Synthesis, structure and diverse coordination chemistry of cobalt(III) complexes derived from a Schiff base ligand and their biomimetic catalytic oxidation of o-aminophenols

This paper deals with the syntheses and structural characterizations of four new cobalt(III) compounds (1–4) derived from a N3O donor Schiff base ligand and their catalytic activity towards the aerobic oxidation of o-aminophenols. Both counter ions and solvents used for the synthesis have significant influence on structural diversity of the resulting complexes. X-ray crystallography reveals that although the geometry of cobalt(III) centres are octahedral in all the cases but the coordination environments are significantly different in them. All these complexes show diverse reactivity towards the catalytic oxidation of o-aminophenols in which availability of substitutionally labile sites at the metal centre for substrate o-aminophenols binding is the main reason for higher catalytic activity in 2 and 3 than others. Furthermore, we have examined the detailed kinetic studies of the aerobic oxidation of one substituted o-aminophenol, namely 2-amino-5-methylphenol, using 2 and 3 as catalysts in which facile oxidation of the substituted o-aminophenol was noticed. ESI mass spectral study has been carried out in order to get insight into mechanistic pathway of functioning such catalytic activity.publishe

Valence tautomerism induced nucleophilic ipso substitution in a coordinated tetrabromocatecholate ligand and diverse catalytic activity mimicking the function of phenoxazinone synthase

Two new manganese(III) complexes, [pyH][Mn(Br(4)Cat)(2)(PY)1 (1) and [Mn(Br(4)Cat)(Br(3)PYCat)(PY)(2)] (2), where py is pyridine, Br(4)CatH(2) is tetrabromocatechol and Br(3)pyCatH(2) is 3,5,6-tribromo-4-pyridiniumcatechol, derived from redox 'noninnocent' bromo-substituted catecholate ligands are reported. Both complexes were characterized by various spectroscopic techniques in addition to the single crystal X-ray crystallography, and the electrochemical behavior of these complexes was investigated by cyclic voltammetry. Variable temperature UV-vis spectral studies for complex I reveal an unprecedented observation in which a dramatic increase of the ligand-to-metal charge transfer band at 592 nm associated with concomitant change in color of the solution from olive-green to dark-green is noticed with increase in temperature. This unprecedented spectral feature is consistent with the formation of a new species 2 in which valence tautomerism induced aromatic nucleophilic substitution of a tetrabromocatecholate ligand by pyridine is observed. DFT calculations have been used to rationalize this unexpected result. To the best of our knowledge, the nucleophilic aromatic substitution of tetra-bromosemiquinone by pyridine to generate this pyridinium-containing catecholate ligand is the first example of valence tautomerism induced nucleophilic ipso substitution by a nitrogen containing ligand. Although the electrochemical behavior of both complexes is similar, the probable role of a positive charge on the ligand backbone has been discussed in order to justify the significantly higher catalytic activity of complex 2 over complex 1. (C) 2015 Elsevier B.V. All rights reserved

How Did Research on Conservation Agriculture Evolve over the Years? A Bibliometric Analysis

Conservation agriculture has recently been a hot topic of agricultural research and has generated significant global interest. Conservation agriculture has three core principles: minimal soil disturbance, permanent soil cover, and crop rotations. The research on this topic has also witnessed a boom in recent years as the number of peer-reviewed literature on conservation agriculture is rising exponentially. This study critically examines all the peer-reviewed documents published on conservation agriculture from the 1990s to 2021 and indexed in the web of science core database. The search returned 3023 documents, which were then processed in the R-based bibliometric package for annual scientific production trend, source, author, document, citation, keyword analysis, and co-occurrence networking using VOSviewer. Our findings show remarkable growth in conservation agriculture research in recent times, although it witnessed a shortfall in 2021. Notably, 15 core source journals contribute the most to the field, while 8692 researchers have authored or co-authored at least a document on conservation agriculture. While the USA, India, and Australia are front runners in conservation agriculture research, the spread of the topic is worldwide

How Did Research on Conservation Agriculture Evolve over the Years? A Bibliometric Analysis

Conservation agriculture has recently been a hot topic of agricultural research and has generated significant global interest. Conservation agriculture has three core principles: minimal soil disturbance, permanent soil cover, and crop rotations. The research on this topic has also witnessed a boom in recent years as the number of peer-reviewed literature on conservation agriculture is rising exponentially. This study critically examines all the peer-reviewed documents published on conservation agriculture from the 1990s to 2021 and indexed in the web of science core database. The search returned 3023 documents, which were then processed in the R-based bibliometric package for annual scientific production trend, source, author, document, citation, keyword analysis, and co-occurrence networking using VOSviewer. Our findings show remarkable growth in conservation agriculture research in recent times, although it witnessed a shortfall in 2021. Notably, 15 core source journals contribute the most to the field, while 8692 researchers have authored or co-authored at least a document on conservation agriculture. While the USA, India, and Australia are front runners in conservation agriculture research, the spread of the topic is worldwide

Increased levels of interleukin‐10 and IgG3 are hallmarks of Indian Post–kala-azar dermal leishmaniasis

Background. Post-kala-azar dermal leishmaniasis (PKDL), an established sequela of visceral leishmaniasis (VL), is proposed to facilitate anthroponotic transmission of VL, especially during interepidemic periods. Immunopathological mechanisms responsible for Indian PKDL are still poorly defined. Methods. Our study attempted to characterize the immune profiles of patients with PKDL or VL relative to that of healthy control subjects by immunophenotyping, intracellular cytokine staining of peripheral blood mononuclear cells, and enzyme-linked immunosorbent assay for serum cytokines and immunoglobulin G (IgG) subclasses. Results. Patients with PKDL had significantly raised percentages of peripheral CD3+CD8+ cells compared with control subjects, a difference that persisted after cure. Patients with PKDL showed an intact response to phytohemagglutinin, with the percentages of lymphocytes expressing interferon (IFN)-γ, interleukin (IL)-2, IL-4, and IL-10 being comparable to those in control subjects. Patients with VL had decreased IFN-γ and IL-2 expression, which was restored after cure, and increased IL-10 expression, which persisted after cure. In their response to Leishmania donovani antigen, patients with PKDL showed a 9.6-fold increase in the percentage of IL-10-expressing CD3+CD8+ lymphocytes compared with control subjects, and this percentage decreased with treatment. Patients with PKDL had raised levels of IgG3 and IgG1 (surrogate markers for IL-10), concomitant with increased serum levels of IL-10. Conclusions. IL-10-producing CD3+CD8+ lymphocytes are important protagonists in the immunopathogenesis of Indian PKDL