排序方式: 共有71条查询结果,搜索用时 15 毫秒
21.
Murugesan Velayudham Subramanian Singaravadivel Seenivasan Rajagopal Perumal Ramamurthy 《Journal of organometallic chemistry》2009,694(25):4076-4083
Six new homobimetallic and heterobimetallic complexes of rhenium(I) and ruthenium(II) bridged by ethynylene spacer [(CO)3(bpy)Re(BL)Re(bpy)(CO)3]2+ [Cl(bpy)2Ru(BL)Ru(bpy)2Cl]2+ and [(CO)3(bpy)Re(BL)Ru(bpy)2Cl]2+ (bpy = 2,2′-bipyridine, BL = 1,2-bis(4-pyridyl)acetylene (bpa) and 1,4-bis(4-pyridyl)butadiyne (bpb) are synthesized and characterized. The electrochemical and photophysical properties of all the complexes show a weak interaction between two metal centers in heterobimetallic complexes. The excited state lifetime of the complexes is increased upon introduction of ethynylene spacer and the transient spectra show that this is due to delocalization of electron in the bridging ligand. Also, intramolecular energy transfer from *Re(I) to Ru(II) in Re–Ru heterobimetallic complexes occurs with a rate constant 4 × 107 s−1. 相似文献
22.
Effects of addition of P to Co–W coatings from gluconate bath using direct current (DC) and pulse current (PC) methods have been investigated in this study. Co–W–P coatings with different P concentrations are prepared by varying hypophosphite concentration in the bath. Current efficiency of the Co–W–P electrodeposition is lower than that for Co–W coatings. Increase in NaH2PO2 concentration increases the cobalt content significantly and decreases the tungsten content drastically. Co–W–P coatings display ‘cauliflower‐like’ morphology and roughness of the coatings increases with increasing P content. As‐deposited Co–W–P deposits are amorphous while heat treatment at different temperatures has rendered them crystalline with the precipitation of stable species like, Co3W, Co2P, etc. Unlike Co–W coatings, Co–W–P shows two‐step crystallization in differential scanning calorimetry (DSC) and on heat treatment, which is similar to the behavior of Co–P electrodeposited from gluconate baths. Moreover, inclusion of phosphorous and heat treatment have led to significant increase in microhardness of the Co–W–P coatings. X‐ray photoelectron spectroscopy (XPS) studies provide a detailed insight into the nature of Co, W and P species in as‐deposited and sputtered coatings. Microhardness of the heat‐treated coatings is higher than the as‐deposited counterparts and is comparable with that of hard chromium. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
23.
Oxovanadium(IV)‐Salen Ion Catalyzed H2O2 Oxidation of Tertiary Amines to N‐Oxides– Critical Role of Acetate Ion as External Axial Ligand 下载免费PDF全文
Alagarsamy Mathavan Arumugam Ramdass Mohanraj Ramachandran Seenivasan Rajagopal 《国际化学动力学杂志》2015,47(5):315-326
The oxovanadium(IV)‐salen ion catalyzed H2O2 oxidation of N,N‐dimethylaniline forms N‐oxide as the product of the reaction. The reaction follows Michaelis–Menten kinetics and the rate of the reaction is accelerated by electron donating groups present in the substrate as well as in the salen ligand. This peculiar substituent effect is accounted for in terms of rate determining bond formation between peroxo bond of the oxidant and the N‐atom of the substrate in the transition state. Trichloroacetic acid (TCA) shifts the λmax value of the oxidant to the red region and catalyzes reaction enormously. The cleavage of N? O bond by vanadium complex leads to moderate yield of the product. But the percentage yield of the product becomes excellent in the presence of TCA. 相似文献
24.
K. J. Thomas K. George Thomas T. K. Manojkumar Suresh Das M. V. George 《Journal of Chemical Sciences》1994,106(6):1375-1382
A cyanine chromoionophore1 has been synthesised and its photophysical properties have been investigated. Complexation with alkali metal cations (Li+ and Na+) brings about a significant shift in the absorption and emission spectra to shorter wavelengths, which is accompanied by
an enhancement in the fluorescence quantum yield. These effects can be attributed to the suppression of intramolecular charge
transfer processes of the cyanine dye, brought about by complexation with the metal cations.
Dedicated to Professor C N R Rao on his sixtieth birthday
Contribution No. RRLT-PRU-42 from the Regional Research Laboratory, Trivandrum 相似文献
25.
Abhishek Kumar Yadav Manojkumar Jujam Vikas D. Ghule Srinivas Dharavath 《Journal of heterocyclic chemistry》2024,61(3):401-406
A series of five and six-membered C-C bonded energetic materials ( 2 – 7 ) based on a combination of imidazole-triazine and triazole-triazine backbones were designed, synthesized, and characterized using NMR, IR, Mass spectrometry, and TGA-DSC studies. Further, the structure of compound 4 was supported by single-crystal X-ray analysis. All the newly synthesized energetic compounds exhibit good density, excellent thermal stability, good detonation performance, and low mechanical sensitivity toward impact and friction. Among all, the nitrate salt 4 exhibits balanced properties, including high density (1.80 g cm−3), excellent thermal stability (254°C), good detonation velocity (8178 m s−1), and low sensitivity towards impact and friction. The facile synthetic feasibility, thermal stability, energetic performance, and insensitivity of all the molecules suggest they can be used as an insensitive secondary explosive in various defense and civilian applications. 相似文献
26.
An expedient synthesis of 2-deoxy (10) and 3-deoxy (11) cyclohexenyl analogues of 2-deoxy and 3-deoxy-d-ribose sugar from commercially available starting materials is reported. Highly efficient enzymatic resolution of the key compound 10 is described using lipase under hydrolytic conditions. The robust methodology applied here will be useful to synthesize cyclohexenyl nucleosides, which possess potent antiviral activity and are capable of gene silencing via RNAi or antisense applications. 相似文献
27.
James F. Glockner Manojkumar Saranathan Ersin Bayram Christine U. Lee 《Magnetic resonance imaging》2013,31(8):1263-1270
A novel 3D breath-held Dixon fat–water separated balanced steady state free precession (b-SSFP) sequence for MR cholangiopancreatography (MRCP) is described and its potential clinical utility assessed in a series of patients. The main motivation is to develop a robust breath-held alternative to the respiratory gated 3D Fast Spin Echo (FSE) sequence, the current clinical sequence of choice for MRCP. Respiratory gated acquisitions are susceptible to motion artifacts and blurring in patients with significant diaphragmatic drift, erratic respiratory rhythms or sleep apnea. A two point Dixon fat–water separation scheme was developed which eliminates signal loss arising from B0 inhomogeneity effects and minimizes artifacts from perturbation of the b-SSFP steady state. Preliminary results from qualitative analysis of 49 patients demonstrate robust performance of the 3D Dixon b-SSFP sequence with diagnostic image quality acquired in a 20–24 s breath-hold. 相似文献
28.
Padiya KJ Gavade S Kardile B Tiwari M Bajare S Mane M Gaware V Varghese S Harel D Kurhade S 《Organic letters》2012,14(11):2814-2817
The first "In Water" imidazolecarbonylation of amine is described. A one pot reaction of carbonylimidazolide in water with a nucleophile provides an efficient and general method for the preparation of urea, carbamates and thiocarbamates. Use of an anhydrous solvent and an inert atmosphere could be avoided. Product precipitate out from the reaction mixture and can be obtained in high purity by filtration, resulting in a simple and scalable method. 相似文献
29.
A three-dimensional balanced steady-state free precession (b-SSFP)-Dixon technique with a novel group-encoded k-space segmentation scheme called GUINNESS (Group-encoded Ungated Inversion Nulling for Non-contrast Enhancement in the Steady State) was developed. GUINNESS was evaluated for breath-held non-contrast-enhanced MR angiography of the renal arteries on 18 subjects (6 healthy volunteers, 12 patients) at 3.0 T. The method provided high signal-to-noise and contrast renal angiograms with homogeneous fat and background suppression in short breath-holds on the order of 20 s with high spatial resolution and coverage. GUINNESS has potential as a short breath-hold alternative to conventional respiratory-gated methods, which are often suboptimal in pediatric subjects and patients with significant diaphragmatic drift/sleep apnea. 相似文献
30.