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.

Head-group size or hydrophilicity of surfactants: the major regulator of lipase activity in cationic water-in-oil microemulsions

Abstract: To determine the crucial role of surfactant head-group size in micellar enzymology, the activity of Chromobacterium Viscosum (CV) lipase was estimated in cationic water-in-oil (w/o) microemulsions of three different series of surfactants with varied head-group size and hydrophilicity. The different series were prepared by subsequent replacement of three methyl groups of cetyltrimethylammonium bromide (CTAB) with hydroxyethyl (1-3, series I), methoxyethyl (4-6, series II), and n-propyl (7-9, series III) groups. The hydrophilicity at the polar head was gradually reduced from series I to series III. Interestingly, the lipase activity was found to be markedly higher for series II surfactants relative to their more hydrophilic analogues in series I. Moreover, the activity remained almost comparable for complementary analogues of both series I and III, though the hydrophilicity was drastically different. Noticeably, the head-group area per surfactant is almost similar for comparable surfactants of both series I and III, but distinctly higher in case of series II surfactants. Thus the lipase activity was largely regulated by the surfactant head-group size, which plays the dominant role over the hydrophilicity. The increase in head-group size presumably allows the enzyme to attain a flexible conformation as well as increase in the local concentration of enzyme and substrate, leading to the higher efficiency of lipase. The lipase showed its best activity in the microemulsion of 6 probably because of its highest head-group size. Furthermore, the observed activity in 6 is 2-3-fold and 8-fold higher than sodium bis(2-ethyl-1-hexyl)sulfosuccinate (AOT) and CTAB-based microemulsions, respectively, and in fact highest ever in any w/o microemulsions.

Water soluble polythiophenes: preparation and applications

Abstract: This review describes the synthesis of different water soluble polythiophenes and their versatile applications Solubility in water is essential for developing sensors for different bio-molecules and polythiophene derivatives are excellent candidates due to their important optoelectronic properties A pristine polythiophene chain is hydrophobic and it exhibits aqueous solubility after attachment/grafting of ionic pendent groups or hydrophilic polymer chains on its backbone A concise account of the different synthetic procedures of preparing water soluble polythiophene is described and all the specific techniques relevant to the synthesis of water soluble polythiophene using cationic, anionic pendent groups and grafting of hydrophilic polymers are discussed Different grafting processes eg “grafting from” and “grafting to” techniques using click chemistry and atom transfer radical polymerization (ATRP) are described in detail Detections of different bio-molecules such as DNA, RNA, polypeptides, polysaccharides, ATP, UDP and ADP from the excellent opto-electronic properties of aqueous polythiophenes are discussed The reports on fluorescence based specific sensing of metal ions, and nitro-aromatics using water soluble polythiophenes are also embodied with an up-to-date description of the optoelectronic device applications such as logic gates, molecular thermometers, photovoltaic cells etc Finally, a summary and outlook is presented discussing the future scope of research on this important subject

Hydrogenation of azides over copper nanoparticle surface using ammonium formate in water.

Abstract: Aryl azides undergo clean reduction by copper nanoparticles and ammonium formate in water. The surface hydrogen on copper nanoparticles is considered to be the active reducing species. A variety of functionalized aryl azides and aryl sulfonyl azides are reduced by this procedure to the corresponding amines with excellent chemoselectivity in high yields.

Structural and Magnetic Properties of Two Carboxylato‐Bridged Manganese(II) Complexes with N‐Donor Coligands

Abstract: Two polymeric MnII complexes, [(m-phth)(Mn)(bpp)2]·0.5H2O (1) and [(mal)2(Mn)2(H2O)2(hmt)] (2) [mal = malonate; hmt = hexamethylenetetramine; bpp = 1,3-bis(4-pyridyl)propane; m-phth = 1,3-benzenedicarboxylate] have been synthesized. Complex 1 consists of 1D chains (with monocoordinated bpp) that are held together to form a 2D extended network of hydrogen bonding between lattice water molecules and uncoordinated bpp donors. Variable-temperature magnetic susceptibility data of the complex have been fitted applying the formula used for dinuclear complexes of MnII ions, considering interdimer interactions (J′). The following parameters were obtained from the best fit: J = −0.88 ± 0.02 cm−1, J′ = −0.1 cm−1 and g = 1.99 ± 0.01. The agreement factor R = Σ(χmTobsd. − χmTcalcd.)2/Σ(χmTcalcd.)2 is 1.110−5. Complex 2 is a 3D polymeric network where syn/anti-bridging malonate ligands and MnII centers are assembled in the form of [Mn(H2O)(mal)]n layers, which are further connected by hexamethylenetetramine. The magnetic data have been fitted considering the complex as a pseudo-two-dimensional sheet of MnII cations and malonate anions since the coupling through the hexamethylenetetramine ligand is almost zero. We have followed two approaches for fitting the data, (a) through the expansion series of Line’s equation for the S = 5/2 antiferromagnetic quadratic layer and (b) by using the equation based on an infinite 2D square lattice composed of isotropically coupled classical spin S = 5/2. Both approaches result in excellent theoretical fits and similar J values of −0.24 cm−1 and −0.21 cm−1 for the Line’s and Curely equations, respectively. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Cobalt(II)-(dpyo)-dicarboxylate networks: unique H-bonded assembly and rare bridging mode of dpyo in one of them [dpyo = 4,4'-dipyridyl N,N'-dioxide].

Abstract: Polymeric networks, {[Co(dpyo)(ox)]}n (1), {[Co(dpyo)(fum)(H2O)2]}n (2) and {[Co(dpyo)(tp)(H2O)2]·[Co(H2O)6]·(tp)·(H2O)}n (3) [ox = oxalate dianion, fum = fumarate dianion, tp = terephthalate dianion and dpyo = 4,4′-dipyridyl N,N′-dioxide] have been synthesized and characterized by single crystal X-ray diffraction analyses. The structural determination reveals 1 and 2 are covalent bonded 2D networks of 4,4 topology and of these, complex 2 undergoes a H-bonding scheme resulting in a 3D supramolecular architecture. Complex 3 is a 1D coordination polymer built up by almost collinear hexacoordinated Co(II), doubly bridged by a tp carboxylate group and a dpyo oxygen, which in combination with lattice [Co(H2O)6]2+, tp and water molecules shows an unprecedented 3D supramolecular network through H-bonding. In the polymer the dpyo shows novel µ-4,4 bridging mode towards the cobalt ion. Low temperature magnetic interaction reveals antiferromagnetic coupling in all of the complexes.