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991.
New tetra‐ and octasubstituted nitrido(phthalocyaninato)metal(V) complexes RnPcMN (M = Re, Mo, W) were synthesized to obtain soluble nitrido‐bridged phthalocyanines. Phthalocyanines with nitrido bridges between rhenium and boron, aluminium, gallium and indium, respectively, were synthesized from nitrido(tetra‐tert.‐butylphthalocyaninato)rhenium(V) complex, tBu4PcReN and suitable electrophilic reagents like BCl3, B(C6F5)3, BPh3, BEt3, AlCl3, GaCl3, GaBr3, InCl3, etc. The nitrido‐bridged compounds prepared show different stabilities depending on the substituents at the boron atom. Additionally, the possibility to increase the nucleophilicity of (C5H11)8PcWN by reducing this complex with C8K was studied. The reaction of the reduced complex with electrophiles, e.g. with tBuMeSiCl, Ph3SiCl and Me3GeCl indicates the formation of nitrogen‐bridged complexes. 相似文献
992.
993.
Reverse‐phase HPLC method for the quantification of two antihyperglycemic glycolipids in Oplismenus burmannii 下载免费PDF全文
Surjeet Verma Ram Kishor Verma Dibyaranjan Sahoo Santosh Kumar Srivastava 《Biomedical chromatography : BMC》2015,29(11):1675-1681
Glycolipids and sphingolipids are well known for their diverse biological activities like anticancer, anti‐inflammatory, antistress, anti‐HIV, hepatoprotective and antimicrobial. The present study deals with the activity‐guided isolation and characterization of two antihyperglycemic glycolipids, (2S)‐1,2‐di‐O‐octadecanoyl‐3‐O‐[α‐d‐galctopyranosyl‐(1′′ → 6′)‐O‐β‐d‐galactopyranosyl] glycerol (1) and 1‐O‐β‐d‐glucopyranosyl‐(2S,3S,4R,8E)‐2‐[(2R)‐2‐hydroxy‐tetracosanoylamino]‐2,3,4‐octadecanetriol‐8‐ene (2) from Oplismenus burmannii and the development of a simple and validated reverse‐phase HPLC analytical method for their quantification in the methanolic extracts of O. burmannii. The marker compounds 1 and 2 were isolated from the methanolic extract of O. burmannii and characterized on the basis of their spectroscopic data. Their antihyperglycemic potential was evaluated by determining their glucose uptake‐stimulating potential in L6‐GLUT4myc myotube cells. Finally, these analytes were separated on a Waters Spherisorb ODS 2 column with a binary gradient of methanol and water at a constant flow rate of 0.8 mL/min and detected using a photodiode array detector at 230 nm. The calibration curve was linear (r2 > 0.999) over 1.2 orders of magnitude with acceptable accuracy, reproducibility and recovery (98.16–100.50%). The limits of detection and quantification for 1 and 2 were 1.36, 4.11 and 1.11, 3.35 µg/mL respectively. The method is simple, accurate, precise and selective and may be routinely used for the quality control analysis of whole plant extract of O. burmannii for these two glycolipids. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
994.
Abstract —We report here the resonance Raman studies of photooxidation of free base tetraphenylporphin (H2 TPP) in the presence of external electron acceptors such as CCl4 and chloranil under selective laser irradiation. From the dependence of photooxidation on the concentration of electron acceptors, polarity of solvents, excitation lines and temperatures, we have inferred that a weak triplet exciplex formed between the excited H2 TPP and electron acceptor in non-polar solvents serves as transient species and the light-induced intermolecular charge transfer from H2 TPP to the electron acceptor is the primary process involved in photooxidation. Observation of partial photooxidation in the rigid matrix at low temperatures has been interpreted to be due to long-range quantum mechanical electron tunneling process. Almost complete photooxidation is observed in a soft matrix as the donor and acceptor molecules can attain favorable relative orientation and separation for electron transfer during the excited state lifetime of the exciplex. 相似文献
995.
Haider Aiman Khadatkar Priyanka Suresh S. Arisutha S. Verma Sarika 《Journal of Sol-Gel Science and Technology》2021,100(3):375-387
Journal of Sol-Gel Science and Technology - The tooth cavity is the common problem in the enamel surface due to the predominance of the demineralization process. It can be controlled with different... 相似文献
996.
997.
Bryan B. Sauer Peter Avakian Edmund A. Flexman Mimi Keating Benjamin S. Hsiao Ravi K. Verma 《Journal of Polymer Science.Polymer Physics》1997,35(13):2121-2132
Poly(OxyMethylene) (POM) and its miscible blends were studied by multifrequency A.C. dielectric and thermally stimulated currents (TSC). The blends contained small amounts of either poly(vinyl phenol), which is a high glass transition (Tg) diluent, or a styrene-co-hydroxy styrene oligomeric low Tg diluent. The variation of the 10°C “β” transition with blend composition proves that it is the glass transition, and that the −70°C “γ” transition is a local motion. Dielectrically the β transition is very weak in pure POM even in fast-quenched samples. The TSC thermal sampling method also detected two cooperative transitions, γ and β, in POM and its blends, and was used to directly resolve the γ transition into low and high activation energy components. If one considers the contribution of exclusion of the diluents from the crystal lamellae, it is shown that the blends behave like typical amorphous blends as a function of concentration. The effect of crystals on amorphous motions is examined in light of comparison with van Krevelen's37 predictions of an “amorphous” Tg, and the transitions in POM are contrasted with those for other semicrystalline polymers. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2121–2132, 1997 相似文献
998.
Lobana Tarlok S. Verma Renu Singh Randhir Castineiras Alfonso 《Transition Metal Chemistry》1997,23(1):25-28
Reaction of cis-RuCl2(dppp)2 with pyridine-2–thiol (HpyS) in the presence of Et3N in dry benzene replaces both the chloro groups and a diphosphine molecule to form Ru(dppp)(pyS)2 (1) [dppp=Ph2P(CH2)3PPh2], whose crystal and molecular structure has been determined with the help of single crystal X-ray crystallography. The discrete molecules of (1) adopt a distorted octahedral structure containing chelating pyridine-2–thiolato and dppp ligands with trans-S, cis-N and cis-P atom dispositions. The important interatomic parameters are: Ru-S, 2.443(2), 2.339(2); Ru-N, 2.133(5), 2.129(5); Ru-P, 2.274(2), 2.279(2)Å; trans-bond angles, S-Ru-S, 153.89(6); N-Ru-P, 172.76(13), 163.51(14)°; bite angles: P-Ru-P, 90.71(6); N-Ru-S, 67.18(14), 67.72(14)°. The n.m.r. spectra (1H, 13C, 31P) of (1) are also reported in order to compare solution phase behaviour with the solid state structure. The 13C-n.m.r. spectrum of the complex shows the presence of non-equivalent phenyls in the Ph2P-moiety. 相似文献
999.
Deepshikha Yadav Shilpi Verma Jyoti Choudhary Harleen Kaur Pratibha Tiwari Sandeep Singh Pallavi Kushwaha Premshankar K. Dubey Pranjal Chandra Surinder P. Singh 《Electroanalysis》2023,35(4):e202200286
Folic acid (FA) deficiency is associated with several clinical conditions such as megaloblastic anemia, neuropsychiatric, and pregnancy-related syndromes, this makes FA an important metabolite to be monitored. We have fabricated an electrochemical biosensor based on gold nanoparticles decorated molybdenum disulfide nanosheets (AuNPs−MoS2NSs) nanocomposite as a transducer matrix for specific and rapid electrochemical detection of FA. Differential pulse voltammetry (DPV) studies displayed a rapid analytical response of the fabricated AuNPs−MoS2NSs/GCE sensor probe towards FA in a wide concentration range of 0.001–100 μM with a very low detection limit of 0.72±0.03 nM. The selectivity of the fabricated sensor probe has been examined in the presence of interferents such as dopamine, uric acid, ascorbic acid, glucose, and urea. The clinical potential of the fabricated biosensor was established by monitoring FA in human serum samples. The developed AuNPs−MoS2NSs/GCE sensor probe showed high reproducibility and stability, indicating its promise for FA detection in clinical settings. 相似文献
1000.
Dr. Sunglun Kwon Dr. Jie Zhang Dr. Ramesha Ganganahalli Dr. Sumit Verma Prof. Dr. Boon Siang Yeo 《Angewandte Chemie (International ed. in English)》2023,62(16):e202217252
Cu catalysts are most apt for reducing CO(2) to multi-carbon products in aqueous electrolytes. To enhance the product yield, we can increase the overpotential and the catalyst mass loading. However, these approaches can cause inadequate mass transport of CO(2) to the catalytic sites, which will then lead to H2 evolution dominating the product selectivity. Herein, we use a MgAl LDH nanosheet ‘house-of-cards’ scaffold to disperse CuO-derived Cu (OD-Cu). With this support-catalyst design, at −0.7 VRHE, CO could be reduced to C2+ products with a current density (jC2+) of −1251 mA cm−2. This is 14× that of the jC2+ shown by unsupported OD-Cu. The current densities of C2+ alcohols and C2H4 were also high at −369 and −816 mA cm−2 respectively. We propose that the porosity of the LDH nanosheet scaffold enhances CO diffusion through the Cu sites. The CO reduction rate can thus be increased, while minimizing H2 evolution, even when high catalyst loadings and large overpotentials are used. 相似文献