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K.C. Gupta

Bio: K.C. Gupta is an academic researcher from Indian Institute of Technology Roorkee. The author has contributed to research in topics: Schiff base & Metal ions in aqueous solution. The author has an hindex of 11, co-authored 12 publications receiving 1749 citations.

Papers
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Journal ArticleDOI
TL;DR: A review of the catalytic activity of metal complexes of binaphthyl compounds and their combinations with salen Schiff base is presented in this paper, where the pyridyl bis (imide) and pyridine bis(imine) complexes of cobalt(II), iron(II) ions have been used as catalysts in the polymerization of ethylene and propylene.

1,237 citations

Journal ArticleDOI
TL;DR: In this paper, the catalytic activity of different types of Schiff base was analyzed and presented in a review, showing that polymer-supported Schiff base complexes of metal ions show high catalytic performance in comparison to their unsupported analogues.

345 citations

Journal ArticleDOI
TL;DR: The polymer anchored transition metal complexes of N,N′-bis(o-hydroxy acetophenone)ethylene diamine (HPED) Schiff base have shown 85, 86, and 89% comlexation for iron(III), cobalt(II), and nickel(II) ions from solution of metal salts.
Abstract: The polymer anchored transition metal complexes of N,N′-bis(o-hydroxy acetophenone)ethylene diamine (HPED) Schiff base were prepared by reacting N,N′-bis(4-amino-o-hydroxy acetophenone)ethylene diamine (AHPED) Schiff base with cross-linked chloromethylated polystyrene beads and then loading of iron(III), cobalt(II) and nickel(II) ions in methanol. The N,N′-bis (4-amino-o-hydroxy acetophenone)ethylene diamine (AHPED) Schiff base was prepared by nitrosation and reduction of nitrosated HPED Schiff base in presence of Fe/HCl catalyst. The loading of AHPED Schiff base on chloromethylated polystyrene beads was 86% (2.58 mmol g−1 of beads). The AHPED Schiff base anchored polymer beads have shown 85%, 86% and 89% comlexation for iron(III), cobalt(II) and nickel(II) ions from solution of metal salts (2.6 mmol), whereas unsupported HPED Schiff base shown 80%, 88% and 77% comlexation for iron(III), cobalt(II) and nickel(II) ions. The free and polymer supported metal complexes were analyzed for molecular weight (Mw) and composition by elemental analysis. The UV, IR and magnetic measurements of free and polymer supported metal complexes have confirmed the octahedral geometry for iron(III) and square planar geometry for cobalt(II) and nickel(II) ions complexes. The thermogravimetric analysis (TGA) of Schiff base has shown 55% weight loss at 500 °C but iron(III), cobalt(II) and nickel(II) ions complexes have shown 30%, 40% and 48% weight loss at same temperature. The iron(III), cobalt(II) and nickel(II) ions complexes have shown temperature of maximum decomposition rate (Tmax) as 325, 319 and 281 °C, respectively. The unsupported HPED Schiff base complexes of metal ions were found to be less stable although the trend in their thermal stability was almost same. The catalytic activity of free and polymer anchored HPED Schiff base complexes was evaluated by studying the oxidation of phenol at 70 °C. The percent conversion of phenol and turn over number (TON) was found to be optimum at 1:1:1 molar ratio of phenol, H2O2 and metal ions in both free and polymer supported metal complexes. The activation energy for oxidation of phenol by polymer supported HPED Schiff base complex of iron(III) was found to be low (25 kJ mol−1) in comparison to HPED Schiff base complexes of cobalt(II) (57 kJ mol−1) and nickel(II) ions (31 kJ mol−1). On the basis of literature report, a mechanism for oxidation of phenol has been proposed.

81 citations

Journal ArticleDOI
TL;DR: In this article, the anchoring of N,N′-bis(3-ally salicylidene)o-phenylenediamine cobalt(II) Schiff base complex on polymer support has been carried out by suspension copolymerization of synthesized N, N′-bis(3allyl salicyidene),o-nal l-salicylidsene,o-pharmylensiamine monomer Schiff base with styrene (St) and divinylbenzene (DVB) using azob
Abstract: The anchoring of N,N′-bis(3-ally salicylidene)o-phenylenediamine cobalt(II) Schiff base complex on polymer support has been carried out by suspension copolymerization of synthesized N,N′-bis(3-allyl salicylidene)o-phenylenediamine monomer Schiff base (N,N′-BSPDA) with styrene (St) and divinylbenzene (DVB) using azobisisobutyronitrile (AIBN) as initiator in presence of poly(vinyl alcohol). The polymer anchored Schiff base (N,N′-BSPDA) was subsequently loaded with cobalt(II) ions. The cobalt(II) ions loading, degree of cross-linking and swelling in prepared beads have shown dependence on the amount of DVB taken in the reaction mixture. The amount of N,N′-BSPDA monomer Schiff base and its arrangement in cross-linked beads have also shown dependence on the amount of DVB taken in the reaction mixture. The cross-linked beads (Type-III) obtained at 1.50 mmol of DVB have shown highest loading for cobalt(II) ions (1.18 mmol g−1 of beads) due to maximum amount of N,N′-BSPDA monomer Schiff base on these beads (1.74 mmol g−1 of beads). The amount of DVB taken in the reaction mixture has shown significant effect on porosity, internal surface area (SBET), average pore diameter (D) and degree of swelling in prepared beads. The IR, UV and magnetic measurements have provided sufficient evidences for square planar geometry of N,N′-BSPDA cobalt(II) complex both in homogeneous and heterogeneous conditions. The complexation of cobalt(II) ions on polymer anchored N,N′-BSPDA monomer Schiff base has shown a significant increase in its thermal stability. The catalytic activity of polymer supported N,N′-BSPDA cobalt(II) complex was evaluated under different experimental conditions and its activity was compared with unsupported analogue. The energy of activation for decomposition of hydrogen peroxide with supported N,N′-BSPDA cobalt(II) complex has been found to be low (36.04 kJ mol−1) in comparison to unsupported one (61.27 kJ mol−1). To explain experimental results, a suitable rate expression has been derived.

66 citations

Journal ArticleDOI
TL;DR: In this article, N,N′-bis (4amono-o-hydroxy acetophenone) ethylene diamine Schiff base (AHPED) was synthesized by nitrosation and reduction of HPED Schiff and then reacted with cross-linked chloromethylated polystyrene beads in methanol.
Abstract: N,N′-bis (o-hydroxy acetophenone) ethylene diamine Schiff base (HPED) was synthesized to prepare unsupported and polymer supported complexes of iron(III), copper(II) and zinc(II) ions. To immobilize HPED Schiff base on polymer support, first of all N,N′-bis (4-amono-o-hydroxy acetophenone) ethylene diamine Schiff base (AHPED) was synthesized by nitrosation and reduction of HPED Schiff and then reacted with cross-linked chloromethylated polystyrene beads in methanol. The anchoring of HPED Schiff base on polymer beads was 86.21 wt% (2.313 mmol g−1). HPED Schiff base anchored polymer beads were loaded with iron(III), copper(II) and zinc(II) ions, which showed 85.0% (1.96 mmol), 83.0% (1.91 mmol) and 78.0% (1.81 mmol) efficiency for complexation for these metal ions. The unsupported and supported metal complexes were characterized by UV, IR and magnetic measurements, which showed octahedral geometry for iron(III), square planar for copper(II) and tetrahedral for zinc(II) ions complexes. Complexation of metal ions has increased thermal stability of HPED Schiff base. The effect of polymer support on catalytic activity of metal complexes was determined by studying the oxidation of phenol under different experimental conditions in presence of hydrogen peroxide as oxidant. The iron(III) ions complexes showed high activity in comparison to copper(II) and zinc(II) ions complexes. The turn over number (TON) for phenol was high with polymer supported metal complexes than unsupported complexes.

51 citations


Cited by
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Journal ArticleDOI
TL;DR: Biomass is an important feedstock for the renewable production of fuels, chemicals, and energy, and it recently surpassed hydroelectric energy as the largest domestic source of renewable energy.
Abstract: Biomass is an important feedstock for the renewable production of fuels, chemicals, and energy. As of 2005, over 3% of the total energy consumption in the United States was supplied by biomass, and it recently surpassed hydroelectric energy as the largest domestic source of renewable energy. Similarly, the European Union received 66.1% of its renewable energy from biomass, which thus surpassed the total combined contribution from hydropower, wind power, geothermal energy, and solar power. In addition to energy, the production of chemicals from biomass is also essential; indeed, the only renewable source of liquid transportation fuels is currently obtained from biomass.

3,644 citations

Journal ArticleDOI
TL;DR: In the early 1960s, the discovery of crown ethers and spherands by Pedersen, Lehn, and Cram3 led to the realization that small, complementary molecules can be made to recognize each other through non-covalent interactions such as hydrogen-bonding, charge-charge, donor-acceptor, π-π, van der Waals, hydrophilic and hydrophobic interactions to achieve these highly complex and often symmetrical architectures as mentioned in this paper.
Abstract: Fascination with supramolecular chemistry over the last few decades has led to the synthesis of an ever-increasing number of elegant and intricate functional structures with sizes that approach nanoscopic dimensions Today, it has grown into a mature field of modern science whose interfaces with many disciplines have provided invaluable opportunities for crossing boundaries both inside and between the fields of chemistry, physics, and biology This chemistry is of continuing interest for synthetic chemists; partly because of the fascinating physical and chemical properties and the complex and varied aesthetically pleasing structures that supramolecules possess For scientists seeking to design novel molecular materials exhibiting unusual sensing, magnetic, optical, and catalytic properties, and for researchers investigating the structure and function of biomolecules, supramolecular chemistry provides limitless possibilities Thus, it transcends the traditional divisional boundaries of science and represents a highly interdisciplinary field In the early 1960s, the discovery of ‘crown ethers’, ‘cryptands’ and ‘spherands’ by Pedersen,1 Lehn,2 and Cram3 respectively, led to the realization that small, complementary molecules can be made to recognize each other through non-covalent interactions such as hydrogen-bonding, charge-charge, donor-acceptor, π-π, van der Waals, etc Such ‘programmed’ molecules can thus be self-assembled by utilizing these interactions in a definite algorithm to form large supramolecules that have different physicochemical properties than those of the precursor building blocks Typical systems are designed such that the self-assembly process is kinetically reversible; the individual building blocks gradually funnel towards an ensemble that represents the thermodynamic minimum of the system via numerous association and dissociation steps By tuning various reaction parameters, the reaction equilibrium can be shifted towards the desired product As such, self-assembly has a distinct advantage over traditional, stepwise synthetic approaches when accessing large molecules It is well known that nature has the ability to assemble relatively simple molecular precursors into extremely complex biomolecules, which are vital for life processes Nature’s building blocks possess specific functionalities in configurations that allow them to interact with one another in a deliberate manner Protein folding, nucleic acid assembly and tertiary structure, phospholipid membranes, ribosomes, microtubules, etc are but a selective, representative example of self-assembly in nature that is of critical importance for living organisms Nature makes use of a variety of weak, non-covalent interactions such as hydrogen–bonding, charge–charge, donor–acceptor, π-π, van der Waals, hydrophilic and hydrophobic, etc interactions to achieve these highly complex and often symmetrical architectures In fact, the existence of life is heavily dependent on these phenomena The aforementioned structures provide inspiration for chemists seeking to exploit the ‘weak interactions’ described above to make scaffolds rivaling the complexity of natural systems The breadth of supramolecular chemistry has progressively increased with the synthesis of numerous unique supramolecules each year Based on the interactions used in the assembly process, supramolecular chemistry can be broadly classified in to three main branches: i) those that utilize H-bonding motifs in the supramolecular architectures, ii) processes that primarily use other non-covalent interactions such as ion-ion, ion-dipole, π–π stacking, cation-π, van der Waals and hydrophobic interactions, and iii) those that employ strong and directional metal-ligand bonds for the assembly process However, as the scale and degree of complexity of desired molecules increases, the assembly of small molecular units into large, discrete supramolecules becomes an increasingly daunting task This has been due in large part to the inability to completely control the directionality of the weak forces employed in the first two classifications above Coordination-driven self-assembly, which defines the third approach, affords a greater control over the rational design of 2D and 3D architectures by capitalizing on the predictable nature of the metal-ligand coordination sphere and ligand lability to encode directionality Thus, this third strategy represents an alternative route to better execute the “bottom-up” synthetic strategy for designing molecules of desired dimensions, ranging from a few cubic angstroms to over a cubic nanometer For instance, a wide array of 2D systems: rhomboids, squares, rectangles, triangles, etc, and 3D systems: trigonal pyramids, trigonal prisms, cubes, cuboctahedra, double squares, adamantanoids, dodecahedra and a variety of other cages have been reported As in nature, inherent preferences for particular geometries and binding motifs are ‘encoded’ in certain molecules depending on the metals and functional groups present; these moieties help to control the way in which the building blocks assemble into well-defined, discrete supramolecules4 Since the early pioneering work by Lehn5 and Sauvage6 on the feasibility and usefulness of coordination-driven self-assembly in the formation of infinite helicates, grids, ladders, racks, knots, rings, catenanes, rotaxanes and related species,7 several groups - Stang,8 Raymond,9 Fujita,10 Mirkin,11 Cotton12 and others13,14 have independently developed and exploited novel coordination-based paradigms for the self-assembly of discrete metallacycles and metallacages with well-defined shapes and sizes In the last decade, the concepts and perspectives of coordination-driven self-assembly have been delineated and summarized in several insightful reviews covering various aspects of coordinationdriven self-assembly15 In the last decade, the use of this synthetic strategy has led to metallacages dubbed as “molecular flasks” by Fujita,16 and Raymond and Bergman,17 which due to their ability to encapsulate guest molecules, allowed for the observation of unique chemical phenomena and unusual reactions which cannot be achieved in the conventional gas, liquid or solid phases Furthermore, these assemblies found applications in supramolecular catalysis18,19 and as nanomaterials as developed by Hupp20 and others21,22 This review focuses on the journey of early coordination-driven self-assembly paradigms to more complex and discrete 2D and 3D supramolecular ensembles over the last decade We begin with a discussion of various approaches that have been developed by different groups to assemble finite supramolecular architectures The subsequent sections contain detailed discussions on the synthesis of discrete 2D and 3D systems, their functionalizations and applications

2,388 citations

Journal ArticleDOI
TL;DR: Advances in Zr-MOFs since 2008 are summarized and reviewed from three aspects: design and synthesis, structure, and applications to provide guidance for the in-depth investigation of MOFs towards practical applications.
Abstract: Among the large family of metal–organic frameworks (MOFs), Zr-based MOFs, which exhibit rich structure types, outstanding stability, intriguing properties and functions, are foreseen as one of the most promising MOF materials for practical applications. Although this specific type of MOF is still in its early stage of development, significant progress has been made in recent years. Herein, advances in Zr-MOFs since 2008 are summarized and reviewed from three aspects: design and synthesis, structure, and applications. Four synthesis strategies implemented in building and/or modifying Zr-MOFs as well as their scale-up preparation under green and industrially feasible conditions are illustrated first. Zr-MOFs with various structural types are then classified and discussed in terms of different Zr-based secondary building units and organic ligands. Finally, applications of Zr-MOFs in catalysis, molecule adsorption and separation, drug delivery, and fluorescence sensing, and as porous carriers are highlighted. Such a review based on a specific type of MOF is expected to provide guidance for the in-depth investigation of MOFs towards practical applications.

1,692 citations

Journal ArticleDOI
TL;DR: A review of the catalytic activity of metal complexes of binaphthyl compounds and their combinations with salen Schiff base is presented in this paper, where the pyridyl bis (imide) and pyridine bis(imine) complexes of cobalt(II), iron(II) ions have been used as catalysts in the polymerization of ethylene and propylene.

1,237 citations

Journal ArticleDOI
TL;DR: In this article, the synthesis of cyclic carbonates by the 100% atom economical reaction between epoxides and CO2 is reviewed in the context of reducing global emissions of waste CO 2 and converting waste CO2 into industrially useful chemical feedstocks.

1,109 citations