Department of Chemistry

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Now showing 1 - 5 of 5
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    Tuning of Catalytic Property Controlled by the Molecular Dimension of Palladium–Schiff Base Complexes Encapsulated in Zeolite Y
    (ACS, 2017) Ray, Saumi
    Planar palladium–Schiff base complexes are synthesized, maintaining the order of their molecular dimensions as PdL1 < PdL2 < PdL3 < PdL4 < PdL5 in free state, as well as encapsulated in zeolite Y, where L1: N,N′-bis(salicylidene)ethylenediamine and L2, L3, L4, and L5 are derivatives of L1. All encapsulated complexes have shown better catalytic activity for the sulfoxidation of methyl phenyl sulfide in comparison to their homogeneous counter parts. These hybrid systems are characterized with the help of different characterization techniques such as X-ray diffraction analysis, scanning electron microscopy–energy-dispersive X-ray spectrometry, X-ray photoelectron spectroscopy, Fourier transform infrared, and UV–visible spectroscopy; all of these studies have suggested that the largest complex deviates by the maximum from its free-state properties, and a radical change in the reactivity of the complex is observed.
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    Palladium–Schiff Base Complexes Encapsulated in Zeolite-Y Host: Functionality Controlled by the Structure of a Guest Complex
    (ACS, 2019) Ray, Saumi
    A series of palladium complexes of tetradendate Schiff base ligands L1 (N,N′-bis(salicylidene)phenylene-1,3-diamine) and its derivatives L2 and L3 have been synthesized by using the “flexible ligand method” within the supercage of zeolite-Y. These complexes in both their free and encapsulated states have been thoroughly characterized with the help of different characterization tools such as XRD, SEM-EDS, BET, thermal analysis, XPS, IR, and UV–vis spectroscopic studies. All these encapsulated complexes are identified with a dramatic red shift of the d–d transition in their electronic spectra when compared with their free states. Theoretical as well as experimental studies together suggest a substantial modification of the structural parameters of square planar Pd(II)–Schiff base complexes upon encapsulation within the supercage of zeolite-Y. Encapsulated complexes are also subject to show modified catalytic activities toward the Heck reaction. These heterogeneous catalysts can easily be separated from the reaction mixture and reused.
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    Room Temperature Ferromagnetic Ni Nanocrystals: An Efficient Transition Metal Platform for Manifestation of Surface-Enhanced Raman Scattering
    (ACS, 2009) Basu, Mrinmoyee
    A simple solid-phase synthetic approach has been deliberately exploited for the synthesis of room temperature ferromagnetic, phase pure, fcc Ni nanocrystals on resin matrix. Self-assembly directed chainlike hierarchical nanostructures on the matrix could be engendered from magnetic dipole−dipole interaction between the nanocrystallites. Then, a practical virtue of the transition metal nanoparticle, Ni, was expressed from the rich and high-quality vibrational information of a chelating ligand, 1,10-phenanthroline (phen), onto the magnetically separated metal particles. Thus, surface-enhanced Raman scattering (SERS) has emerged exclusively from the time-dependent surface complexation of the chemically adhered probe molecule. Finally, kinetic effect has bestowed Ni(II)-phen chelate which later on demonstrates unique SERS activity on fcc Ni nanocrystals. The results provide a benchmark illustration of the value of transition metal for aiding interpretation of the vibrational signature of the adsorbate attainable from SERS studies.
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    Rhodium(III)-Catalyzed Redox-Neutral 1,1-Cyclization of N-Methoxy Benzamides with Maleimides via C–H/N–H/N–O Activation: Detailed Mechanistic Investigation
    (ACS, 2019-02-27) Kumar, Anil
    An Rh(III)-catalyzed 1,1-cyclization of N-methoxy benzamides with maleimides providing isoindolinone spirosuccinimides through N–H/C–H/N–O bond activation is described. The detailed mechanistic investigation including isolation of key metalacycle intermediate, deuterium labeling studies, and DFT calculations were performed. The computational study reveals that the AcOH that formed in the reaction medium plays a key role in the N–OMe bond cleavage and the oxidation of Rh(I) to Rh(III).
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    Tri- and Tetranuclear Copper(II) Complexes Consisting of Mononuclear Cu(II) Chiral Building Blocks with a Sugar-Derived Schiff's Base Ligand
    (ACS, 2006) Sah, Ajay Kumar
    A new sugar-derived Schiff's base ligand N-(3-tert-butyl-2-hydroxybenzylidene)-4,6-O-ethylidene-β-d-glucopyranosylamine (H3L1) has been developed which afforded the coordinatively labile, alcoholophilic trinuclear Cu(II) complex [Cu3(L1)2(CH3OH)(H2O)] (1). Complex 1 has been further used in the synthesis of a series of alcohol-bound complexes with a common formula of [Cu3(L1)2(ROH)2] (R = Me (2), Et (3), nPr (4), nBu (5), nOct (6)). X-ray structural analyses of complexes 2−6 revealed the collinearity of trinuclear copper(II) centers with Cu−Cu−Cu angles in the range of 166−172°. The terminal and central coppers are bound with NO3 and O4 atoms, respectively, and exhibit square-planar geometry. The trinuclear structures of 2−6 can be viewed as the two {Cu(L1)}- fragments capture a copper(II) ion in the central position, which is further stabilized by a hydrogen-bonding interaction between the alcohol ligands and the sugar C-3 alkoxo group. Complex 2 exhibits a strong antiferromagnetic interaction between the Cu(II) ions (J = −238 cm-1). Diffusion of methanol into a solution of complex 1 in a chloroform/THF mixed solvent afforded the linear trinuclear complex [Cu3(L1)2(CH3OH)2(THF)2] (7). The basic structure of 7 is identical to complex 2; however, THF binding about the terminal coppers (Cu−OTHF = 2.394(7) and 2.466(7) Å) has introduced the square-pyramidal geometry, indicating that the planar trinuclear complexes 2−6 are coordinatively unsaturated and the terminal metal sites are responsible for further ligations. In the venture of proton-transfer reactions, a successful proton transfer onto the saccharide C-3 alkoxo group has been achieved using 4,6-O-ethylidene-d-glucopyranose, resulting in the self-assembled tetranuclear complex, [Cu4(HL1)4] (8), consisting of the mononuclear Cu(II) chiral building blocks, {Cu(HL1)}.