamics (MD) simulations for MbCO with the residue histidine-64 (His64) having its imidazole epsilon nitrogen protonated (N(epsilon)-H). The two conformational substate structures B(epsilon) and R(epsilon) observed in the MD simulations are assigned to the spectroscopic A(1) and A(3) conformational substates of MbCO, respectively, based on the agreement between the experimentally measured and calculated dephasing dynamics for these substates. In the A(1) substate, the N(epsilon)-H proton and N(delta) of His64 are approximately equidistant from the CO ligand, while in the A(3) substate, the N(epsilon)-H of His64 is oriented toward the CO, and the N(delta) is on the surface of the protein. The MD simulations show that dynamics of His64 represent the major source of vibrational dephasing of the CO ligand in the A(3) state on both femtosecond and picosecond time scales. Dephasing in the A(1) state is controlled by His64 on femtosecond time scales, and by the rest of the protein and the water solvent on longer time scales. 相似文献
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V. S. Bogdanov S. V. Baranin A. Dib I. P. Yakovlev V. A. Dorokhov 《Russian Chemical Bulletin》1992,41(9):1693-1699
Mono- and binuclear boron chelates have been synthesized by the action of butylthiodibutylborane on the ethyl esters of 4-[N-(R-pyrid-2-yl)carbamoyl]-3-amino-2-cyanobuten-2-ic acids (codimers of N-(R-pyrid-2-yl) amides and the ethyl ester of cyanoacetic acid). Complexes of this type can exist in solution in the form of two tautomers: acetamide acid derivatives or the corresponding ketene N,O-acetals.N. D. Zelinski Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 9, pp. 2162–2170, September, 1992. 相似文献
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Quantitative theory of orientational behavior of rodlike polyelectrolytes in dilute solution is developed. We find that in salt-free solutions many-body Coulomb interactions between macro- and counterions favor nematic ordering. It is shown that the orientationally isotropic phase of the solution becomes unstable toward nematic ordering at polymer concentration smaller than the overlap concentration. Our predictions are consistent with experimental observations for synthetic polyelectrolytes poly(p-phenylene)sulfonates in aqueous solutions. 相似文献
30.
Apparent two-dimensional behavior of TiO2 nanotubes revealed by light absorption and luminescence 总被引:1,自引:0,他引:1
Bavykin DV Gordeev SN Moskalenko AV Lapkin AA Walsh FC 《The journal of physical chemistry. B》2005,109(18):8565-8569
Optical absorption and photoluminescence (PL) properties of colloidal TiO(2) nanotubes, produced by the alkali hydrothermal method, were studied at room temperature in the range 300-700 nm. Nanotubes having an internal diameter in the range 2.5-5 nm have very similar optical properties, in contrast to the expected behavior for quasi-1-D systems. This is explained by the complete thermal smearing of all 1-D effects, due to the large effective mass of charge carriers in TiO(2), resulting in an apparent 2-D behavior of TiO(2) nanotubes. 相似文献