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21.
V. V. Ermolenko S. G. Kruglik S. N. Terekhov P.-Y. Turpin V. A. Orlovich 《Journal of Applied Spectroscopy》2004,71(1):27-34
By the resonance Raman scattering spectroscopy (RRS) method, photoinduced processes involving cationic Ni-5,10,15,20-tetrakis(4-N-methylapyridiniumyl)porphyrin (Ni(TMpy-P4)) in a phosphate water buffer have been investigated. Excitation into different regions of the Soret band at wavelengths of 397, 423, 441.6, and 457.9 nm permitted separate investigation of the behavior of the 4- and 6-coordinated forms of Ni(TMpy-P4). It has been found that Ni(TMpy-P4) is characterized by two photoinduced processes: the deactivation of initially 4-coordinated Ni(TMpy-P4) is followed by the addition to it, as axial ligands, of two water molecules from the environment to form a nonequilibrium 6-coordinated form Ni(TMpy-P4)(H2O)2 in the ground state, whereas in the process of deactivation of the excited 6-coordinated complex there occurs a dissociation of the axial water ligands to form a nonequilibrium 4-coordinated complex Ni(TMpy-P4) in the ground state. Some of the 4-coordinated molecules of Ni(TMpy-P4) are deactivated through the excited B
1g
*-state without undergoing extracoordination. Quantitative analysis of the RRS spectra using the global fitting method has shown that in the course of deactivation 33% of photoexcited 6-coordinated molecules of Ni(TMpy-P4)(H2O)2 retain their axial ligands, relaxing through the dark long-lived intermediate state of the 6-coordinated form. 相似文献
22.
S.?N.?TerekhovEmail author V.?S.?Chirvony P.-Y.?Turpin 《Journal of Applied Spectroscopy》2005,72(4):585-593
Using the methods of absorption spectroscopy and resonance Raman scattering, we have made a comparative study of water-soluble
cationic Co(II)- and Co(III)-5,10,15,20-tetrakis(4-N-methyl-pyridiniumyl)porphyrins(CoII(TMpy-P4) and CoIII(TMpy-P4) with DNA and synthetic single- and double-stranded polynucleotides. It has been found that CoII(TMpy-P4), which in aqueous solutions containing no nucleic acids is readily oxidized to CoIII(TMpy-P4) by the molecular oxygen dissolved there, markedly changes its oxidation ability when bound to nucleic acid. Under
interaction with guanine-containing polynucleotides, the rate of change in the oxidation state of cobalt from Co(II) to Co(III)
increases as compared to such for the solution of porphyrin in a buffer. But in complexes with DNA and adenine- and thymine-containing
polynucleotides, CoII(TMpy-P4), on the contrary, becomes stable. The observed effects of inhibition/promotion of CoII(TMpy-P4) oxidation when it is bound to nucleic acids are assumed to be due to the weakening/strengthening of the electron-donor
properties of the extraligand on cobalt, which leads to a change in cobalt affinity to molecular oxygen. The role of immobilized
water molecules in the change in the properties of cobalt extraligands has been considered. On the basis of the analysis of
the spectral data obtained, modes for incorporating CoII(TMpy-P4) into DNA and model polynucleotides are proposed.
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Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 4, pp. 538–545, July–August 2005. 相似文献
23.
The reactivity of homobimetallic complexes of platinum(II) and palladium(II) containing diethyl(diphenylphosphinomethyl)amine (ddpa = (C6H5)2PCH2N(C2H5)2) as a bridging ligand has been investigated. Carbon monoxide reacts reversibly with these complexes. The species formed are binuclear carbonyl-bridged derivatives, which can isomerize to ionic terminal carbonyl complexes. Reaction of [PtCl2(CO)]2[(C2H5)4N]2 with ddpa in dichloromethane gives the ionic platinum(I) complex [Pt(ddpa)Cl2]2[(C2H5)4N]2, which reacts with carbon monoxide. Still, homobimetallic derivatives of palladium(I) are unstable, and none have been isolated. 相似文献
24.
Kim DJ Dunn BC Cole P Turpin G Ernst RD Pugmire RJ Kang M Kim JM Eyring EM 《Chemical communications (Cambridge, England)》2005,(11):1462-1464
The silylation of SBA-15 enhances the reducibility of cobalt oxides on a SBA-15 supported cobalt catalyst, and consequently increases the catalytic activity for Fischer-Tropsch synthesis of hydrocarbons from syngas and selectivity for longer chain products. 相似文献
25.
P. Y. Turpin L. Chinsky A. Laigle M. Tsuboi J. R. Kincaid K. Nakamoto 《Photochemistry and photobiology》1990,51(5):519-525
The resonance Raman spectra of water-soluble porphyrins, Cu(TMpy-P4) and Ni(TMpy-P4), and their mixtures with DNA, Poly(dG-dC).Poly(dG-dC), and Poly(dA-dT).Poly(dA-dT) were measured using 426 nm pulsed laser excitation (and 556 nm for some applications). At high laser power, the solution of Cu(TMpy-P4) mixed with DNA or Poly(dA-dT).Poly(dA-dT) exhibits new bands at 1550 and 1349 cm-1 that are not observed for Cu(TMpy-P4) alone or for Cu(TMpy-P4) mixed with Poly(dG-dC).Poly(dG-dC). These extra bands do not appear when the resonance Raman spectra are measured by a cw laser or by a pulsed laser with low power. Similar mixtures of M(TMpy-P4) (where M = Ni, Zn, Co, Mn, and H2) with these nucleic acids exhibit no such bands even by high power pulsed laser excitation. We attribute the new resonance Raman bands to an electronically excited Cu(TMpy-P4), stabilized by forming an exciplex with the A-T site of the nucleic acid. The minimum lifetime value of such an exciplex was estimated to be on the order of 10 ps. 相似文献
26.
B. P. Ablitt K. I. Hopcraft K. D. Turpin P. C. Y. Chang J. G. Walker E. Jakeman 《Waves in Random and Complex Media》1999,9(4):561-572
This paper examines the behaviour of polarized light scattered by a medium containing small chiral spheroidal particles. We show that for single scattering the observed phenomena of optical activity may be interpreted in terms of an averaged Mueller matrix and describe how the degree of polarization is affected by such a medium. The polarization properties of multiply scattered light by chiral particles are considered through the use of Monte Carlo simulations. It is shown that the effects of chirality under multiple scattering can be interpreted as an order-preserving influence in a disordered system and that this influence can, in principle, be exploited for the purposes of imaging. 相似文献
27.
Jennifer L. Gasser-Ramirez Brian C. Dunn Daniel W. Ramirez Eric P. Fillerup Gregory C. Turpin Yifan Shi Richard D. Ernst Ronald J. Pugmire Edward M. Eyring Katherine A. Pettigrew Debra R. Rolison Joel M. Harris 《Journal of Non》2008,354(52-54):5509-5514
A simple synthetic route for preparing high surface area, structurally stable ceria aerogels is presented. Ceria aerogels were doped with 1% palladium: a water-gas shift (WGS) active metal. A reduced Pd/ceria aerogel and an as-prepared Pd/ceria aerogel are compared to determine the effect of pretreatment conditions on WGS activity. The BET surface area of the as-prepared ceria aerogel was 345 m2/g. CO chemisorption data and high-resolution TEM images indicate that the particle size of palladium on the reduced Pd/ceria sample was approximately 15 nm. X-ray photoelectron spectroscopy (XPS) data establish that the fraction of Ce3+ from Ce2O3 was approximately the same for both reduced and as-prepared samples. XPS data also indicate that approximately 44% of the palladium on the reduced Pd/ceria sample was converted to the metallic form. Each catalyst was tested for WGS activity. The reduced Pd/ceria sample exhibited the greatest WGS activity as compared with the other samples used in this study. 相似文献
28.
Victor Turpin Dr. Mehdi A. Beniddir Dr. Grégory Genta-Jouve Dr. Adam Skiredj Jean-François Gallard Karine Leblanc Dr. Pierre Le Pogam Prof. Dr. Erwan Poupon 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(57):12936-12940
Camellimidazoles A–C were recently reported as natural substances in Keemun black tea. Although a “biosynthetic” route to these intriguing imidazole dimers was proposed from caffeine by the authors in this seminal report, we envisioned that a artefactual scenario, consisting of alkaline hydrolysis of caffeine and spontaneous cascade reactions with a methylene donor such as formaldehyde or methylene chloride, could also have led to their formation. To capture the diversity of molecules obtained under these conditions (i.e. alkaline treatment of caffeine/formaldehyde), an in silico MetWork-based pipeline was implemented, highlighting the sought-after camellimidazoles B and C. A wealth of further compounds were also tagged, notably comprising the herein newly described and unnatural camellimidazoles D –F that were subsequently confirmed as anticipated in silico upon extensive spectroscopic analyses. Likewise, camellimidazoles B and C could also be obtained using methylene chloride as an alternative methylene donor which may also have occurred in the initial phytochemical pipeline that implied this solvent. The current investigation emphasizes the fitness of MetWork tagging to extend the logic of in silico anticipation of metabolic pathways to organic chemistry reactions. 相似文献
29.
Robert Deschenaux Florence Monnet Elisabeth Serrano Franois Turpin Anne-Marie Levelut 《Helvetica chimica acta》1998,81(11):2072-2077
The synthesis and liquid-crystalline properties of tetracatenar covalent and H-bonded bis-ferrocene derivatives 1 and 2 , respectively, are reported. Both compounds gave rise to enantiotropic columnar liquid-crystalline behavior with a hexagonal molecular organization. To explore the possibility to obtain also calamitic liquid-crystalline phases from H-bonded ferrocene-containing liquid crystals, a rod-shaped ferrocene mesogen 3 was synthesized, which gave rise to enantiotropic smectic C and smectic A phases. For the first time, a rational synthetic design at the ferrocene level led to ferrocene-based liquid-crystals with columnar behavior and to H-bonded metallomesogens. 相似文献
30.
V. A. Galievskii V. S. Chirvonyi S. G. Kruglik P. A. Apanasevich V. V. Ermolenkov V. A. Orlovich L. Chinsky P. -Y. Turpin 《Journal of Applied Spectroscopy》1995,62(2):275-284
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 62, No. 2, pp. 110–121, March–April, 1995. 相似文献