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41.
Herein, we report the study of the three-photon absorption cross-section dependence on solvents parameters for a highly conjugated organic dye, 2,2'-(4,4'-(1E,1'E)-2,2'-(9,9-didecyl-9H-fluorene-2,7-diyl) bis(ethene-2,1-diyl)bis(4,1-phenylene))dibenzo[d]thiazole (A-pi-pi-pi-A). The three-photon absorption cross-section was measured for this organic dye in solution in four different solvents with polarity function, Deltaf between 0.162 and 0.247. The experiments show how the solvent's reorientation of the electrons and polarity contribute to the 3PA cross-section. Multiphoton-absorption experiments of A-pi-pi-pi-A in all four different solvents were performed with a tunable OPG pumped by a 25 picosecond Nd-YAG laser. 相似文献
42.
Cohanoschi I Belfield KD Toro C Yao S Hernández FE 《The Journal of chemical physics》2006,124(19):194707
The three-photon absorption cross sections of three different fluorene derivatives, with extended pi-electron conjugation lengths was experimentally measured and compared with shorter pi-electron conjugation length analogs. The effect of the conjugation length on the three-photon absorption cross section sigma(3) (') of this family of molecules has been elucidated. It is demonstrated that sigma(3) (') of the asymmetric compound D-pi-pi-pi-A is 6.6 times larger than its shorter configuration D-pi-A, while for the symmetric compounds D-pi-pi-pi-D and A-pi-pi-pi-A a two-fold enhancement was found relative to their shorter conjugation length analogs. Measurements of the three-photon excitation of these compounds in THF solution (10(-3)M) were accomplished with a tunable optical pulse generation pumped by a 25 ps Nd-YAG laser. 相似文献
43.
Arce VB Della Védova CO Downs AJ Parsons S Romano RM 《The Journal of organic chemistry》2006,71(9):3423-3428
The conformational properties of gaseous trichloromethyl chloroformate (or "diphosgene"), ClC(O)OCCl3, have been studied by vibrational spectroscopy [IR (gas), IR (matrix), and Raman (liquid)] and quantum chemical calculations (MP2 and B3LYP with 6-311G basis sets); in addition, the structure of a single crystal at low temperature has been determined by X-ray diffraction. ClC(O)OCCl3 exhibits only one conformational form having Cs symmetry with a synperiplanar orientation of the C-O single bond relative to the C=O double bond. The calculated energy difference between the syn and anti forms, 5.73 kcal mol(-1) (B3LYP) or 7.06 kcal mol(-1) (MP2), is consistent with the experimental findings for the gas and liquid phases. The crystalline solid at 150 K [monoclinic, P2(1)/n, a = 5.5578(5) angstroms, b = 14.2895(12) angstroms, c = 8.6246(7) angstroms, beta = 102.443(2) degrees, Z = 4] likewise consists only of molecules in the syn form. 相似文献
44.
A new hexane-in-water microemulsion was investigated as buffer in microemulsion EKC (MEEKC). At difference with other microemulsions, the addition of cosurfactant was not necessary to stabilize the microemulsion. The proposed microemulsion was successfully used to achieve electrophoretic separation of seven antibiotics including nitroimidazoles, cephapirin and tetracyclines. Selectivity and separation efficiency achieved in MEEKC were compared with MEKC. MEEKC technique proved to be more efficient than MEKC for performing the separation of the analytes and the presence of microemulsions was found to be critical to achieve the separation of tetracyclines. The proposed microemulsion also points out that solvents with high volatility, such as hexane, can be stabilized and used as a microemulsion of SDS. 相似文献
45.
46.
A. Castiñeiras Gladys Diaz F. Florencio S. Garcia-Blanco S. Martinez-Carrera 《Journal of chemical crystallography》1988,18(4):395-401
Summary The X-ray crystal structure of the title compound, [Hg2(C16H20N2S2)I4], has been determined. The crystals are monoclinic (space groupP21/c), with cell dimensionsa=15.016(2),b=6.201(3),c=15.273(2) Å,=115.18(1)°;V
o
=1287.0(7) Å3,M
r
=1213.266,Z=4,D
x
=6.26mg m–3, MoK radiation (graphite crystal monochromator,
),(MoK)=336 cm–1,F(000)=4272, andT=290°K. The final conventionalR factor=0.054, andR
w
=0.062 for 2799 observed reflections. The structure was solved by Patterson and Fourier methods and refined by block-diagonal least-squares methods. The coordination around the mercury atoms is approximately tetrahedral, although with considerable distortion, with two iodine atoms and the N and S atoms of one-half of the ligand molecule. 相似文献
47.
José Ricardo Cammarata Rocío Rivera Franmerly Fuentes Yomaira Otero Edgar Ocando-Mavárez Alejandro Arce Juan M. Garcia 《Tetrahedron letters》2017,58(43):4078-4081
An air stable copper(I)-phosphole complex, [CuCl{2,5-bis(2-thienyl)-1-phenylphosphole}2] (1), was utilized as a catalyst in single and double A3-coupling reactions for preparing mono- and bi-propargylamines. A variety of aldehydes, amines and terminal alkynes were tested. Most of these reactions led to formation of the expected propargylamines in good yields using low amounts catalyst and obviating both the use of purified reagents as employ of a glovebox. 相似文献
48.
49.
We studied the kinetics of the chlorination of amines by sodium hypochlorite in strongly alkaline aqueous solution. A reaction mechanism compatible with experimental results is proposed and discussed. © 1995 John Wiley & Sons, Inc. 相似文献
50.
We consider the Tikhonov regularizer fλ of a smooth function f ε H2m[0, 1], defined as the solution (see [1]) to We prove that if f(j)(0) = f(j)(1) = 0, J = m, …, k < 2m − 1, then ¦f − fλ¦j2 Rλ(2k − 2j + 3)/2m, J = 0, …, m. A detailed analysis is given of the effect of the boundary on convergence rates. 相似文献