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1.
J Environ Manage ; 359: 120584, 2024 May.
Article in English | MEDLINE | ID: mdl-38678893

ABSTRACT

Continuous Emission Monitoring Systems (CEMS) are devices used to measure and report real-time emission of air pollutants. Although CEMS have been extensively deployed in developed countries to ensure compliance with emission standards and enhance their environmental performance, their adoption in India is still in its early stages. The present study aims to evaluate the effectiveness of CEMS in India, identify obstacles in terms of policy, regulation, technology and finance that impede their adoption and suggest mechanisms and incentives to facilitate their expansion. The findings indicate that CEMS offer benefits for air pollution control in India by improving monitoring accuracy, transparency, accountability and enforcement. The study also highlights institutional challenges faced by CEMS, including the absence of a certification system, lack of quality assurance measures, issues with data validation and challenges in its calibration as well as integration concerns with existing regulatory framework. To address these challenges effectively it is recommended that India must develop a policy framework for CEMS along with regulations. Essential steps such as establishing a certification and accreditation system should be taken while enhancing stakeholders' capacity and awareness.


Subject(s)
Air Pollutants , Air Pollution , Environmental Monitoring , India , Air Pollution/prevention & control , Air Pollution/analysis , Environmental Monitoring/methods , Air Pollutants/analysis
2.
An Acad Bras Cienc ; 95(suppl 1): e20220964, 2023.
Article in English | MEDLINE | ID: mdl-37466542

ABSTRACT

The present study aimed to identify the bioactive constituents in the chloroform extract of H. spicatum rhizomes (HS-RCLE), further evaluated for its in-vitro pesticidal activities validating via molecular docking techniques. GC/MS analysis of HS-RCLE identified 14 compounds contributing 84.1 % of the total composition. The extract was dominated by oxygenated sesquiterpenes (43.1 %) with curcumenone (25.2 %) and coronarin E (14.8 %) as the major compounds. The extract recorded 89.4 % egg hatchability inhibition and 82.6 % immobility of Meloidogyne incognita, 66.7 % insecticidal activity on Spodoptera litura, 100 % phytotoxic activity on Raphanus raphanistrum seeds, and 74.7 % anti-fungal activity on Curvularia lunata at the respective highest dose studied. The biological activities were furthermore validated by using docking studies on certain proteins/enzymes namely acetylcholinesterase (PBD ID: IC2O), carboxylesterase (PDB ID: 1CI8), acetohydroxyacid synthase (PBD ID: 1YHZ) and trihydroxy naphthalene reductase (PBD ID: 3HNR). The bioactivity of the major constituents of the extract was predicted with the help of in silico PASS studies. HS-RCLE was observed to be a viable alternative source of natural pesticidal agents and paves the way for further studies on its mechanistic approaches and field trials to ascertain its pesticidal studies.


Subject(s)
Pesticides , Zingiberaceae , Chloroform , Molecular Docking Simulation , Acetylcholinesterase , Plant Extracts/pharmacology , Plant Extracts/chemistry
3.
Front Microbiol ; 14: 1170740, 2023.
Article in English | MEDLINE | ID: mdl-37405156

ABSTRACT

A novel laboratory model was designed to study the arsenic (As) biotransformation potential of the microalgae Chlorella vulgaris and Nannochloropsis sp. and the cyanobacterium Anabaena doliolum. The Algae were treated under different concentrations of As(III) to check their growth, toxicity optimization, and volatilization potential. The results revealed that the alga Nannochloropsis sp. was better adopted in term of growth rate and biomass than C. vulgaris and A. doliolum. Algae grown under an As(III) environment can tolerate up to 200 µM As(III) with moderate toxicity impact. Further, the present study revealed the biotransformation capacity of the algae A. doliolum, Nannochloropsis sp., and Chlorella vulgaris. The microalga Nannochloropsis sp. volatilized a large maximum amount of As (4,393 ng), followed by C. vulgaris (4382.75 ng) and A. doliolum (2687.21 ng) after 21 days. The present study showed that As(III) stressed algae-conferred resistance and provided tolerance through high production of glutathione content and As-GSH chemistry inside cells. Thus, the biotransformation potential of algae may contribute to As reduction, biogeochemistry, and detoxification at a large scale.

4.
Front Nutr ; 10: 1180225, 2023.
Article in English | MEDLINE | ID: mdl-37521418

ABSTRACT

Antibiotic resistance poses a serious threat to public health, raising the number of diseases in the community. Recent research has shown that plant-derived phenolic compounds have strong antimicrobial, antifungal, and cytotoxic properties against a variety of microorganisms and work as great antioxidants in such treatments. The goal of the current work is to evaluate the anticancerous, antibacterial, antifungal, antioxidant, and cytotoxicity activities in the extracts of the different plant parts (leaves, stems, and roots) of S. carvifolia (L.) L. This is a medicinally important plant and has been used for different kinds of diseases and ailments such as hysteria and seizures. The phenolic compounds from the different plant parts were analyzed using HPLC and the following were found to be present: chlorogenic acid, gallic acid, rutin, syringic acid, vanillic acid, cinnamic acid, caffeic acid, and protocatechuic acid. Gallic acid was found to have the highest concentration (13.93 mg/g), while chlorogenic acid (0.25 mg/g) had the lowest. The maximum TPC value, which ranged from 33.79 to 57.95 mg GAE/g dry extract weight, was found in the stem. Root extract with 9.4 mg RE/g had the greatest TFC level. In the leaf and stem extracts, the RSC ranged from 0.747 mg/mL to 0.734 mg/1 mL GE/g dry extract weight, respectively. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay was used to measure in vitro antioxidant activity. In a concentration-dependent way, promising antioxidant activity was reported. Moreover, 3,5-dinitrosalicylic acid (DNSA) and the Folin-Ciocalteu phenol reagent technique were used to determine reducing sugar content and total phenolic content, respectively. Antibacterial activity against eight strains (MIC: 250-1,000 µg/mL) was analyzed, and the stem extract exhibited maximum activity. Antifungal activity was also assessed, and potent activity was reported especially in the extract obtained from the stem. Cytotoxicity was evaluated using an MTT assay in the A549 cell line, where different doses (0.0625, 0.125, 0.25, 0.5, and 1 mg/mL) of leaf, root, and stem extracts were used. Treatment with these extracts reduced the cell viability, indicating that S. carvifolia may possess anticancer potential, which can be of great therapeutic value.

5.
Front Pharmacol ; 14: 1099523, 2023.
Article in English | MEDLINE | ID: mdl-36923360

ABSTRACT

Kaempferia, a genus of the family Zingiberaceae, is widely distributed with more than 50 species which are mostly found throughout Southeast Asia. These plants have important ethnobotanical significance as many species are used in Ayurvedic and other traditional medicine preparations. This genus has received a lot of scholarly attention recently as a result of the numerous health advantages it possesses. In this review, we have compiled the scientific information regarding the relevance, distribution, industrial applications, phytochemistry, ethnopharmacology, tissue culture and conservation initiative of the Kaempferia genus along with the commercial realities and limitations of the research as well as missing industrial linkages followed by an exploration of some of the likely future promising clinical potential. The current review provides a richer and deeper understanding of Kaempferia, which can be applied in areas like phytopharmacology, molecular research, and industrial biology. The knowledge from this study can be further implemented for the establishment of new conservation strategies.

6.
Article in English | MEDLINE | ID: mdl-36636605

ABSTRACT

Globba sessiliflora Sims is an aromatic rhizomatous herb of family Zingiberaceae which is endemic to Peninsular India. This study first reports the phytochemical profile and pesticidal potential of oleoresins obtained from the aerial and rhizome parts of Globba sessiliflora Sims. The oleoresins were prepared by the cold percolation method and were analyzed by a gas chromatography-mass spectrometry (GC-MS) method. Both the oleoresins varied greatly in composition, the major compounds identified in aerial part oleoresin (GSAO) were methyl linoleate, methyl palmitate, and phytol, while the major compounds present in rhizome part oleoresin (GSRO) were γ-sitosterol, 8 (17),12-labdadiene-15, 16-dial, methyl linoleate, and methyl palmitate. In order to evaluate the biological activities, the oleoresins were tested under laboratory conditions for nematicidal action and inhibition of egg hatching potential against root knot nematode, where GSRO was more effective. Insecticidal activity was performed against mustard aphid, Lipaphis erysimi and castor hairy caterpillar, Selepa celtis. In case of mustard aphid, GSRO (LC50 = 154.8 ppm) was more effective than GSAO (LC50 = 263.0 ppm), while GSAO (LC50 = 346.7.0 ppm) was more effective against castor hairy caterpillar than GSRO (LC50 = 398.1 ppm). The herbicidal activity was performed in the receptor species Raphanus raphanistrum subsp. sativus, and the oleoresins showed different intensities for seed germination inhibition and coleoptile and radical length inhibition. Molecular docking studies were conducted to screen the in vitro activities and through molecular docking, it was found that the major oleoresins components were able to interact with the binding pocket of HPPD and AChE with γ-sitosterol showing the best binding affinity.

7.
Recent Pat Biotechnol ; 17(2): 106-141, 2023.
Article in English | MEDLINE | ID: mdl-35747965

ABSTRACT

BACKGROUND: This review highlights the folklore, ethnomedicinal uses and conservation status of Caesalpinioideae in Uttar Pradesh (India). AIMS: It aims at compiling available data on traditional medicine, biological activity, phytochemical information and assessing the regional red list status of Caesalpinioideae in Uttar Pradesh. The information provided would help in formulating new drugs and medicines and addressing global conservation issues of such medicinally exploited species. METHODS: The current study included an extensive and systematic review of available literature, the study of previous collections of herbarium specimens, random interviews with locals and tribals, field surveys, and GeoCAT tool-based assessment during 2016-2020. The study reports that the majority of species of Caesalpinioideae are used for curing digestive problems (about 20 species) and skin diseases (19 species). RESULTS: Almost all the species have antimicrobial and antioxidant properties. These pharmacological activities can be attributed to the presence of various types of anthraquinones in plants. CONCLUSION: The regional conservation status reveals that eight species qualified for the status of regionally threatened category while two species fall under the near threatened category.


Subject(s)
Fabaceae , Plants, Medicinal , Plants, Medicinal/chemistry , Ethnopharmacology , Ethnobotany , Phytotherapy , Health Knowledge, Attitudes, Practice , Patents as Topic , India
8.
Curr Pharm Biotechnol ; 24(9): 1094-1107, 2023.
Article in English | MEDLINE | ID: mdl-36200220

ABSTRACT

The genus Ocimum comprises many species widely cultivated in different parts of the world for their pharmaceutical, neutraceutical and other commercial importance. Many biological activities such as antimicrobial, cytotoxic, anti-nociceptive, anti-inflammatory, hypoglycaemic, hepatoprotective and antioxidant have been ascribed to Ocimum, which can be linked to the occurrence of biologically active phytochemicals like phenolic acids, essential oil, flavonoids, and terpenes hence making it a potential source for discovery and development of novel drugs. The present review covers the successive advances in the traditional medicinal aspects, phytochemistry, bioactivities and the bioavailability of four Ocimum species, i.e., Ocimum basilicum L., Ocimum sanctum L., Ocimum gratissimum L. and Ocimum tenuiflorum L., to explore their applications in versatile industries. Furthermore, this thorough compilation will be used as a potential resource for further Ocimum-related medication development and research and to identify the research gaps to fill.


Subject(s)
Anti-Infective Agents , Ocimum basilicum , Ocimum , Oils, Volatile , Oils, Volatile/pharmacology , Oils, Volatile/therapeutic use , Phytochemicals/pharmacology , Phytochemicals/therapeutic use , Plant Extracts/pharmacology , Plant Extracts/therapeutic use
9.
Diseases ; 10(4)2022 Nov 28.
Article in English | MEDLINE | ID: mdl-36547200

ABSTRACT

Cancers are the leading cause of death, causing around 10 million deaths annually by 2020. The most common cancers are those affecting the breast, lungs, colon, and rectum. However, it has been noted that cancer metastasis is more lethal than just cancer incidence and accounts for more than 90% of cancer deaths. Thus, early detection and prevention of cancer metastasis have the capability to save millions of lives. Finding novel biomarkers and targets for screening, determination of prognosis, targeted therapies, etc., are ways of doing so. In this review, we propose various sialyltransferases and neuraminidases as potential therapeutic targets for the treatment of the most common cancers, along with a few rare ones, on the basis of existing experimental and in silico data. This compilation of available cancer studies aiming at sialyltransferases and neuraminidases will serve as a guide for scientists and researchers working on possible targets for various cancers and will also provide data about the existing drugs which inhibit the action of these enzymes.

10.
Molecules ; 27(15)2022 Jul 28.
Article in English | MEDLINE | ID: mdl-35956784

ABSTRACT

Hedychium coccineum Buch. Ham. ex Sm. is a perennial rhizomatous herb belonging to the family Zingiberaceae. The aim of the present study was to compare the chemical composition and biological activities of H. coccineum rhizome essential oil (HCCRO) and H. coccineum aerial part essential oil (HCCAO). The plant material was subjected to hydro-distillation using Clevenger's apparatus in order to obtain volatile oil and analyzed for its chemical constituents using GC-MS. The comparative study of the rhizome and aerial part essential oils of H. coccineum displayed that (E)-nerolidol (15.9%), bornyl acetate (13.95%), davanone B (10.9%), spathulenol (8.9%), and 1, 8-cineol (8.5%) contributed majorly to the HCCRO, while 7-hydroxyfarnesen (15.5%), α-farnesene (11.1%), α-pinene (10.9%), spathulenol (7.7%), and ß-pinene (6.8%) were present as major constituents in the HCCAO. Both the essential oils were studied for their biological activities, such as nematicidal, insecticidal, herbicidal, antifungal, and antibacterial activities. The essential oils exhibited significant nematicidal activity against Meloidogyne incognita, insecticidal activity against Spodoptera litura, and moderate herbicidal activity against R. raphanistrum sub sp. sativus, and good antifungal activity against Fusarium oxysporum and Curvularialunata. Essential oils were also tested for antibacterial activity against Staphylococcus aureus and Salmonella enterica serotype Typhi. Both oils showed good to moderate activity against the tested pathogens. The significant nematicidal, insecticidal, herbicidal, antifungal, and antibacterial activities of both the essential oils might be helpful for the development of environmentally friendly pesticides that could be an alternative to synthetic pesticides in the future.


Subject(s)
Insecticides , Oils, Volatile , Zingiberaceae , Anti-Bacterial Agents/chemistry , Anti-Bacterial Agents/pharmacology , Antifungal Agents/pharmacology , Antinematodal Agents , Microbial Sensitivity Tests , Oils, Volatile/chemistry , Oils, Volatile/pharmacology , Plant Oils , Zingiberaceae/chemistry
11.
Nanomaterials (Basel) ; 12(9)2022 Apr 26.
Article in English | MEDLINE | ID: mdl-35564176

ABSTRACT

Perovskite solar cells (PSCs) have achieved significantly high power-conversion efficiency within a short time. Most of the devices, including those with the highest efficiency, are based on a n-i-p structure utilizing a (doped) spiro-OMeTAD hole transport layer (HTL), which is an expensive material. Furthermore, doping has its own challenges affecting the processing and performance of the devices. Therefore, the need for low-cost, dopant-free hole transport materials is an urgent and critical issue for the commercialization of PSCs. In this study, n-i-p structure PSCs were fabricated in an ambient environment with cuprous iodide (CuI) HTL, employing a novel transfer-printing technique, in order to avoid the harmful interaction between the perovskite surface and the solvents of CuI. Moreover, in fabricated PSCs, the SnO2 electron transport layer (ETL) has been incorporated to reduce the processing temperature, as previously reported (n-i-p) devices with CuI HTL are based on TiO2, which is a high-temperature processed ETL. PSCs fabricated at 80 °C transfer-printing temperature with 20 nm iodized copper, under 1 sun illumination showed a promising efficiency of 8.3%, (JSC and FF; 19.3 A/cm2 and 53.8%), which is comparable with undoped spiro-OMeTAD PSCs and is the highest among the ambient-environment-fabricated PSCs utilizing CuI HTL.

12.
Transl Oncol ; 22: 101458, 2022 Aug.
Article in English | MEDLINE | ID: mdl-35607455

ABSTRACT

SARS-CoV-2 is a single-stranded RNA virus that has caused the ongoing COVID-19 pandemic. ACE2 and other genes utilized by SARS-CoV-2 to enter human cells have been shown to express in Head and Neck Squamous Cell Carcinoma (HNSCC) patients. However, their expression pattern in different subtypes has not been investigated. Hence, in the current study, we have analyzed the expression of ACE2, TMPRSS2 and FURIN in 649 HNSCC patients from two independent cohorts. Our analysis showed significantly lower expression of TMPRSS2 while significantly increased expression of ACE2 and FURIN in HPV-negative HNSCC. Comparison of expression of these genes in the three subtypes of HNSCC patients (basal, classical and inflamed/mesenchymal) showed no significant difference in the expression of ACE2 among the three subtypes; however, the basal subtype showed significantly reduced expression of TMPRSS2 but significantly increased expression of FURIN. Comparison of expression of these genes between the HPV-negative patients of basal subtype vs all others confirmed significantly lower expression of TMPRSS2 in HPV-negative patients of basal subtype as compared to all others. Our study shows that the different subtypes of HNSCC patients have different expression patterns of genes utilized by the SARS-CoV-2 to enter human cells, and hence, their susceptibility to SARS-CoV-2 may also be different. As the expression of TMPRSS2 is significantly lower in the HNSCC patients of the basal subtype, we predict that these patients would be less susceptible to SARS-CoV-2 infection than the patients of other subtypes. However, these findings need to be further validated.

13.
J Genet Eng Biotechnol ; 20(1): 63, 2022 Apr 22.
Article in English | MEDLINE | ID: mdl-35451659

ABSTRACT

BACKGROUND: DNA barcoding is a powerful method for phylogenetic mapping and species identification. However, recent research has come to a consistent conclusion about the universality of DNA barcoding. We used matK and rbcL markers to test the universality of twelve accessions from different locations belonging to two Selinum species, Selinum tenuifolium Wall. C. B. Clarke and Selinum vaginatum C. B. Clarke, keeping in mind their ability to identify species and establish phylogenetic relationships within and between the accessions. RESULTS: The success rates of PCR amplification using matK and rbcL were 75.26% ± 3.65% and 57.24% ± 4.42%, and the rate of DNA sequencing was 63.84% ± 4.32% and 50.82% ± 4.36%, respectively, suggesting that success rates of species identification of the two fragments were higher than 41.00% (matK, 41.50% ± 2.81%; rbcL, 42.88% ± 2.59%), proving that these fragments might be used to identify species. The best evolutionary tree with good supporting values was produced utilizing combinations of matK + rbcL markers when phylogenetic relationships were built with random fragment combinations. The twelve accessions of Selinum collected from different locations and their molecular sequences of matK and rbcL markers were blasted with other genera of Apiaceae family, and it was found that Selinum is most closely related to Angelica species of Apiaceae family. CONCLUSION: The present study has grouped twelve accessions of Selinum species using molecular markers into phylogenies, which is first-of-its-kind report that established interrelationships within different species of Apiaceae with respect to Selinum.

14.
Curr Pharm Biotechnol ; 23(9): 1132-1141, 2022.
Article in English | MEDLINE | ID: mdl-34387162

ABSTRACT

BACKGROUND: Pinus belongs to the family Pinaceae, represented by several species across the globe. Various parts of the plant including needles are rich in biologically active compounds, such as thunbergol, 3-carene, cembrene, α-pinene, quercetin, xanthone. Of all the alkaloids, the piperidine group is one of the important component and holds considerable medicinal importance. METHODS: The group of alkaloids was initially identified from the genus Piper through which a large variety of piperidine molecules have been extracted. The planar structure of this heterocyclic nucleus enables acetamide groups to be added at various ring configurations. RESULTS: Piperidines have gained considerable importance. The broad range of its therapeutic application has paved a way for researchers to implant the nucleus from time to time in diversified pharmacophores and establish new profile. DISCUSSION: Biological functions of piperidine metabolites have been mostly examined on a limited scale, and that most of the findings are preliminary. We have tried to present various clinical applications of piperidine alkaloids in this study that researchers have already attempted to demystify with time. CONCLUSION: We have also illustrated different types of piperidine structures and their sources in different members of the family Pinaceae with special emphasis on Pinus. Given the importance of the piperidine nucleus, the study will enable the researchers to produce scaffolds of highest therapeutic efficacy.


Subject(s)
Alkaloids , Pinus , Alkaloids/chemistry , Alkaloids/pharmacology , Pinus/chemistry , Piperidines/chemistry , Piperidines/pharmacology , Plant Extracts/chemistry , Plant Extracts/pharmacology
15.
Braz. J. Pharm. Sci. (Online) ; 58: e201031, 2022. tab, graf
Article in English | LILACS-Express | LILACS | ID: biblio-1420397

ABSTRACT

Abstract This study was aimed to explore the chemical composition and biological activities of essential oil from aerial part of Mosla dianthera along with its major isolated compound, carvone. The hydro-distilled essential oil was analysed by GC-MS and biological activities were investigated in terms of antioxidant, anti-inflammatory, herbicidal, antibacterial, anti-fungal and anti-feedant properties. GC-MS analysis led to the identification of forty-nine components contributing 96.2% of essential oil with carvone (41.9%) as the most abundant constituent. The oil and carvone showed good to moderate antioxidant potentials determined by radical scavenging, reducing power and metal chelating activities. Carvone showed good anti-inflammatory activity (78.0%) compared to essential oil (74.2%). Both essential oil and carvone exhibited excellent herbicidal activity against Raphanus raphanistrum subsp. sativus seeds. The essential oil and carvone showed significant anti-bacterial efficacy against Bacillus cereus and Escherichia coli. It was observed that essential oil showed strong antifungal property than carvone against Alternaria alternata and Curvularia lunata. Both the samples exhibited anti-feedant activity in a dose dependent manner against third instar larvae of Spilosoma obliqua. Results obtained revealed the possible applications of essential oil and carvone as a bioactive source of natural antioxidants, excellent herbicide and an effective substance for antifungal and antifeedant activities.

16.
Braz. arch. biol. technol ; 65: e22210034, 2022. tab, graf
Article in English | LILACS-Express | LILACS | ID: biblio-1364450

ABSTRACT

Abstract: Bemisia tabaci (Asia II 5) and Trialeurodes vaporariorum are the two devastating species of whiteflies infesting a wide range of vegetable crops in the North-Western Himalayan region. Therefore, the present investigation deals with a comparative study of the morphology and developmental biology of these two whitefly species. The total developmental period from egg to adult was 22.82 and 23.40 days for B. tabaci (Asia II 5) and T. vaporariorum, respectively, which did not differ significantly. The adult longevity, fecundity, and adult emergence in T. vaporariorum is quite higher than B. tabaci (Asia II 5) which were observed as 10.40 days, 118.00 eggs/female, 90.69 per cent and 6.80 days, 73.33 eggs/female, 86.59 per cent, respectively. Similarly, the egg hatching and the survival rate is higher in T. vaporariorum than in B. tabaci (Asia II 5) (95.11, 81.44 per cent and 91.68, 78.09 per cent). Morphological characters such as marginal setae, abdominal setae, vasiform orifice, lingula, and antennae, which were reliable characters for the identification of both whitefly species and diagnostics of the two whiteflies, were explicated in a comparative discussion.

17.
Adv Mater ; 33(47): e2005932, 2021 Nov.
Article in English | MEDLINE | ID: mdl-34013605

ABSTRACT

Structuring Si, ranging from nanoscale to macroscale feature dimensions, is essential for many applications. Metal-assisted chemical etching (MaCE) has been developed as a simple, low-cost, and scalable method to produce structures across widely different dimensions. The process involves various parameters, such as catalyst, substrate doping type and level, crystallography, etchant formulation, and etch additives. Careful optimization of these parameters is the key to the successful fabrication of Si structures. In this review, recent additions to the MaCE process are presented after a brief introduction to the fundamental principles involved in MaCE. In particular, the bulk-scale structuring of Si by MaCE is summarized and critically discussed with application examples. Various approaches for effective mass transport schemes are introduced and discussed. Further, the fine control of etch directionality and uniformity, and the suppression of unwanted side etching are also discussed. Known application examples of Si macrostructures fabricated by MaCE, though limited thus far, are presented. There are significant opportunities for the application of macroscale Si structures in different fields, such as microfluidics, micro-total analysis systems, and microelectromechanical systems, etc. Thus more research is necessary on macroscale MaCE of Si and their applications.

18.
Dalton Trans ; 50(3): 869-879, 2021 Jan 21.
Article in English | MEDLINE | ID: mdl-33237067

ABSTRACT

The rhodium complex Rh(HL)(COD)Cl, 1, L being a functionalized N-heterocyclic carbene (NHC) ligand with an oxygen-containing pendant arm, has been used as the entry point to synthesize a series of neutral and cationic Rh(i) O,C chelates. While the Rh-carbene interaction is similar in all these 16-electron complexes, structural analysis reveals that the strength of the Rh-O bond is greatly affected by the nature of the O-donor: R-O- > R-OH > R-OBF3. These subtle changes in the nature of the O-containing tether are found to be responsible for large differences in the alkene hydrosilylation catalytic activity of these compounds: the stronger the Rh-O interaction, the better the catalytic performances. The most active catalyst, [Rh(L)(COD)], 2, demonstrated good catalytic activity under mild reaction conditions for the hydrosilylation of a range of alkene substrates with the industrially relevant non-activated tertiary silane, 1,1,1,3,5,5,5-heptamethyltrisiloxane (MDHM). Furthermore, this complex is an effective catalyst for the selective remote functionalization of internal olefins at room temperature via tandem alkene isomerization-hydrosilylation.

19.
Indian J Labour Econ ; 63(Suppl 1): 79-86, 2020.
Article in English | MEDLINE | ID: mdl-32929315

ABSTRACT

The paper examines the nature of the migrant crisis in India after the country-wide lockdown in March 2020 and brings out the types of labour migrants who were severely adversely affected by the lockdown, leading to their exodus towards their native villages. It further assesses the government's response and proposes some key policy imperatives.

20.
Dalton Trans ; 49(10): 3120-3128, 2020 Mar 09.
Article in English | MEDLINE | ID: mdl-32096534

ABSTRACT

We report the synthesis and characterization of a series of original tantalum/rhodium heterobimetallic species assembled by a bifunctional alkoxy-N-heterocyclic carbene (NHC) ligand platform (noted L). The heterotrimetallic [Ta(CH2tBu)(CHtBu)(µ-L)Rh2(COD)2Cl2]n, 2, and heterobimetallic [Ta(µ-L)(CHtBu)(CH2tBu)2Rh(COD)Cl], 4, complexes are obtained upon treatment of [Ta(L)(CHtBu)(CH2tBu)2], 1, with [Rh(COD)Cl]2. To avoid parasistic reactivity arising from the neopentylidene fragment in 1, the peralkyl compound {Ta(L)[OSi(OtBu)3](CH2tBu)3}, 5, resulting from the 1,2-addition of tris(tertbutoxysilanol) across the Ta[double bond, length as m-dash]C alkylidene motif, is prepared. An unanticipated silanol-NHC adduct, {HOSiOtBu3}{Ta(L)[OSi(OtBu)3](CH2tBu)3}, 6, is formed when 1 is treated with two equivalents of HOSi(OtBu)3. Finally, treatment of 5 with [Rh(COD)Cl]2 provides the heterobimetallic complex {Ta(µ-L)[OSi(OtBu)3](CH2tBu)3Rh(COD)(Cl)}, 7, in high yield. This work highlights the reactivity of Ta-NHC adducts and the aptitude of the NHC motif to transfer from Ta to Rh which is used with profit as an efficient synthetic route to access early/late heterobimetallic complexes.

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