• Volume 117, Issue 3

      May 2005,   pages  207-282

    • Underpotential deposition of metals – Progress and prospects in modelling

      V Sudha M V Sangaranarayanan

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      Underpotential deposition (UPD) of metals is analysed from the perspective of phenomeno-logical and statistical thermodynamic considerations; the parameters influencing the UPD shift have been quantitatively indicated using a general formalism. The manner in which the macroscopic properties pertaining to the depositing ions and solvent dipoles and the nature of the metallic substrate influence the UPD process are highlighted; earlier correlations of the UPD shift with the work function differences are rationalised. Anion-induced phase transitions which manifest as sharp peaks in experimental cyclic voltammograms are discussed using statistical thermodynamic models.

    • Hydrothermal synthesis and structure of [(C4N2H12)3][P2Mo5O23]·H2O and [(C3N2H12)3][P2Mo5O23]·4H2O

      S V Ganesan Srinivasan Natarajan

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      Two new compounds, [(C4N2H12)3][P2Mo5O23]·H2O,I, and [(C3N2H12)3][P2Mo5O23]4H2O,II, have been prepared employing hydrothermal methods in the presence of aliphatic organic amine molecules. Both the compounds possess the same polyoxoanion, pentamolybdatobisphosphate, (P2Mo5O23)6-. The anions consist of a ring of five MoO6 distorted octahedra with four edge connections and one corner connection. The phosphate groups cap the pentamolybdate ring anion on either side. The anion is stabilized by strong hydrogen bonds involving the hydrogen atoms of the amine molecules and the oxygen atoms of the polyoxoanion and water molecules. Crystal data:I, monoclinic, space group = P21/n (no. 14), mol. wt. = 1192.1,a = 9.4180(1),b = 18.1972(3),c = 19.4509(1) å, Β = 103.722(1)‡,V = 3238.37(7) å3, Z = 4;II, triclinic, space group = P1 (no. 2), mol. wt. = 1210.1,a 9.5617(9),b = 13.3393(12),c = 13.7637(12) å, α = 88.735(1), Β = 75.68(1), γ = 87.484(2)‡,V = 1699.2(3) å3.

    • Supramolecular assembly based on a heteropolyanion: Synthesis and crystal structure of Na3(H2O)6[Al(OH)6Mo6O18]·2H2O

      Vaddypally Shivaiah Samar K Das

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      Synthesis and structural characterization of a polyoxometalate compound Na3(H2O)6 [Al(OH)6Mo6O18]-2H2O (1) have been described. Compound1 exhibits three-dimensional network structure in the solid state, which is assembled by Anderson-type heteropolyanions, [Al(OH)6Mo6O18]n3n-, as building blocks sharing sodium cations.1 possesses “sinuous” channels occupied by supramolecular water dimers as guests. Anderson anions, sodium-coordinated water and crystal water are additionally involved in an intricate hydrogen-bonding network in the crystal of1.

    • Ruthenium(II) complexes containing bidentate Schiff bases and triphenylphosphine or triphenylarsine

      P Viswanathamurthi R Karvembu V Tharaneeswaran K Natarajan

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      Reactions of ruthenium(II) complexes [RuHX(CO)(EPh3)2(B)] (X = H or Cl; B = EPh3, pyridine (py) or piperidine (pip); E = P or As) with bidentate Schiff base ligands derived by condensingo- hydroxyacetophenone with aniline,o- orp-methylaniline have been carried out. The products were characterized by analytical, IR, electronic and1H-NMR spectral studies and are formulated as [Ru(X)(CO) (L)(EPh3)(B)] (L = Schiff base anion; X = H or Cl; B = EPh3, py or pip; E = P or As). An octahedral structure has been tentatively proposed for the new complexes. The new complexes were tested for their catalytic activities in the oxidation of benzyl alcohol to benzaldehyde.

    • Synthesis and characterization of mixed ligand complexes of Zn(II) and Co(II) with amino acids: Relevance to zinc binding sites in zinc fingers

      P Rabindra Reddy M Radhika P Manjula

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      Mixed ligand complexes of Zn(II) and Co(II) with cysteine, histidine, cysteinemethylester, and histidinemethylester have been synthesized and characterized by elemental analysis, conductivity, magnetic susceptibility measurements, and infrared,1H NMR, TGA and FAB mass spectra. In these complexes, histidine, and histidinemethylester act as bidentate ligands involving amino and imidazole nitrogens in metal coordination. Similarly, cysteine, and cysteinemethylester also act as bidentate ligands coordinating through thiol sulphur and amino nitrogen. Tetrahedral geometry has been proposed for Zn(II) and Co(II) complexes based on experimental evidence.

    • Syntheses, magnetic and spectral studies on polystyrene supported coordination compounds of bidentate and tetradentate Schiff bases

      D Kumar P K Gupta A Syamal

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      The reaction of aminomethylated polystyrene (PSCH2-NH2) and 2-hydroxyacetanilide in DMF results in the formation of polystyrene-anchored monobasic bidentate Schiff base, PSCH2-LH (I). On the other hand, the reaction of chloromethylated polystyrene (PSCH2-Cl), 3-formylsalicylic acid, ethylenediamine and acetylacetone in DMF in presence of ethyl acetate (EA) and triethylamine (TEA) produces another polystyrene-anchored dibasic tetradentate Schiff base, PSCH2-L′H2 (II). BothI andII react with a number of di-, tri-and hexavalent metal ions like Co, Ni, Cu, Zn and Cd to form polystyreneanchored coordination compounds, and these have been characterized and discussed.

    • Azomesogens with methoxyethyl tail: Synthesis and characterization

      A K Prajapati H M Pandya

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      Two new mesogenic homologous series are synthesized from methoxyethyl 4-(4′-hydroxyphenylazo) benzoate. In series I the phenolic -OH group is alkylated, whereas in series II it is esterified with 4-n-alkoxybenzoyl group. In series I, all the nine members synthesized exhibit only enantiotropic smectic A mesophase. In series II, all the twelve homologues exhibit enantiotropic nematic mesophase. Smectic A mesophase appears from then-decyloxy derivative as a enantiotropic phase and persists till the last n-hexadecyloxy member. The mesomorphic properties of both the series are compared with each other and also with the properties of other structurally related series to evaluate the effect of the methoxyethyl tail on mesomorphism.

    • Β-Sitosterol-3-O-β-D-xylopyranoside from the flowers ofTridax procumbens Linn

      V K Saxena Sosanna Albert

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      Tridax procumbens Linn belongs to the natural order Compositae and is locally known as ‘Ghamra’. It has been found to possess significant medicinal properties. Its leaves are used in bronchial catarrh, dysentery, diarrhoea and to prevent falling of hair. Its flowers and leaves possess antiseptic, insecticidal and parasiticidal properties, and are also used to check haemorrhage from cuts, bruises and wounds.

      The present work deals with the isolation and identification of steroidal saponin, characterized as Β-sitosterol 3-O-β-D-xylopyranoside, which has been isolated from the flowers ofTridax procumbens Linn.

    • Volumetric studies of some amino acids in binary aqueous solutions of MgCl2·6H2O at 288·15, and 308·15 K

      Amalendu Pal Suresh Kumar

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      Densities (ρ) of glycine, L-alanine, and L-valine in aqueous solutions of MgCl2-6H2O (0.1-0.8 mol kg-1) have been measured at 288.15, and 308.15 K. Apparent molar volumes (Vφ), and limiting partial molar volumes (Vφ0) of each amino acid have been calculated. These data were combined with the earlier reportedVφ0 values of glycine, L-alanine, and L-valine in aqueous MgCl2·6H2O solutions at 298.15 K in order to describe the temperature dependence behaviour of partial molar quantities. Group contributions to partial molar volumes have been determined for the amino acids. The trends of transfer volumes (△Vφ0) have been interpreted in terms of solute-cosolute interactions on the basis of a cosphere overlap model. Pair and triplet interaction coefficients have also been calculated from transfer parameters.

    • Viscometric and thermodynamic studies of interactions in ternary solutions containing sucrose and aqueous alkali metal halides at 293·15, 303·15 and 313·15 K

      Reena Gupta Mukhtar Singh

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      Viscosities and densities of sucrose in aqueous alkali metal halide solutions of different concentrations in the temperature range 293.5 to 313.15 K have been measured. Partial molar volumes at infinite dilution (V20) of sucrose determined from apparent molar volume (φv) have been utilized to estimate partial molar volumes of transfer (V2,tr0) for sucrose from water to alkali metal halide solutions. The viscosity data of alkali metal halides in purely aqueous solutions and in the presence of sucrose at different temperatures (293.15, 303.15 and 313.5 K) have been analysed by the Jones-Dole equation. The nature and magnitude of solute-solvent and solute-solute interactions have been discussed in terms of the values of limiting apparent molar volume (φv0), slope (Sv) and coefficients of the Jones-Dole equation. The structure-making and structure-breaking capacities of alkali metal halides in pure aqueous solutions and in the presence of sucrose have been ascertained from temperature dependence ofφv0.

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