Indian Association for the Cultivation of Science

About: Indian Association for the Cultivation of Science is a education organization based out in Kolkata, India. It is known for research contribution in the topics: Catalysis & Excited state. The organization has 3867 authors who have published 10457 publications receiving 220098 citations.

Palladium nanoparticle-catalyzed C-N bond formation. A highly regio- and stereoselective allylic amination by allyl acetates.

Abstract: Palladium nanoparticles, generated in situ from the reaction of palladium(II) chloride, have been demonstrated to be an efficient catalyst for C−N bond formation. A variety of aliphatic and aromatic amines have been allylated by substituted and unsubstituted allyl acetates in high yields by using palladium nanoparticles in the presence of a base without any ligand. The allylations are highly regio- and stereoselective.

Self-assembled TiO2 nanospheres by using a biopolymer as a template and its optoelectronic application.

Abstract: Self-assembled TiO2 nanoparticulate materials with well-defined spherical morphologies were synthesized by using a biopolymer sodium alginate as a template under different synthesis conditions. Powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) techniques were used to characterize the TiO2 nanoparticles. N2 sorption analysis revealed the moderately good surface area (124.0 m2 g–1) and pore volume (0.44 cm3 g–1) of these TiO2 nanoparticles. The biopolymer templating pathway leads to good-quality self-assembled TiO2 nanoparticles with dimensions of ca. 10–12 nm within the synthesis temperature range of 0–60 °C. These porous TiO2 nanomaterials showed high photogenerated current in the presence of a dye (Rose Bengal), used as a sensitizer for several photo on/off cycles.

Synthesis, structural analysis, and magnetic behaviour of three fumarate bridged coordination polymers: five-fold interpenetrated diamond-like net of NiII, sheets of NiII and CoII

Abstract: The hydrothermal reactions of Ni(NO3)2·6H2O, disodium fumarate (fum) and 1,2-bis(4-pyridyl)ethane (bpe)/1,3-bis(4-pyridyl)propane (bpp) in aqueous–methanol medium yield one 3-D and one 2-D metal–organic hybrid material, [Ni(fum)(bpe)] (1) and [Ni(fum)(bpp)(H2O)] (2), respectively. Complex 1 possesses a novel unprecedented structure, the first example of an “unusual mode” of a five-fold distorted interpenetrated network with metal–ligand linkages where the four six-membered windows in each adamantane-type cage are different. The structural characterization of complex 2 evidences a buckled sheet where nickel ions are in a distorted octahedral geometry, with two carboxylic groups, one acting as a bis-chelate, the other as a bis-monodentate ligand. The metal ion completes the coordination sphere through one water molecule and two bpp nitrogens in cis position. Variable-temperature magnetic measurements of complexes 1 and 2 reveal the existence of very weak antiferromagnetic intramolecular interactions and/or the presence of single-ion zero field splitting (D) of isolated NiII ions in both the compounds. Experimentally, both the J parameters are close, comparable and very small. Considering zero-field splitting of NiII, the calculated D values are in agreement with values reported in the literature for NiII ions. Complex 3, [{Co(phen)}2(fum)2] (phen = 1,10-phenanthroline) is obtained by diffusing methanolic solution of 1,10-phenanthroline on an aqueous layer of disodium fumarate and Co(NO3)2·6H2O. It consists of dimeric CoII(phen) units, doubly bridged by carboxylate groups in a distorted syn–syn fashion. These fumarate anions act as bis-chelates to form corrugated sheets. The 2D layer has a (4,4) topology, with the nodes represented by the centres of the dimers. The magnetic data were fitted ignoring the very weak coupling through the fumarate pathway and using a dimer model.

Slow solvation dynamics at the active site of an enzyme: implications for catalysis.

Abstract: Solvation dynamics at the active site of an enzyme, glutaminyl-tRNA synthetase (GlnRS), was studied using a fluorescence probe, acrylodan, site-specifically attached at cysteine residue C229, near the active site. The picosecond time-dependent fluorescence Stokes shift indicates slow solvation dynamics at the active site of the enzyme, in the absence of any substrate. The solvation dynamics becomes still slower when the substrate (glutamine or tRNAGln) binds to the enzyme. A mutant Y211H-GlnRS was constructed in which the glutamine binding site is disrupted. The mutant Y211H-GlnRS labeled at C229 with acrylodan exhibited significantly different solvent relaxation, thus demonstrating that the slow dynamics is indeed associated with the active site. Implications for catalysis and specificity have been discussed.