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Dillip Kumar Chand

Bio: Dillip Kumar Chand is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Ligand & Catalysis. The author has an hindex of 28, co-authored 105 publications receiving 2566 citations. Previous affiliations of Dillip Kumar Chand include Nagoya University & University of Tokyo.
Topics: Ligand, Catalysis, Palladium, Denticity, Cryptand


Papers
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Journal ArticleDOI
03 Jul 2017
TL;DR: In this article, a detailed structure-property relationship of the 1-arylidene-1,3-dihydroisobenzofuran dyes is presented in a detailed manner.
Abstract: The present work describes synthesis and photophysical studies of a class of fluorophores containing biologically relevant 1,3-dihydroisobenzofuran scaffold. Ligand-free palladium nanoparticles have been utilized for domino synthesis of 1-arylidene-1,3-dihydroisobenzofurans from 2-iodobenzyl alcohol and terminal arylacetylenes under mild reaction conditions. Reaction of terminal alkylacetylenes with 2-iodobenzyl alcohol however, provided only the Sonogashira products (2-(alk-1-ynyl)phenyl)methanols. The 1-arylidene-1,3-dihydroisobenzofuran derivatives showed structured fluorescence spectra in non-polar cyclohexane, originated from a locally excited state and structureless emission in polar acetonitrile involving intramolecular charge transfer process. The vibronic structures in the locally excited emission were confined to the ring C=C stretching of the dyes. A detailed structure-property relationship of the 1-arylidene-1,3-dihydroisobenzofuran dyes is presented in this study.

4 citations

Journal ArticleDOI
TL;DR: In this article , a pyridine/aniline appended unsymmetrical bis-monodentate ligand N-(3-aminophenyl)nicotinamide, Lun is synthesized via condensation of nicotinic acid with excess m-phenylene diamine.
Abstract: A pyridine/aniline appended unsymmetrical bis-monodentate ligand N-(3-aminophenyl)nicotinamide, Lun is synthesized via condensation of nicotinic acid with excess m-phenylene diamine. A low-symmetry binuclear complex of the Pd2L'2Lun2 type and an extremely rare trinuclear complex of the Pd3Lun6 type are produced by self-assembly of the ligand Lun with cis-protected palladium(II) (i.e., PdL') and palladium(II), respectively. Two isomers (i.e. [(2,0), (2,0)] and [(1,1), (1,1)]-forms) are theoretically possible for the Pd2L'2Lun2-type complex whereas nine isomers can be envisaged in the case of the Pd3Lun6-type arrangement. However, one of the isomers of the Pd2L'2Lun2-type complex as well as the one for the Pd3Lun6-type complex are experimentally obtained. The exclusive formation of specific isomers could be predicted from the 1D/2D NMR study in the solution state and the DFT calculations in the gas phase/implicit solvent media. The formation of the predicted all-(1,1)-[Pd2(en)2Lun2](NO3)4 has been confirmed by a single-crystal XRD study. DFT calculations for the isomers of the Pd3Lun6-type arrangement show that a [cis(2,2), cis(2,2), cis(2,2)] isomer is energetically favourable than the alternatively predicted [trans(2,2), trans(2,2), trans(2,2)] isomer. Conformational changes within the build of the exclusively formed isomers are proposed on the basis of NMR study.

4 citations

Journal ArticleDOI
TL;DR: In this paper, a procedure for practical synthesis of CuNPs from CuSO4·5H2O was established, under appropriate reaction conditions, using rice (Oryza sativa) as an economic source of reducing as well as a stabilizing agent.
Abstract: A procedure for practical synthesis of CuNPs from CuSO4·5H2O is established, under appropriate reaction conditions, using rice (Oryza sativa) as an economic source of reducing as well as a stabilizing agent. Optical and microscopic techniques are employed for the characterization of the synthesized CuNPs and the sizes of the particles were found to be in the range of 8 ± 2 nm. The nanoparticles are used as a catalyst for chemoselective reduction of aromatic nitro compounds to corresponding amines under ambient conditions and water as a reaction medium. CuNPs are synthesized using hydrolysed rice and used as catalyst for chemoselective reduction of nitroarenes to their corresponding amines in water.

4 citations

Journal ArticleDOI
TL;DR: In the solution state, an equimolar mixture of syn- and anti-conformations is present for the ligand N,N′-bis(4-pyridylformyl)piperazine, L. as mentioned in this paper.
Abstract: In the solution state, an equimolar mixture of syn- and anti-conformations is present for the ligand N,N′-bis(4-pyridylformyl)piperazine, L. Combining L with cis-Pd(en)(NO3)2 resulted in the formation of metallomacrocycle cis-[Pd2(en)2(L)2](NO3)4, 1, quantitatively. Coordinated L in complex 1 was found to exist exclusively in the syn-conformation. The equimolar mixture of syn- and anti-conformations was re-established by ethylenediamine induced demetallation of 1.

4 citations

Journal ArticleDOI
TL;DR: In this article , a cost-effective and widely applicable protocols for controlled and predictably selective oxidation of petroleum waste and feedstock ingredients like methyl-/alkylarenes to corresponding value-added carbonyls have been developed, using a surfactant-based oxodiperoxo molybdenum catalyst in water.
Abstract: The synthesis of carbonyl derivatives from renewable feedstocks, by direct oxidation/functionalization of activated and unactivated C(sp3)-H bonds under a controlled and predictably selective fashion, especially in late stages, remains a formidable challenge. Herein, for the first time, cost-effective and widely applicable protocols for controlled and predictably selective oxidation of petroleum waste and feedstock ingredients like methyl-/alkylarenes to corresponding value-added carbonyls have been developed, using a surfactant-based oxodiperoxo molybdenum catalyst in water. The methodologies use hydrogen peroxide (H2O2) as an environmentally benign green oxidant, and the reactions preclude the need of any external base, additive, or cocatalyst and can be operated under mild eco-friendly conditions. The developed protocols show a wide substrate scope and eminent functional group tolerance, especially oxidation-liable and reactive boronic acid groups. Upscaled multigram synthesis of complex steroid molecules by late-stage oxidation proves the robustness and practical utility of the current protocol since it employs an inexpensive recyclable catalyst and an easily available oxidant. A plausible mechanism has been proposed with the help of few controlled experiments and kinetic and computational studies.

4 citations


Cited by
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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: This critical review highlights supermolecular building blocks (SBBs) in the context of their impact upon the design, synthesis, and structure of metal-organic materials (MOMs) by highlighting how the large size and high symmetry of such SBBs can afford improved control over the topology of the resulting MOM and a new level of scale to the resulting framework.
Abstract: This critical review highlights supermolecular building blocks (SBBs) in the context of their impact upon the design, synthesis, and structure of metal–organic materials (MOMs). MOMs, also known as coordination polymers, hybrid inorganic–organic materials, and metal–organic frameworks, represent an emerging class of materials that have attracted the imagination of solid-state chemists because MOMs combine unprecedented levels of porosity with a range of other functional properties that occur through the metal moiety and/or the organic ligand. First generation MOMs exploited the geometry of metal ions or secondary building units (SBUs), small metal clusters that mimic polygons, for the generation of MOMs. In this critical review we examine the recent (<5 years) adoption of much larger scale metal–organic polyhedra (MOPs) as SBBs for the construction of MOMs by highlighting how the large size and high symmetry of such SBBs can afford improved control over the topology of the resulting MOM and a new level of scale to the resulting framework (204 references).

1,554 citations

Journal ArticleDOI
TL;DR: This critical review focuses on developments in the Sonogashira reaction achieved in recent years concerning catalysts, reaction conditions and substrates.
Abstract: The coupling of aryl or vinyl halides with terminal acetylenes catalysed by palladium and other transition metals, commonly termed as Sonogashira cross-coupling reaction, is one of the most important and widely used sp2–sp carbon–carbon bond formation reactions in organic synthesis, frequently employed in the synthesis of natural products, biologically active molecules, heterocycles, molecular electronics, dendrimers and conjugated polymers or nanostructures. This critical review focuses on developments in the Sonogashira reaction achieved in recent years concerning catalysts, reaction conditions and substrates (352 references).

1,246 citations