Department of Chemistry
Permanent URI for this collectionhttp://localhost:4000/handle/123456789/1924
Browse
13 results
Search Results
Item Template effect of innocent and coordinating anions on the formation of interpenetrated 2D and 3D networks: methyl orange and iodine sorption studies(RSC, 2020) Sarkar, MadhushreeA 2D Cd(II) coordination polymer [Cd2(L1)4(H2O)4][ClO4]4·5(H2O), CP1, was synthesized with 2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene (L1) while the use of benzene-1,3-disulphonate (L2) along with L1 resulted in a novel 3D Cd(II) coordination polymer, [Cd(L1)2(L2)]·2(H2O)·(CH3OH), CP2. CP1 attained a threefold interpenetrated 2D staircase network where the channels are filled with H2O and ClO4− anions. CP2 has a 3D interpenetrated structure and has small pores. The chemical nature and size of the pores of CP1 and CP2 are effective in adsorbing organic dye molecules. Selective adsorption of upto 96% of methyl orange (MO) within 10 min was observed in CP1 and CP2. CP2 was also studied for the adsorption and desorption of iodine. CP1 and CP2 showed luminescence and their solid state PL has a strong emission peak at ∼484 nm. The structural analysis of L1 and [HL1][ClO4] showed the effect of ClO4− on the supramolecular assembly and geometry of the molecules of L1.Item Carbene-Mediated Transformations of 1-(Benzylideneamino)benzimidazoles(ACS, 2011-04-11) Sakhuja, RajeevCarbene-mediated transformations of N-(3-butylbenzimidazol-3-ium-1-yl)-1-arylmethanimine iodides with carbon disulfide and benzoyl isothiocyanate gave the corresponding NHC·CS2 betaines in 68−85% and benzoyl-[1-butyl-3-[(E)-(aryl)methyleneamino]benzimidazol-1-ium-2-carbothioyl]azanides, respectively, in 74−85% yields. However, reaction with excess isopropyl isothiocyanate in NaH/THF at room temperature yielded the 1-butyl-1′,3′-diisopropyl-3-[(E)-(aryl)methyleneamino]spiro[benzimidazole-2,5′-imidazolidine]-2′,4′-dithiones (74−77%).Item The Chemistry of N-Hydroxyamidoximes, N-Aminoamidoximes, and Hydrazidines(ACS, 2012-02-27) Sakhuja, RajeevN-Hydroxyamidoximes, N-aminoamidoximes, and hydrazidines belong to a class of compounds with the general formula RC═NX(NHY) where X = OH or NH2, Y = OH or NH2, and R is a linear side chain, carbocycle residue, or heterocycle residue. Their structures are similar to those of amidoximes and amidrazones, but they possess very different synthetic utility and pharmacological properties. There are several reviews published on the synthetic and biological applications of amidrazones and amidoximes. (1-8) However, a comprehensive review on the preparative methods, synthetic utility, and biological applications is missing for this class of compounds thus far. We now attempt to readdress the situation by providing a detailed compilation on the chemistry of N-hydroxyamidoximes, N-aminoamidoximes, and hydrazidines in terms of the structure, preparative methods, reactivity, and biological applications.Item Scaffold-Hopping Strategy: Synthesis and Biological Evaluation of 5,6-Fused Bicyclic Heteroaromatics To Identify Orally Bioavailable Anticancer Agents(ACS, 2011-03-24) Shukla, ParitoshUtilizing a scaffold-hopping drug-design strategy, we sought to identify a backup drug candidate for BPR0L075 (1), an indole-based anticancer agent. For this purpose, 5,6-fused bicyclic heteroaromatic scaffolds were designed and synthesized through shuffling of the nitrogen from the N-1 position or by insertion of one or two nitrogen atoms into the indole core of 1. Among these, 7-azaindole core 12 showed potent in vitro anticancer activity and improved oral bioavailability (F = 35%) compared with 1 (F < 10%).Item An Aminolytic Approach toward Hierarchical β-Ni(OH)2 Nanoporous Architectures: A Bimodal Forum for Photocatalytic and Surface-Enhanced Raman Scattering Activity(ACS, 2010) Basu, MrinmoyeeA surfactantless, trouble-free, and gentle wet chemistry approach has been used to interpret the precisely controlled growth of β-Ni(OH)2 with the assistance of ammonia and nickel acetate from seedless mild hydrothermal conditions. A thorough investigation of the reaction kinetics and product morphology with varied concentration of NH3 and different reaction times suggests that a putative mechanism of dissolution, recrystallization, and oriented attachment supports the intelligent self-assembly of nanobuilding blocks. Associated characterizations (FTIR, PXRD, FESEM, EDAX, HRTEM, and Raman) have identified it to be pure β-Ni(OH)2 without any signature of contamination. The assembled units result in porous frameworks (nanoflowers and nanocolumns) and are indeed full of communally intersecting nanopetals/nanoplates with both lengths and widths on the order of micrometer to nanometer length scale. The as-synthesized material could also be used as a precursor for nanometric black NiO under calcination. The hydroxide has been found to be a potent and environmentally benign material because it warrants its photocatalytic activity through dye mineralization. Finally, Ni(OH)2 has been photochemically derivatized with dosages of silver nanoparticles bringing a competent composite authority Ag@Ni(OH)2, to give a full-proof enhanced field effect of prolific SERS activity. In a nutshell, these results are encouraging and fetch new promise for the fabrication of a low-cost and high-yielding greener synthetic protocol for a functional material with promising practicability.Item Crystal Engineering of Metal−Organic Frameworks Containing Amide Functionalities: Studies on Network Recognition, Transformations, and Exchange Dynamics of Guests and Anions(ACS, 2007-06-07) Sarkar, MadhushreeThe reactions of bis(pyridinecarboxamido)alkanes with copper(II) in the presence of various anions and solvent systems afforded several polymeric crystalline complexes with or without guest inclusion. The crystal structure analyses of these complexes reveal that the coordination networks observed here include open one-dimensional (1D) chains containing cavities and open (4,4)-networks with three types of packing modes, namely, mixed, offset−offset, and trigonal, doubly interpenetrated (4,4)-networks both in parallel and in perpendicular (diagonal/diagonal) modes and a three-dimensional pseudo-diamondoid (658-topology) network. The self-complementary amide groups of the ligands assembled these coordination networks into higher dimensional architectures via N−H···O hydrogen bonds. The exchange of counteranions from the polymeric crystalline complexes was found to trigger the network transformations. The 1D chain, which has rectangular cavities, was transformed into a pseudo-diamondoid network upon exchange of ClO4- with PF6- anions. The exchange of anions from two-dimensional (2D) open (4,4)-networks resulted in 2D-interpenetrated networks. It was found that the reverse exchange that is expected to result in open networks from interpenetrated networks is not allowed. The guest molecules included in these networks range from small molecules such as H2O, EtOH, and CHCl3 to big aromatic molecules such as nitrobenzene, toluene, anisole, p-xylene, benzonitrile, and naphthalene. The exchange of guest molecules in crystal-to-crystal fashion was also found to trigger the transformations in the mode of packing of 2D layers.Item Role of Anions in Assembling the Coordination Polymers of Bis–pyridyl–alkanediamides(Wiley, 2016-12-21) Sarkar, MadhushreeFormation of Coordination Polymers (CPs) of an amide based flexible ligand, bis(3-pyridyl)butanediamide, has been found to be directed by the anion of the starting metal salt: a 1D network with rectangular loops was obtained with CuSO4 while a 2D network having two-fold parallel interpenetration was obtained with Cu(ClO4)2. In the 1D network, a π•••π interaction between C=O groups of the amide is present whereas the 2D network shows self-complementary amide-to-amide hydrogen bond. The reaction of the ligand with Cu(C6H5COO)2 results in a 1D chain, where the benzoate units are also coordinated to the Cu(II) centres. The conformational adjustments of the butyl spacer of the ligand in the CPs according to the requirements of the counter anions is observed in the present study. The role of the counter anions (ClO4−, SO42− and C6H5COO−) towards the formation of the CPs was monitored through the competitive reactions, where the ligand was allowed to react with Cu(NO3)2 in the presence of other three counter anions altogether at a time. Further, an understanding on the network stability was gained by studying the counter anion exchange reactions.Item Synthesis of Polymer-Bound 4-Acetoxy-3-phenylbenzaldehyde Derivatives: Applications in Solid-Phase Organic Synthesis(ACS, 2006) Kumar, AnilAminomethyl polystyrene resin was reacted with 4-(5‘-formyl-2‘-hydroxyphenyl)benzoic acid and 4-(5‘-formyl-2‘-hydroxyphenyl)phenyl propionic acid, respectively, in the presence of 1-hydroxybenzotriazole and 1,3-diisopropylcarbodiimide to yield polymer-bound benzaldehydes. The phenolic group in resins was acetylated with acetic anhydride to afford two polymer-bound 4-acetoxybenzaldehydes. The reductive amination of polymer-bound linkers by amines and sodium triacetoxyborohydride, followed by sulfonylation with arylsulfonyl chloride derivatives in the presence of pyridine and the cleavage with TFA/DCM/H2O, produced pure sulfonamides.Item Ionic Liquid-Supported Synthesis of Sulfonamides and Carboxamides(ACS, 2012) Kumar, AnilAn ionic liquid-supported aldehyde was designed and converted to ionic liquid-supported secondary aryl amines through reductive amination. The reaction of ionic liquid-supported aryl amines with sulfonyl chlorides and acid chlorides, respectively, followed by cleavage using trifluoroacetic acid (TFA) afforded sulfonamides and caboxamides. To introduce additional diversity in the synthesis of sulfonamides and caboxamides, ionic liquid-supported iodosubstituted aryl amine was synthesized using the same strategy, and underwent Suzuki coupling reaction, followed by reaction with a methanesulfonyl chloride to generate the corresponding biaryl sulfonamide. The advantages of the protocol over solid-phase synthesis are homogeneous reaction medium, high loading, easy separation of products, and characterization of intermediates.Item NEXT Oxidative Cross-Coupling of sp3- and sp2-Hybridized C–H Bonds: Vanadium-Catalyzed Aminomethylation of Imidazo[1,2-a]pyridines(ACS, 2015-10-19) Kumar, AnilThe vanadium-catalyzed oxidative coupling of substituted 2-arylimidiazo[1,2-a]pyridines to N-methylmorpholine oxide, which acts as both a coupling partner and an oxidant, has been achieved. This reaction was applied to various substituted imidiazo[1,2-a]pyridine and indole substrates, resulting in yields as high as 90%. Mechanistic investigations indicate that the reaction may proceed via a Mannich-type process. This work demonstrates how oxidative aminomethylation can be used as a useful method to introduce tertiary amines into heterocycles, thus providing an alternative method for conventional Mannich-type reactions.