• Volume 116, Issue 5

      September 2004,   pages  245-300

    • Synthesis, characterization and emission properties of quinolin-8-olato chelated ruthenium organometallics

      Bikash Kumar Panda

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      The reaction of Ru(RL1)(PPh3)2(CO)Cl,1, with quinolin-8-ol (HQ) has afforded complexes of the type [Ru(RL2)(PPh3)2(CO)(Q)],3, in excellent yield (RL1 is C6H2O-2-CHNHC6H4R(p)-3-Me-5, RL2 is C6H2OH-2-CHNC6H4R(p)-3-Me-5 and R is Me, OMe, Cl). In this process, quinolin-8-olato (Q) undergoes five-membered chelation, the iminium-phenolato function tautomerizing to the imine-phenol function. In dichloromethane solution,3 displays a quasireversible3+/3 couple near 0·50 V vs SCE (3+ is the ruthenium (III) analogue of3). Coulometrically generated solutions of3+ display a strong absorption near 395 nm associated with a shoulder near 475 nm and rhombic EPR spectra withg values near 2·55, 2·13, 1·89. Solutions of3 absorb near 415 nm and emit near 510 nm at 298 K and 585 nm at 77 K. The fluorescence is believed to originate from the3MLCT state

    • Does an all-sulphur analogue of heptamolybdate exist?

      Bikshandarkoil R Srinivasan

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      The complexes [MoX4]2− (M = Mo; X = O or S) exist as the monomeric tetrahedral species in aqueous alkaline solutions. Acidification of tetraoxomolybdate results in the condensation of the tetrahedral units via a series of polyoxomolybdates leading to the ultimate formation of the trioxide MoO3. Heptamolybdate [Mo7O24]6− is the first major polyanion of the acidification reaction. In contrast, acidification of tetrathiomolybdates leads to the formation of amorphous molybdenum trisulphide via a dinuclear Mo(V) complex. The formation of the dinuclear Mo(V) complex precludes the formation of any higher nuclearity Mo(VI)-S complexes in aqueous solution. Thus it is shown that the all-sulphur analogue of heptamolybdate [M07S24]6− does not exist in alkaline medium and also cannot be isolated from aqueous acidic medium

    • Deprotection of oximes using urea nitrate under microwave irradiation

      P T Perumal M Anniyappan D Muralidharan

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      A new mild and efficient method for the cleavage of oximes to carbonyl compounds using readily available urea nitrate in acetonitrile-water (95:5), under microwave irradiation within 2 min, in good yields is reported

    • Synthesis of spiro[indolo-1,5-benzodiazepines] from 3-acetyl coumarins for use as possible antianxiety agents

      Raviraj A Kusanur Manjunath Ghate Manohar V Kulkarni

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      3-Acetyl coumarins (1) when allowed react with isatin (2) gave corresponding 3-(3′-hydroxy-2′-oxo indolo) acetyl coumarins (3), which on dehydration afforded the correspondingα,β-unsaturated ketones (4). Cyclocondensation of (4) with substitutedo-phenylene diamines resulted in novel 3-coumarinyl spiro[indolo-1,5-benzodiazepines] (5). Structures of all the compounds have been established on the basis of their IR, NMR and mass spectral data and have been screened for their antimicrobial activity and antianxiety activity in mice

    • A theoretical study of porphyrin isomers and their core-modified analogues:cis-trans isomerism, tautomerism and relative stabilities

      M Punnagai Saju Joseph G Narahari Sastry

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      Semiempirical (AM1 and PM3) and density functional theory (DFT) calculations were performed on about 50 porphyrin isomers with 25 each of 1,2 (syn) and 1,3 (anti) tautomeric forms. The corresponding oxa-and thia-core-modified analogues were also computed. The variations of relative energies and stabilities of the core-modified analogues were compared with parent porphyrin1 and the corresponding oxa-and thia-analogues. The trends in relative energies are not significantly changed while going from parent system to oxa-and thia-core-modified porphyrins in case of bothsyn andanti tautomers. Isomers of types [2·2·0·0], [3·0·1·0], [3·1·0·0], and [4·0·0·0] are destabilized due to the absence of methine bridge, which results in angle strain for tetrapyrroles. Isomers having [2·1·1·0], [2·1·0·1], [2·0·2·0] and [2·2·0·0] connectivity, the Z isomers, are more stable compared to the correspondingE isomers in bothsyn andanti forms of parent and core-modified analogues.

    • Diagonalization of a real-symmetric Hamiltonian by genetic algorithm: A recipe based on minimization of Rayleigh quotient

      Subhajit Nandy Pinaki Chaudhury S P Bhattacharyya

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      A genetic algorithm-based recipe involving minimization of the Rayleigh quotient is proposed for the sequential extraction of eigenvalues and eigenvectors of a real symmetric matrix with and without basis optimization. Important features of the method are analysed, and possible directions of development suggested

    • Phase transfer of platinum nanoparticles from aqueous to organic solutions using fatty amine molecules

      Ashavani Kumar Hrushikesh M Joshi Anandrao B Mandale Rajendra Srivastava Suguna D Adyanthaya Renu Pasricha Murali Sastry

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      In this report we demonstrate a simple process based on amine chemistry for the phase transfer of platinum nanoparticles from an aqueous to an organic solution. The phase transfer was accomplished by vigorous shaking of a biphasic mixture of platinum nanoparticles synthesised in an aqueous medium and octadecylamine (ODA) in hexane. During shaking of the biphasic mixture, the aqueous platinum nanoparticles complex via either coordination bond formation or weak covalent interaction with the ODA molecules present in the organic phase. This process renders the nanoparticles sufficiently hydrophobic and dispersible in the organic phase. The ODA-stabilised platinum nanoparticles could be separated out from hexane in the form of a powder that is readily redispersible in weakly polar and non-polar organic solvents. The ODA-capped platinum nanoparticles show high catalytic activity in hydrogenation reactions and this is demonstrated in the efficient conversion of styrene to ethyl benzene. The nature of binding of the ODA molecules to the platinum nanoparticles surface was characterised by thermogravimetry, transmission electron microscopy (TEM), X-ray photoemission spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR)

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