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431.
Cai X Majumdar S Fortman GC Cazin CS Slawin AM Lhermitte C Prabhakar R Germain ME Palluccio T Nolan SP Rybak-Akimova EV Temprado M Captain B Hoff CD 《Journal of the American Chemical Society》2011,133(5):1290-1293
The reactivity of a number of two-coordinate [Pd(L)(L')] (L = N-heterocyclic carbene (NHC) and L' = NHC or PR(3)) complexes with O(2) has been examined. Stopped-flow kinetic studies show that O(2) binding to [Pd(IPr)(P(p-tolyl)(3))] to form cis-[Pd(IPr)(P(p-tolyl)(3))(η(2)-O(2))] occurs in a rapid, second-order process. The enthalpy of O(2) binding to the Pd(0) center has been determined by solution calorimetry to be -26.2(1.9) kcal/mol. Extension of this work to the bis-NHC complex [Pd(IPr)(2)], however, did not lead to the formation of the expected diamagnetic complex cis-[Pd(IPr)(2)(η(2)-O(2))] but to paramagnetic trans-[(Pd(IPr)(2)(η(1)-O(2))(2)], which has been fully characterized. Computational studies addressing the energetics of O(2) binding have been performed and provide insight into reactivity changes as steric pressure is increased. 相似文献
432.
Paramjit Kaur Rajeev Mehta Dusan Berek Siddh Nath Upadhyay 《Macromolecular Symposia》2012,315(1):106-111
The ring-opening polymerization (ROP) of L- lactide was carried out in bulk using various initiators along with triphenylphosphine (PPh3) as co-initiator. Equimolar addition of triphenylphosphine increased the molecular masses of polylactide (PLA). The polymerization was carried out at 403.15 K up to 155 hr. Different experiments were carried out over a wide range of monomer to initiator (Mo/Io) ratios. It was found that maximum molecular weight of polylactide was observed when Mo/Io ratio was 2500–2700. Polymerization reactions were carried out under two different environments in the reaction vessel, an inert cover and a partial vacuum. The average molecular weight of polylactide was determined by using size exclusion chromatography. The increase of polymerization time increased the weight average molecular weight but after prolonged reaction time, the molecular weight decreased gradually. 相似文献
433.
D.K. Rai Debjit Datta Sanjay K. Ram Surajit Sarkar Rajeev Gupta Satyendra Kumar 《Solid State Sciences》2010,12(8):1449-1454
Plasma enhanced chemical vapor deposition (PECVD) technique using pulsed-DC power supply was used to fabricate diamond like carbon (DLC) films at deposition rates as high as 110 nm/min. The DLC films deposited by pulsed-DC and DC based power supplies under different gas flow ratios were studied for their suitability as dielectric layer coatings in plasma display panels (PDPs). The effect of deposition parameters on the properties of the DLC films were studied using Fourier transform infra-red spectroscopy (FTIR) and spectroscopic ellipsometry (SE). FTIR reveals that higher hydrogen dilution in gas mixture leads to higher sp3 content. SE studies in wide spectral range were analyzed using Tauc-Lorentz model dielectric function. A rise in the extracted refractive index was seen on increasing the H2 content in the feed gas, thus resulting in optically denser films. Secondary electron emission coefficient (γ) was measured in the films deposited by the DC and pulsed-DC based PECVD. Firing voltage in the DLC samples was found to have very low variation in the operating pressure range used in commercial PDPs, suggesting possibility of enhanced long term reliability of DLC coatings in future PDP applications. 相似文献
434.
The racemic modifications of title natural products 1 and 2 have been synthesised for the first time. The key step was the Au(i)-catalysed conversion of the furanyl-substituted ynone 13 into the annulated furan 14. 相似文献
435.
Lotus seeds are nutraceutically valued natural plant produce, which succumbs to microbial contamination, predominantly to toxigenic moulds. Results of the present study revealed seed coat portion to harbor higher proportion of microbial load, particularly fungi than cotyledon portion. Among the mycotoxins analyzed, aflatoxins (B1, B2, G1 and G2) were below detectable limits, while the seeds were devoid of Ochratoxin-A (OTA). Application of different doses of electron beam and gamma irradiation (0, 2.5, 5, 7.5, 10, 15 and 30 kGy) for decontamination purpose revealed significant dose-dependent decrease in the fungal contaminants (P<0.05). However, the contaminant yeasts could survive up to 10 kGy dose, which could be completely eliminated at 15 kGy. From the results obtained, a dose range between 10 and 15 kGy is recommended for complete decontamination, as these doses have also been shown earlier to have minimal effects on nutritional and functional properties of lotus seeds. 相似文献
436.
The work presents a mathematical model describing the time fractional anomalous-diffusion process of a generalized Stefan problem which is a limit case of a shoreline problem. In this model, the governing equations include a fractional time derivative of order 0 < α ? 1 and variable latent heat. The approximate solution of the problem is obtained by homotopy perturbation method. The results thus obtained are compared graphically with the exact solutions. A brief sensitivity study is also performed. 相似文献
437.
Chandra S Kumar R Singh R 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2006,65(1):215-220
The mixed donor tetradentate (L(1)=N(2)O(2)) and pentadentate (L(2)=N(2)O(2)S) ligands have been prepared by the interaction of 1,3-diaminopropane and thiodiglycolic acid with diamine. These ligands possess two dissimilar coordination sites. Different types of complexes were obtained which have different stoichiometry depending upon the type of ligands. Their structural investigation have been based on elemental analysis, magnetic moment and spectral (ultraviolet, infrared, (1)H NMR, (13)C NMR and mass spectroscopy methods). The Ni(II) complexes show magnetic moments corresponding to two unpaired electrons except [Ni(L(1))](NO(3))(2) which is diamagnetic. Ligand field parameters of these complexes were compared. N(2)O(2)S donor ligand complexes show higher values of ligand field parameters, which are used to detect their geometries. The redox properties and stability of the complexes toward oxidation waves explored by cyclic voltammetry are related to the electron-withdrawing or releasing ability of the substituents of macrocyclic ligands moiety. The Ni(II) complexes displayed Ni(II)/Ni(I) couples irreversible waves associated with Ni(III)/Ni(II) process. 相似文献
438.
Chandra S Kumar R Singh R Jain AK 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2006,65(3-4):852-858
A comparative investigation of the interaction of two pyrrole-substituted, mixed oxygen and nitrogen donor, macrocycles ligands have been designed and their coordination interaction with cobalt(II) is studied. Cobalt(II) salts combine with a tetradentate and hexadentate macrocyclic nitrogen/oxygen donor ligands and formed novel cobalt(II) complexes which are characterized by elemental analysis, molar conductance, magnetic moments, mass, (1)H NMR, IR, electronic and EPR spectral studies. At the room temperature magnetic moment for cobalt(II) complexes lie in the range 4.70-5.01BM, which is higher than the spin-only value. All the complexes are high-spin type and have three unpaired electrons. Therefore, the electronic confutation and the splitting of the orbital will be t(2g)(5)eg(2). The electrochemical behaviour of the cobalt(II) complexes, the Co(III)/Co(II) couple are observed. Their positive potential indicates that metal in lower oxidation state is strongly bound to these ligands. The difference between the potential of the anodic peak and cathodic peak remains constant in all complexes. Also, the ratio between the cathodic peak current and square root of the scan rate is practically constant for the studied complexes. 相似文献
439.
Baisheng Sa Jian Zhou Zhimei Sun Rajeev Ahuja 《Journal of Physics and Chemistry of Solids》2010,71(8):1165-1167
On the basis of an ab initio computational study, the present work provide a full understanding on the atomic arrangements, phase stability as well as electronic structure of Si2Sb2Te5, a newly synthesized phase-change material. The results show that Si2Sb2Te5 tends to decompose into Si1Sb2Te4 or Si1Sb4Te7 or Sb2Te3, therefore, a nano-composite containing Si1Sb2Te4, Si1Sb4Te7 and Sb2Te3 may be self-generated from Si2Sb2Te5. Hence Si2Sb2Te5 based nano-composite is the real structure when Si2Sb2Te5 is used in electronic memory applications. The present results agree well with the recent experimental work. 相似文献
440.