Heterobi- and multimetallic complexes providing close proximity between several metal centers serve as active species in artificial and enzymatic catalysis, and in model systems, showing unique modes ...of metal-metal cooperative bond activation. Through the rational design of well-defined, unsymmetrical ligand scaffolds, we create a convenient approach to support the assembly of heterometallic species in a well-defined and site-specific manner, preventing them from scrambling and dissociation. In this perspective, we will outline general strategies for the design of unsymmetrical ligands to support heterobi- and multimetallic complexes that show reactivity in various types of heterometallic cooperative bond activation.
Unsymmetrical ligand scaffolds bridging two or more different metals in a site-selective manner offer a convenient approach to utilize metal-metal cooperation for bond activation.
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•Photo, electro-Fenton and photo-electro-Fenton processes were compared for the removal of % color and COD from landfill leachate.•Photo-electro-Fenton process yielded higher % color ...and COD removal with low power consumption than the photo and electro-Fenton process.•Operating parameters were studied to obtain the process efficiency.•Direct and alternating current photo-electro-Fenton process was studied.
The comparison of photo (UV), electro-Fenton and photo-electro-Fenton process on the removal of % color and chemical oxygen demand (COD) along with power consumption on landfill leachate wastewater was investigated. Experimental results showed that, the hybrid photo-electro-Fenton process yielded higher color (100%) and COD (97%) removal efficiencies with lower power consumption (3.10 kWhr/m3) than the photo and electro-Fenton processes alone. Effect of major operating parameters such as current density (0.07–0.35 A/dm2), solution pH (1.5–5), inter-electrode distance (0.75–3 cm), hydrogen per oxide (H2O2) concentration (75–450 mg/L), COD concentration (1000–5000 ppm) and UV power (8–32 W) on the % COD removal efficiency and power consumption of landfill leachate were investigated. The direct and alternating current photo-electro-Fenton process was studied and reported on the % COD removal and power consumption. The alternating current photo-electro-Fenton process is most suitable in comparison to the direct current photo-electro-Fenton process and can be applied effectively and efficiently for the removal of pollutant from wastewater.
India has a rich tradition of plant-based knowledge on healthcare. A large number of plants/plant extracts/decoctions or pastes are equally used by tribals and folklore traditions in India for ...treatment of cuts, wounds, and burns. The present review thus attempts to analyze the ethnobotanical knowledge base for treatment of cuts and wounds which includes a usage of plants, methods employed by tribals and folklore practices prevailing in India. Pharmacological reports available on Indian medicinal plants employing various wound healing models and its underlying molecular mechanism, wherever available, has also been briefly reviewed. This pharmacological validation on Indian medicinal plants is very limited and a large number of plants used in tribal and folklore with enormous potential have not been validated for their wound healing activity. This review therefore attempts to bridge the lacunae in the existing literature and offers immense scope for researchers engaged in validation of the traditional claims and development of safe and effective and globally accepted herbal drugs for cuts and wounds.
Herein, we describe the first transition-metal-free catalytic carboalkoxylation of styrenes with aryl diazonium salts by Meerwein addition in the presence of a phenalenyl ligand at room temperature ...without requiring any light stimulation. This three-component reaction allows facile difunctionalization of styrene derivatives with various alcohols (such as 1, 2, and 3°) as the source of alkoxy group during this transformation. The key intermediates and the transition states involved in this reaction path were unraveled by a series of control experiments coupled with density functional theory calculations. The full mechanistic investigation provides an understanding of the selectivity toward carboalkoxylation (Meerwein arylation addition elimination) in the presence of various alcohols over the simple arylation to multiple bond (Meerwein arylation–elimination) reaction.
The disease preventive and health promotive approach of ‘Ayurveda’, which takes into consideration the whole body, mind and spirit while dealing with the maintenance of health, promotion of health ...and treating ailments is holistic and finds increasing acceptability in many regions of the world. Ancient Ayurvedic physicians had developed certain dietary and therapeutic measures to arrest/delay ageing and rejuvenating whole functional dynamics of the body system. This revitalization and rejuvenation is known as the ‘Rasayan chikitsa’ (rejuvenation therapy). Traditionally, Rasayana drugs are used against a plethora of seemingly diverse disorders with no pathophysiological connections according to modern medicine. Though, this group of plants generally possesses strong antioxidant activity, only a few have been investigated in detail. Over about 100 disorders like rheumatoid arthritis, hemorrhagic shock, CVS disorders, cystic fibrosis, metabolic disorders, neurodegenerative diseases, gastrointestinal ulcerogenesis and AIDS have been reported as reactive oxygen species mediated. In this review, the role of free radicals in these diseases has been briefly reviewed. ‘Rasayana’ plants with potent antioxidant activity have been reviewed for their traditional uses, and mechanism of antioxidant action. Fifteen such plants have been dealt with in detail and some more plants with less work have also been reviewed briefly.
Oxamidato-bridged Re(I)-based hexanuclear trigonal prisms with ester functionality have been synthesised via a multicomponent self-assembly process under solvothermal conditions. The self-assembly of ...Re2(CO)10, oxamide ligands (H2L1 = N,N′-dibutyloxamide, H2L2 = N,N′-dioctyloxamide, H2L3 = N,N′-didodecyloxamide and H2L4 = N,N′-dibenzyloxamide) and phenyl-1,3,5-tris(isonicotinate) (ptin) resulted in the formation of metallaprisms with the general formula {(CO)3Re(μ–η(4)-L)Re(CO)3}3(μ3-ptin)2 (1–4). The metallaprisms 1–4 have been characterised using spectroscopic techniques, and the molecular structure of 4 has been elucidated by single-crystal X-ray diffraction methods. Investigations on the guest binding ability of 2 with a few aromatic alcohols and L-tryptophan using UV–vis and fluorescence spectroscopic titration experiments revealed strong host–guest interactions. The luminescence enhancement studies of 2 and 3 have been carried out using organic-aqueous solvent mixtures.
Herein we report a transition metal free catalytic terminal alkyne functionalization across the C-X triple bond (X = CH and N) with
E
-selective homo (alkyne-alkyne) and head-to-tail selective hetero ...(alkyne-nitrile) dimerization. A series of stoichiometric reactions enabled us to crystallize a reactive organometallic intermediate K-arylacetylide complex which was characterized by X-ray crystallography, indicating that an ionic mechanism is operative.
E
-Selective alkyne-alkyne dimerization as well as terminal alkyne functionalization across the C-N triple bond under transition metal free conditions at room temperature was accomplished.
Nickel perfluoroethyl and perfluoropropyl complexes supported by naphthyridine-type ligands show drastically different aerobic reactivity from their trifluoromethyl analogs resulting in facile oxygen ...transfer to perfluoroalkyl groups or oxygenation of external organic substrates (phosphines, sulfides, alkenes and alcohols) using O
2
or air as a terminal oxidant. Such mild aerobic oxygenation occurs through the formation of spectroscopically detected transient high-valent Ni
III
and structurally characterized mixed-valent Ni
II
-Ni
IV
intermediates and radical intermediates, resembling O
2
activation reported for some Pd dialkyl complexes. This reactivity is in contrast with the aerobic oxidation of naphthyridine-based Ni(CF
3
)
2
complexes resulting in the formation of a stable Ni
III
product, which is attributed to the effect of greater steric congestion imposed by longer perfluoroalkyl chains.
Aerobic oxidation of long-chain perfluoroalkyl Ni complexes results in O-atom transfer to form perfluorocarboxylates
via
high valent Ni; in the presence of external substrate, oxygenation of phosphines, sulfides, stilbenes or alcohols occurs.
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