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11.
12.
The effect of vibrational structure on the frequency dependence of the first molecular hyperpolarizability of two thiophene-based charge-transfer chromophores is investigated. A time domain formulation is used to express the polarizability. The new expression includes the solvent-induced inhomogeneous distribution of electronic transition frequencies as well as the effect of the motion of solvent molecules that modulates the vibrational and electronic transition frequencies of the nonlinear optical molecule on which the first molecular hyperpolarizability depends. Resonance Raman scattering and one-photon absorption spectra of the chromophores are measured. By simultaneously fitting the experimental one-photon absorption spectrum and Raman cross sections of vibrational lines derived from resonance Raman scattering to a theoretical model, important parameters needed for the calculation of the first molecular hyperpolarizability are obtained. The first molecular hyperpolarizability is calculated as a function of frequency covering both nonresonance and two-photon resonance regions. The calculated result is compared with the measured hyperpolarizability as a function of frequency of the excitation laser. The resonance Raman-based analysis is shown to account reasonably well for the dispersion of the hyperpolarizability of the two charge transfer chromophores. 相似文献
13.
James L. Kelley James B. Thompson Virgil L. Styles Francis E. Soroko Barrett R. Cooper 《Journal of heterocyclic chemistry》1995,32(5):1423-1428
The 3H-imidazo[4,5-c]pyridazine, 1H-imidazo[4,5-d]pyridazine, and 1H-benzimidazole analogues of the potent anticonvulsant purine 9-(2-fluorobenzyl)-6-methylamino-9H-purine (1, 78U79) were synthesized and tested for anticonvulsant activity. The 3H-imidazo[4,5-c]pyridazines 8 and 9 were prepared in five stages from 3,4,5-trichloropyridazine (2) . The 1H-imidazolo[4,5-d]pyridazine 15 was synthesized in four stages from 5-[(benzyloxy)methyl]-1,5-dihydro-4H-imidazo[4,5-d] pyridazin-4-one (10a) . The benz-imidazole analogues 18 and 20 were prepared from 2,6-dinitroaniline in three stages. These compounds were one-tenth or less as active as 1 in protecting rats against maximal electroshock-induced seizures. 相似文献
14.
A method is described for the potentiometric titration of milligram quantities of the uranium(IV) ion in the presence of iron. This is accomplished by complexing the iron with 1.10-phcnanthroline. The uranium can then be titrated with standard ceric sulfate without interference from the iron. 相似文献
15.
Schmidt Sherry L. Myers Michele D. Kelley Stephen S. McMillan James D. Padukone Nandan 《Applied biochemistry and biotechnology》1997,(1):469-482
The use of membrane processes for the recovery of fermentation products has been gaining increased acceptance in recent years.
Pervaporation has been studied in the past as a process for simultaneous fermentation and recovery of volatile products such
as ethanol and butanol. However, membrane fouling and low permeate fluxes have imposed limitations on the effectiveness of
the process. In this study, we characterize the performance of a substituted polyacetylene membrane, poly[(l-trimethylsilyl)-l-propyne]
(PTMSP), in the recovery of ethanol from aqueous mixtures and fermentation broths. Pervaporation using PTMSP membranes shows
a distinct advantage over conventional poly(dimethyl siloxane) (PDMS) membranes in ethanol removal. The flux with PTMSP is
about threefold higher and the concentration factor is about twofold higher than the corresponding performance achieved with
PDMS under similar conditions. The performance of PTMSP with fermentation broths shows a reduction in both flux and concentration
factor relative to ethanol-water mixtures. However, the PTMSP membranes indicate initial promise of increased fouling resistance
in operation with cell-containing fermentation broths. 相似文献
16.
17.
G. Evan Boswell David L. Musso James L. Kelley Francis E. Soroko Barret R. Cooper 《Journal of heterocyclic chemistry》1996,33(1):33-39
A series of analogues of 2-phenylmorpholines with alkyl substituents at the C-3 position were synthesized for anti-tetrabenazine (anti-TBZ) testing in mice. The target compounds were prepared by reaction of (2-bromoalkyl) phenyl ketones 21a-h with the appropriate aminoalcohol 20a-b to form morpholinols 22a-h . Hydride reduction of the morpholinols gave aminodiols 23a-h which were cyclized to morpholines 6, 8, 10–12, 14–16, 18 and 19 by acid catalaysis. Compounds 7, 9, 13 and 17 were prepared by reductive formylation. The smaller straight chain substituents of 6, 8, 12 and 15 , and the beta branching of the iso-butyl group of 16 were well tolerated; anti-tetrabenazine ED50′s were comparable to compounds 2–5 . The α-branched, N-methylated, and side chain aryl derivatives were less active. 相似文献
18.
19.
Selective Exo‐Enzymatic Labeling of N‐Glycans on the Surface of Living Cells by Recombinant ST6Gal I
20.
Dr. Michael L. Tarlton Dr. Xiaojuan Yu Robert J. Ward Dr. Steven P. Kelley Dr. Jochen Autschbach Dr. Justin R. Walensky 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(58):14396-14400
The coordination of tBuNC and CO with the diarsenido complexes (C5Me5)2An(η2-As2Mes2), An=Th, U, has been investigated. For the first time, a comparison between isostructural complexes of ThIV and UIV has been possible with CO; density functional calculations indicated an appreciable amount of π backbonding that originates from charge transfer from an actinide-arsenic sigma bond. The calculated CO stretching frequencies in the ThIV and UIV diarsenido complexes are consistent with the experimental measurements, both show large shifts to lower frequency. We demonstrate that the π backbonding is crucial to explaining the red shifts of CO frequency upon AnIV complex formation. Interestingly, this interaction essentially correlates to the parallel orientation of π*(C−O) orbitals relative to the An−As bond. 相似文献