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排序方式: 共有295条查询结果,搜索用时 31 毫秒
51.
D. Khattib M. Ishan Dr. S. Karmakar Dr. H. Kostrhunova Prof. V. Brabec Prof. D. Gibson 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(43):9475-9480
The oxidation of cis-[Pt(NH3)2(OAc)2] with H2O2 yields a mixture of two isomers: ctc-[Pt(NH3)2(OH)2(OAc)2] and ctc-[Pt(NH3)2(OH)(OAc)(OH)(OAc)]. Following modification with 4-phenylbutyric (PhB) anhydride, two isomers were separated and characterized; the symmetric ctc-[Pt(NH3)2(PhB)2(OAc)2] ( 1 ) and the nonsymmetric ctc-[Pt(NH3)2(PhB)(OAc)(PhB)(OAc)] ( 2 ). They differ in their log P values and despite having similar cellular uptake and similar DNA platination levels, the symmetric ctc-[Pt(NH3)2(OH)2(OAc)2] is more than 4-fold more potent than the nonsymmetric isomer in a panel of 4 cancer cell lines. 相似文献
52.
Manas Chakrabarty Ratna Mukherjee Sulakshana Karmakar Yoshihiro Harigaya 《Monatshefte für Chemie / Chemical Monthly》2007,138(12):1279-1282
Summary. 2-Substituted and 1,2-disubstited benzimidazoles were prepared efficiently from o-phenylenediamines and aryl aldehydes using p-toluenesulphonic acid (5 mol%)-on-silica gel as a cheap and environmentally benign catalyst. 相似文献
53.
Numerical modelling of a direct current non-transferred thermal plasma torch for optimal performance
A laminar steady-state 2D axisymmetric model of a direct current (DC) thermal plasma torch using a magneto-hydrodynamic approach has been developed. The model takes into account the entire torch system comprising the plasma gas injection, the inner region of the torch, and the jet exiting into the ambient environment. Numerical results are obtained for two different power inputs chosen from published experimental data. The temperature predictions at the torch exit are found in good agreement with experimental results. Velocity analysis of the plasma jet has been presented and the impact of electromagnetic force on jet velocity is analysed. The Lorentz force arising due to the coupling of fluid motion and electromagnetic forces shoots up the jet velocity to significantly high values near the cathode tip. Temperature and velocity profiles are in good agreement with the characteristics of a long laminar plasma jet. An operating value of heat transfer coefficient (h) has been suggested for optimal torch operation, thus ensuring a low anode erosion rate and acceptable thermal efficiency. The argon torch has the maximum temperature and longest jet length among the plasma gases considered. 相似文献
54.
Parnajyoti Karmakar Subhasis Mallick Biplab K. Bera Arup Mandal Subala Mondal Sudip K. Mukhopadhyay Alak K. Ghosh 《Transition Metal Chemistry》2010,35(8):911-916
The kinetics of the interaction of glycine-l-leucine (Glyleu) with cis-[Pt(cis-dach)(OH2)2]2+ (dach = 1,2-diaminocyclohexane) has been studied spectrophotometrically as a function of [cis-[Pt(cis-dach)(OH2)2]2+], [Glyleu] and temperature at pH 4.0, where the complex exists predominantly as the diaqua species and Glyleu as a zwitterion.
The substitution reaction shows two consecutive steps: the first is the ligand-assisted anation and the second is the chelation
step. The activation parameters for both the steps were evaluated using Eyring’s equation. The low ∆H1≠ (51.9 ± 2.8 kJmol−1) and large negative value of ∆S1≠ (−152 ± 8 JK−1mol−1) as well as ∆H2≠ (54.4 ± 1.7 kJmol−1) and ∆S2≠ (−162 ± 5 JK−1mol−1) indicate an associative mode of activation for both the aqua ligand substitution processes. 相似文献
55.
Biplab K. Bera Subhasis Mallick Arup Mandal Parnajyoti Karmakar Asok K. Datta Alak K. Ghosh 《Transition Metal Chemistry》2010,35(5):541-547
The kinetics of the aqua ligand substitution from hydroxopentaaquarhodium(III) ion, [Rh(H2O)5(OH)]2+, by l-Arginine has been studied spectrophotometrically as a function of Arginine concentration, and temperature, at pH 4.3. The
reaction proceeds via a rapid outer sphere association complex formation step followed by two consecutive steps. The first
of these involves ligand-assisted anation, while the second involves chelation as the second aqua ligand is displaced. The
association equilibrium constant for the outer sphere complex formation has been evaluated together with the rate constants
for the two subsequent steps. The activation parameters for both steps have been evaluated using Eyring’s equation. Thermodynamic
parameters calculated from the temperature dependence of the outer sphere association equilibrium constants are also consistent
with an associative mode of activation. The product of the reaction has been characterized by conductivity measurement and
IR spectroscopic analysis. 相似文献
56.
Tandra?Das Biplab?K.?Bera Subhasis?Mallick Parnajyoti?Karmakar Arup?Mandal Subala?Mondal Gauri?S.?De Alak?K.?Ghosh 《Transition Metal Chemistry》2010,35(7):885-890
The interaction of thiosemicarbazide with the title complex has been studied spectrophotometrically in aqueous medium as a
function of [complex], [thiosemicarbazide], pH and temperature at constant ionic strength. At pH 7.4, the reaction shows two
distinct paths; both of which are [thiosemicarbazide] dependent. A parallel reaction scheme fits well with the experimental
findings. An associative interchange mechanism is proposed for both the paths; the activation parameters calculated from Eyring
plots are ΔH1≠ = 14.2 ± 0.8 kJ mol−1, ΔS1≠ = −241 ± 2 JK−1 mol−1, ΔH2≠ = 30.8 ± 1.4 kJ mol−1 and ΔS2≠ = −236 ± 4 JK−1 mol−1. From the temperature dependence of the outer sphere association complex equilibrium constants, the thermodynamic parameters
calculated are ΔH1° = 34.25 ± 1.9 kJ mol−1, ΔS1° = 146 ± 6 J K−1 mol−1 and ΔH2° = 9.4 ± 1.1 kJ mol−1, ΔS2° = 71 ± 3 JK−1 mol−1, which gives a negative ΔG° at all temperatures studied, supporting the spontaneous formation of an outer sphere association
complex. 相似文献
57.
Mantosh K. Sinha Ofer Reany Dr. Galit Parvari Ananta Karmakar Dr. Ehud Keinan Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(30):9056-9067
4‐Aminobipyridine derivatives form strong inclusion complexes with cucurbit[6]uril, exhibiting remarkably large enhancements in fluorescence intensity and quantum yields. The remarkable complexation‐induced pKa shift (ΔpKa=3.3) highlights the strong charge–dipole interaction upon binding. The reversible binding phenomenon can be used for the design of switchable beacons that can be incorporated into cascades of binding networks. This concept is demonstrated herein by three different applications: 1) a switchable fluorescent beacon for chemical sensing of transition metals and other ligands; 2) direct measurement of binding constants between cucurbit[6]uril and various nonfluorescent guest molecules; and 3) quantitative monitoring of biocatalytic reactions and determination of their kinetic parameters. The latter application is illustrated by the hydrolysis of an amide catalyzed by penicillin G acylase and by the elimination reaction of a β‐cabamoyloxy ketone catalyzed by aldolase antibody 38C2. 相似文献
58.
M. B. Das S. Karmakar 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,40(3):339-341
Lifetimes of eight levels belonging to the 5p46d configuration of
singly ionized xenon have been measured by high frequency deflection
technique with a delayed coincidence single photon counting arrangement. The
results have been compared with other experimental and theoretical values.
The lifetimes of the 6d 2F3/2 and 6d 4F3/2 levels have
been measured for the first time. 相似文献
59.
Bikash Karmakar 《Tetrahedron letters》2010,51(20):2748-2750
An efficient, mild and environmentally friendly method has been developed for the Strecker reaction to synthesize α-aminonitriles in the presence of K2PdCl4 as a catalyst. The three-component one-pot condensation of an aldehyde, amine and trimethylsilyl cyanide proceeded smoothly in water to afford the corresponding product in high yield with short reaction times. 相似文献
60.
A single-step melt-quench in situ thermochemical reduction technique has been used to synthesize a new series of Au° nanoparticles embedded antimony glass–ceramic (K2O–B2O3–Sb2O3–ZnO) dichroic nanocomposites. X-ray and selected area electron diffractions manifest growth of Au° nanoparticles along (2 0 0) planes. The particle sizes obtained from X-ray diffraction patterns are found to vary in the range 4–21 nm. Dichroic behavior is attributed to the elliptical shape gold nanoparticles having aspect ratio 1.2, as observed from the transmission electron microscopy (TEM) images. The Au° nanoparticles exhibit surface plasmon resonance band (SPR) around 600 nm, which experiences red-shifts with increasing Au concentration. These nanocomposites when co-doped with Sm2O3 and excited at 949 nm, exhibit 2-fold intensification of 636 nm red emission transition (4G5/2 → 6H9/2) due to SPR induced local field enhancement of Au° nanoparticles and are promising materials for display applications. 相似文献