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Institution

North Eastern Hill University

EducationShillong, Meghalaya, India
About: North Eastern Hill University is a education organization based out in Shillong, Meghalaya, India. It is known for research contribution in the topics: Population & Ruthenium. The organization has 2318 authors who have published 4476 publications receiving 48894 citations.
Topics: Population, Ruthenium, Ligand, Catalysis, Micelle


Papers
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Journal ArticleDOI
TL;DR: The coordination geometry of the complexes strongly influenced the catalytic efficiencies, and the geometry of one of the CuII-OOH intermediates has been optimized by the density functional theory method, and its calculated electronic and vibrational spectra are almost similar to the experimentally observed values.
Abstract: A series of bioinspired copper(II) complexes of N4-tripodal and sterically crowded diazepane-based ligands have been investigated as catalysts for functionalization of the aromatic C-H bond. The tripodal-ligand-based complexes exhibited distorted trigonal-bipyramidal (TBP) geometry (τ, 0.70) around the copper(II) center; however, diazepane-ligand-based complexes adopted square-pyramidal (SP) geometry (τ, 0.037). The Cu-NPy bonds (2.003-2.096 A) are almost identical and shorter than Cu-Namine bonds (2.01-2.148 A). Also, their Cu-O (Cu-Owater, 1.988 A; Cu-Otriflate, 2.33 A) bond distances are slightly varied. All of the complexes exhibited Cu2+ → Cu+ redox couples in acetonitrile, where the redox potentials of TBP-based complexes (-0.251 to -0.383 V) are higher than those of SP-based complexes (-0.450 to -0.527 V). The d-d bands around 582-757 nm and axial patterns of electron paramagnetic resonance spectra [g∥, 2.200-2.251; A∥, (146-166) × 10-4 cm-1] of the complexes suggest the existence of five-coordination geometry. The bonding parameters showed K∥ > K⊥ for all complexes, corresponding to out-of-plane π bonding. The complexes catalyzed direct hydroxylation of benzene using 30% H2O2 and afforded phenol exclusively. The complexes with TBP geometry exhibited the highest amount of phenol formation (37%) with selectivity (98%) superior to that of diazepane-based complexes (29%), which preferred to adopt SP-based geometry. Hydroxylation of benzene likely proceeded via a CuII-OOH key intermediate, and its formation has been established by electrospray ionization mass spectrometry, vibrational, and electronic spectra. Their formation constants have been calculated as (2.54-11.85) × 10-2 s-1 from the appearance of an O (π*σ) → Cu ligand-to-metal charge-transfer transition around 370-390 nm. The kinetic isotope effect (KIE) experiments showed values of 0.97-1.12 for all complexes, which further supports the crucial role of Cu-OOH in catalysis. The 18O-labeling studies using H218O2 showed a 92% incorporation of 18O into phenol, which confirms H2O2 as the key oxygen supplier. Overall, the coordination geometry of the complexes strongly influenced the catalytic efficiencies. The geometry of one of the CuII-OOH intermediates has been optimized by the density functional theory method, and its calculated electronic and vibrational spectra are almost similar to the experimentally observed values.

21 citations

Book ChapterDOI
01 Jan 2010
TL;DR: The review dwells upon these aspects of betel nut induced carcinogenesis to show that genetic susceptibility to cancer through generations progressively increased due to exposure to betelnut.
Abstract: Betel nut is a widely masticated natural product, which is consumed by over 600 million people across the globe. The ancient habit of betel nut chewing, either as dry or raw/wet nut, in association with betel leaf and a host of region specific additives, including chewing tobacco, is believed to be an important etiological factor for human cancer. Alkaloids and their betel nut specific nitrosamine derivatives produced upon metabolic activation interact with DNA and other cellular targets to produce highly variable mutagenic, genotoxic, cytostatic, immunostatic and teratogenic effects. At molecular level the betel nut or its constituents strongly influence gene expression patterns, especially that of tumor suppressor genes. Structural damage to nucleus and mitochondria, etc. are also induced. The review dwells upon these aspects of betel nut induced carcinogenesis to show that genetic susceptibility to cancer through generations progressively increased due to exposure to betel nut.

21 citations

Journal ArticleDOI
15 May 2011
TL;DR: It is revealed that the choleretic effect of salicylate is not due to the influence of salingylate ions on the micellization of NaDC, and the Influence of coanions on the cmc increases almost linearly with temperature.
Abstract: The salicylate ion increases the rate of bile flow (choleretic effect) and bile salts are known to affect the colonic absorption of oxalate. Owing to this physiological relevance of salicylate and oxalate ions, critical micelle concentration (cmc) values of sodium deoxycholate (NaDC) were determined in aqueous sodium oxalate, sodium salicylate, and sodium chloride solutions by using surface tension, fluorescence, and EMF methods. The results indicate, besides a counterion effect, the influence of coanions on the cmc. In the range from 25 to 40 °C, cmc increases almost linearly with temperature. In the temperature range from 30 to 40 °C, the counterion binding constant β of NaDC micelles has the same value (0.17 ± 0.01) in the presence of sodium chloride and sodium salicylate. On the other hand, in sodium oxalate solution β = 0.05 ± 0.02 when oxalate concentration is less than or equal to c* and β = 0.48 ± 0.04 above c*, where c* ≈ 0.038 mol kg−1. EMF measurements also supported this type of counterion binding to NaDC micelles in sodium oxalate solutions. In sodium oxalate solution, at c* a change in the shape of deoxycholate micelles is expected to take place. Salicylate, oxalate, and chloride coanions have a similar effect on the adsorption of NaDC. This study reveals that the choleretic effect of salicylate is not due to the influence of salicylate ions on the micellization of NaDC.

21 citations

Journal ArticleDOI
TL;DR: In this article, a facile general route for substituted and annelated N-H-carbazoles was developed by regiospecific 1,2-addition of 1-carboxy-2-methylindole dianion to acyclic and cyclic α-oxoketene dithioacetals.

21 citations

Journal ArticleDOI
TL;DR: In this paper, the experimental results of the prototype intramolecular proton transfer (ESIPT) system 4-methyl-2,6-diformyl phenol (MFOH) and its derivatives were studied by steady state and time-resolved fluorescence spectroscopy as well as by ab-initio quantum chemical calculation.

21 citations


Authors

Showing all 2368 results

NameH-indexPapersCitations
Vivek Sharma1503030136228
Patrick J. Carroll5850513046
Majeti Narasimha Vara Prasad5622715193
Arun Sharma5537111364
Michael Schmittel5338710461
Birgitta Bergman5218710975
Harikesh Bahadur Singh463077372
Lal Chand Rai401344513
B. Dey403548089
Hiriyakkanavar Ila364075633
Jürgen-Hinrich Fuhrhop352085130
Sreebrata Goswami341423228
Gagan B.N. Chainy331074151
J.P. Gaur31643957
Hiriyakkanavar Junjappa303494102
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
202321
202254
2021352
2020308
2019293
2018306