Journal of Chemical Sciences

Publications in this journal

• Article: Synthesis and structural characterization of a calcium coordination polymer based on a μ3-bridging tetradentate binding mode of glycine

  S. Natarajan, B.R. Srinivasan, J. K
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  ABSTRACT: A new coordination polymer namely [[Ca6(H–gly)12(H2O)18]Cl12·6H2O]n (1) (H–gly = glycine) has been isolated from the calcium chloride–glycine–water system and structurally characterized. Each Ca(II) in 1 is eight-coordinated and is bonded to eight oxygen atoms three of which are from terminal water molecules and five oxygen atoms from four symmetry related zwitterionic glycine ligands. The H–gly ligands exhibit two different binding modes viz. a monodentate carboxylate ligation and a μ3-tetradentate bridging carboxylate binding mode, which results in the formation of a one-dimensional coordination polymer. In the infinite chain the Ca(II) atoms are organized in a zigzag fashion. A comparative study reveals a rich and diverse structural chemistry of calcium halide–glycine compounds.
  Journal of Chemical Sciences 07/2012; 124(4):781-790.
• Article: “Study of half-sandwich mono and dinuclear complexes of platinum group metals containing pyrazolyl pyridine analogues: Synthesis and spectral characterization”

  Venkateswara Rao Anna, Kota Thirumala Prasad, Peng Wang, Kollipara Mohan Rao
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  ABSTRACT: Abstract: The chelating ligands 3-chloro-6-(3-pyridyl-1-pyrazolyl)pyridazine (pp-Cl) and 3,6-bis(3-pyridyl-1-pyrazolyl)pyridazine (bppp), were prepared by the condensation of pyridylpyrazole and 3,6-dichloropyridazine. The mononuclear complexes [(6-arene)Ru(pp-Cl)Cl]+ {6-arene = C6H6 (1); p-iPrC6H4Me (2)}, [(5-C5Me5)M(pp-Cl)]+ {M = Rh (3); Ir (4)}, [(6-arene)Ru(bppp)Cl]+ {6-arene = C6H6 (5); p-iPrC6H4Me (6)}, [(5-C5Me5)M(bppp)]+ {M =Rh (7); Ir (8)} as well as the binuclear complexes [{(η6-arene)RuCl}2(bppp)]2+ {6 -arene =C6H6 (9); p-iPrC6H4Me (10)} and [{(η5-C5Me5)MCl}2(bppp)]2+ {M = Rh (11); Ir (12)} have been synthesized from 3-chloro-6-(3-pyridyl-1- pyrazolyl)pyridazine (pp-Cl) or 3,6-bis(3-pyridyl-1-pyrazolyl)pyridazine (bppp) and the corresponding dimers [(6-arene)Ru(μ-Cl)Cl]2 and [(η5-C5Me5)M(μ-Cl)Cl]2 respectively. All complexes were isolated as their hexafluorophosphate salts and characterized by IR, NMR, mass spectrometry and UV-visible spectroscopy. The molecular structures of [2]PF6 and [7]PF6 have been established by single crystal X-ray structure analysis.
  Journal of Chemical Sciences 05/2012; 124(2012):565-575.
• Article: Kinetics and mechanism of oxidation of chloramphenicol by 1-chlorobenzotriazole in acidic medium

  R. C. Hiremath, R. V. Jagadeesh, Puttaswamy, S. M. Mayanna
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  ABSTRACT: Chloramphenicol (CAP) is an antibiotic drug having a wide spectrum of activity. The kinetics of oxidation of chloramphenicol by 1-chlorobenzotriazole (CBT) in HClO4 medium over the temperature range 293–323 K has been investigated. The reaction exhibits first-order kinetics with respect to [CBT]o and zero-order with respect to [CAP]o. The fractional-order dependence of rate on [H+] suggests complex formation between CBT and H+. It fails to induce polymerization of acrylonitrile under the experimental conditions employed. Activation parameters are evaluated. The observed solvent isotope effect indicates the absence of hydride transfer during oxidation. Effects of dielectric constant and ionic strength of the medium on the reaction rate have been studied. Oxidation products are identified. A suitable reaction scheme is proposed and an appropriate rate law is deduced to account for the observed kinetic data.
  Journal of Chemical Sciences 05/2012; 117(4):333-336.
• Article: Vapour phase synthesis of salol over solid acids via transesterification

  S. Z. Mohamed Shamshuddin, N. Nagaraju
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  ABSTRACT: The transesterification of methyl salicylate with phenol has been studied in vapour phase over solid acid catalysts such as ZrO2, MoO3 and SO42− or Mo(VI) ions modified zirconia. The catalytic materials were prepared and characterized for their total surface acidity, BET surface area and powder XRD patterns. The effect of mole-ratio of the reactants, catalyst bed temperature, catalyst weight, flowrate of reactants, WHSV and time-on-stream on the conversion (%) of phenol and selectivity (%) of salol has been investigated. A good yield (up to 70%) of salol with 90% selectivity was observed when the reactions were carried out at a catalyst bed temperature of 200°C and flow-rate of 10 mL/h in presence of Mo(VI)/ZrO2 as catalyst. The results have been interpreted based on the variation of acidic properties and powder XRD phases of zirconia on incorporation of SO42− or Mo(VI) ions. The effect of poisoning of acid sites of SO42− or Mo(VI) ions modified zirconia on total surface acidity, powder XRD phases and catalytic activity was also studied. Possible reaction mechanisms for the formation of salol and diphenyl ether over acid sites are proposed. KeywordsSalol-solid acids-diphenyl ether-zirconia-vapour phase transesterification
  Journal of Chemical Sciences 05/2012; 122(2):193-201.
• Article: Unusual products in the reactions of phosphorus(III) compounds with N=N, C≡C or conjugated double-bonded systems

  K. C. Kumara Swamy, E. Balaraman, M. Phani Pavan, N. N. Bhuvan Kumar, K. Praveen Kumar, N. Satish Kumar
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  ABSTRACT: The diversity of products in the reaction of diethyl azodicarboxylate (DEAD)/diisopropyl azodicarboxylate (DIAD) and activated acetylenes with PIII compounds bearing oxygen or nitrogen substituents is discussed. New findings that are useful in understanding the nature of intermediates involved in the Mitsunobu reaction are highlighted. X-ray structures of two new compounds (2-t-Bu-4-MeC6H3O)P (μ-N-t-Bu)2P+[(NH-t-Bu)N[(CO2]-i-Pr)(HNCO2-i-Pr)]](Cl-)(2-t-Bu-4-MeC6H3OH)(23)and [CH2(6-t-Bu-4-Me-C6H2O)2P(O)C(CO2Me)C-(CO2Me)CClNC(O)Cl] (33) are also reported. The structure of23 is close to one of the intermediates proposed in the Mitsunobu reaction.
  Journal of Chemical Sciences 05/2012; 118(6):495-501.
• Article: Supramolecular network formed through O-H⋯O and π-π stacking interactions: Hydrothermal syntheses and crystal structures of M(H2O)6](optp)2 (M = Mg, Ni, Zn, and optp = 1-oxopyridinium-2-thiopropionate)

  Murugan Indrani, Ramasamy Ramasubramanian, Frank R. Fronczek, Dario Braga, N. Y. Vasanthacharya, Sudalaiandi Kumaresan
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  ABSTRACT: A novel class of complexes of the type [M(H2O)6](optp)2 (where M = Mg, Ni, Zn, and optp = 1-oxopyridinium-2-thiopropionate) were prepared hydrothermally from metal acetates and 1-oxopyridinium-2-thiopropionic acid (Hoptp), and structurally characterized by X-ray diffraction. Complexes [Mg(H2O)6](optp)2 (1), [Ni(H2O)6](optp)2 (2) and [Zn(H2O)6](optp)2 (3) have isomorphic structures, consisting of one [M(H2O)6]2+ cation and two anions of Hoptp, which are linked through hydrogen bonding to form extended networks. In each case, the metal cation sits on a crystallographic centre of inversion and binds to six water molecules. The organic anions form a one-dimensional chain with the hexaaquametal(II) moieties via hydrogen bonds.
  Journal of Chemical Sciences 05/2012; 121(4):413-420.
• Article: Modern Trends in Inorganic Chemistry (MTIC-XIII)

  S VASUDEVAN, G U KULKARNI
  Journal of Chemical Sciences 04/2012; 123(2):95-95.
• Article: Kinetics of oxidation of acidic amino acids by sodium N-bromobenzenesulphonamide in acid medium: A mechanistic approach

  Puttaswamy, Nirmala Vaz
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  ABSTRACT: Kinetics of oxidation of acidic amino acids (glutamic acid (Glu) and aspartic acid (Asp)) by sodium N-bromobenzenesulphonamide (bromamine-B or BAB) has been carried out in aqueous HClO4 medium at 30°C. The rate shows first-order dependence each on [BAB]o and [amino acid]o and inverse first-order on [H+]. At [H+] > 0·60 mol dm−3, the rate levelled off indicating zero-order dependence on [H+] and, under these conditions, the rate has fractional order dependence on [amino acid]. Succinic and malonic acids have been identified as the products. Variation of ionic strength and addition of the reaction product benzenesulphonamide or halide ions had no significant effect on the reaction rate. There is positive effect of dielectric constant of the solvent. Proton inventory studies in H2O-D2O mixtures showed the involvement of a single exchangeable proton of the OH− ion in the transition state. Kinetic investigations have revealed that the order of reactivity is Asp > Glu. The rate laws proposed and derived in agreement with experimental results are discussed.
  Journal of Chemical Sciences 04/2012; 113(4):325-332.
• Article: Two different zinc(II)-aqua complexes held up by a metal-oxide based support: Synthesis, crystal structure and catalytic activity of [HMTAH]2[{Zn(H2O)5}{Zn(H2O)4}{Mo7O24}]·2H2O (HMTAH = protonated hexamethylenetetramine)

  T. Arumuganathan, A. Srinivasarao, T. Vijay Kumar, Samar K. Das
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  ABSTRACT: An inorganic-organic hybrid material, [HMTAH]2[{Zn(H2O)5}{Zn(H2O)4}{Mo7O24}]·2H2O (1) (where HMTAH = protonated hxamethylenetetramine) has been synthesized and structurally characterized. The compound 1 crystallizes in a monoclinic space group C2/c. The crystal data of 1: a = 43.12(3), b = 12.399(10), c = 16.285(13), β = 111.131(11), Z = 8. Its crystal structure shows that two different Zn(II)-aqua complexes, [Zn(H2O)5]2+ and [Zn(H2O)4]2+ are covalently coordinated to a heptamolybdate anion [Mo7O24]6− resulting in an anionic species of polyoxometalate supported zinc-aqua complexes, [{Zn(H2O)5}{Zn(H2O)4}{Mo7O24}]2−, that is stabilized with two protonated hexamethylenetetramine cations in the title compound 1. In the crystal structure, both lattice water molecules are found to interact with the heptamolybdate cluster anion and the protonated hexamethylenetetramine cation resulting in an intricate three-dimensional hydrogen bonding network. Interestingly, compound 1 exhibits catalytic activity towards oxidation of some primary alcohols.
  Journal of Chemical Sciences 04/2012; 120(1):95-103.
• Article: Synthesis, magnetic and spectral studies on polystyrene-anchored coordination complexes of bi-, tri-, tetra- and hexavalent metal ions with unsymmetrical dibasic tetradentate ONNO donor Schiff base derived from 3-formylsalicylic acid, ethylenediamine and 2-benzoylacetanilide

  Dinesh Kumar, Arun Syamal, Jaipal, Lalit Kumar Sharma
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  ABSTRACT: Polystyrene-anchored Cu(II), Zn(II), Cd(II), Ni(II), Mn(II), MoO2(II), UO2(II), Fe(III) and Zr(IV), complexes of the unsymmetrical dibasic tetradentate ONNO donor Schiff base derived from the condensation of chloromethylated polystyrene, 3-formylsalicylic acid, ethylenediamine and 2-benzoylacetanilide (PS-LH2) has been synthesized. The polystyrene anchored complexes have the formulae: PS-LM (where M = Cu, Zn, Cd, Ni, MoO2, UO2), PS-LFeCl·DMF, PS-LMn·2DMF and PS-LZr(OH)2·DMF. The polystyrene-anchored coordination compounds have been characterized by elemental analysis, IR, reflectance, ESR and magnetic susceptibility measurements. The per cent reaction conversion of polystyrene anchored Schiff base to polystyrene supported coordination compounds lies between 28·98 and 85·9. The coordinated dimethylformamide is completely lost on heating the complexes. The shifts of the ν(C=N)(azomethine) and ν(C-O)(phenolic) stretches have been monitored in order to find out the donor sites of the ligands. The Cu(II) complex is paramagnetic with square planar structure; the Ni(II) complex is diamagnetic with square planar structure; the Zn(II) and Cd(II) complexes are diamagnetic and have tetrahedral structure; the Mn(II) and Fe(III) complexes are paramagnetic and have octahedral structure; the MoO2(II) and UO2(II) complexes are diamagnetic and have octahedral structure and the Zr(IV) complexes are diamagnetic and have pentagonal bipyramidal structure.
  Journal of Chemical Sciences 04/2012; 121(1):57-64.
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  Article: Fluorescence resonance energy transfer (FRET) in chemistry and biology: Non-Förster distance dependence of the FRET rate

  Sangeeta Saini, Harjinder Singh, Biman Bagchi
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  ABSTRACT: Fluorescence resonance energy transfer (FRET) is a popular tool to study equilibrium and dynamical properties of polymers and biopolymers in condensed phases and is now widely used in conjunction with single molecule spectroscopy. In the data analysis, one usually employs the Förster expression which predicts (l/R 6) distance dependence of the energy transfer rate. However, critical analysis shows that this expression can be of rather limited validity in many cases. We demonstrate this by explicitly considering a donor-acceptor system, polyfluorene (PF6)-tetraphenylporphyrin (TPP), where the size of both donor and acceptor is comparable to the distance separating them. In such cases, one may expect much weaker distance (as l/R 2 or even weaker) dependence. We have also considered the case of energy transfer from a dye to a nanoparticle. Here we find l/R 4 distance dependence at large separations, completely different from Förster. We also discuss recent application of FRET to study polymer conformational dynamics.
  Journal of Chemical Sciences 04/2012; 118(1):23-35.
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  Article: Ruthenium(II)- bipyridyl with extended π-system: Improved thermo-stable sensitizer for efficient and long-term durable dye sensitized solar cells

  M CHANDRASEKHARAM, G RAJKUMAR, CH SRINIVASA RAO, T SURESH, P Y REDDY, Y SOUJANYA
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  ABSTRACT: A new extended thermo-stable high molar extinction coefficient bipyridyl ruthenium(II) complex “cis-Ru(4,4’-bis(3,5-di-tert-butylphenyl)-2,2’-bipyridine)(Ln)(NCS)2 H101”, where Ln = 4,4’-dicarboxylic acid-2,2’-bipyridine; was synthesized and characterized by 1H-NMR, FT-IR and ESI-MASS spectroscopes. The H101 sensitized solar cell constructed with an active area of 0.54 cm2 in combination with an ionic liquid electrolyte exhibited broader photocurrent action spectrum with solar-to-electric energy conversion efficiency (η) of 5.89 (JSC =\textbf{\textit{J}}_{\rm SC} = 12.14 mA/cm2, VOC =\textbf{\textit{V}}_{\rm OC} = 690V, fill factor = 0.699) under Air Mass (AM) 1.5 sunlight, while the reference ‘cis-Ru(4,4’-dinonyl-2,2’-bipyridine)(Ln)(NCS)2’, Z907 sensitized solar cell exhibited η-value of 5.17% (JSC =\textbf{\textit{J}}_{\rm SC} = 11.93 mA/cm2, VOC =\textbf{\textit{V}}_{\rm OC} = 650V, fill factor = 0.666). TGA analysis of H101 showed extended thermal-stability and under continuous light exposure and aging at 55°C, the DSSC retained 85% of its initial η-value, while under comparable conditions Z907 sensitized solar cell retained 88%. As compared to 4,4’-dinonyl-2,2’-bipyridine in Z907, the new ancillary bipyridyl ligand ‘4,4’-bis(3,5-di-tert-butylphenyl)-2,2’-bipyridine’ in H101 shifts the absorption bands remarkably towards blue. The Density Functional Theory (DFT) and Time-Dependent DFT excited state calculations of the new sensitizer show that the first three HOMOs have t2g character with sizeable mixing from the NCS ligands with π-bonding orbitals of 4,4’-bis(3,5-di-tert-butylphenyl)-2,2’-bipyridine. The LUMO is a π*-orbital localized on the 4,4-dicarboxylic acid-2,2’-bipyridine and higher un-occupied frontier orbitals have π*-combinations with 4,4’-bis(3,5-di-tert-butylphenyl)-2,2’-bipyridine. Graphical AbstractA new extended thermo-stable high molar extinction coefficient bipyridyl ruthenium(II) complex “cis-Ru(4,4’-bis(3,5-di-tert-butylphenyl)-2,2’-bipyridine)(Ln)(NCS)2 H101” (where Ln = 4,4’-dicarboxylic acid-2,2’-bipyridine) was synthesized. The test cell DSSC constructed from H101 sensitizer with an active area of 0.54 cm2 in combination with an ionic liquid electrolyte exhibited broader photocurrent action spectrum with solar-to-electric energy conversion efficiency (η) of 5.89 (J SC = 12.14 mA/cm2, V OC = 690 V, fill factor = 0.699) under Air Mass (AM) 1.5 sunlight. KeywordsDye sensitized solar cells–extended π-system–thermo-stable–Polypyridyl Ru(II)-sensitizers
  Journal of Chemical Sciences 04/2012;
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  Article: Preparation of amine coated silver nanoparticles using triethylenetetramine

  L. Ramajo, R. Parra, M. Reboredo, M. Castro
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  ABSTRACT: This article presents a simple method towards the preparation of functionalized silver nanoparticles in a continuous medium. Silver nanoparticles were obtained through AgNO3 chemical reduction in ethanol and triethylenetetramine was used to stabilize and functionalize the metal. The product was characterized with X-ray diffraction (XRD), Fourier-transformed infrared spectroscopy (FTIR), UV-visible spectroscopy, thermal gravimetric analysis (TGA) and transmission electron microscopy (TEM). Monocrystalline silver particles with cubic structure and an average size of 20 nm were obtained. The results reveal that it is possible to synthesize Ag nanoparticles functionalized with amine groups and that particle size is influenced by the processing route.
  Journal of Chemical Sciences 04/2012; 121(1):83-87.
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  Article: Reactive chemical dynamics through conical intersections

  S. Ghosal, B. Jayachander Rao, S. Mahapatra
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  ABSTRACT: Reaction dynamics of prototypical, D + H2 and Cl (2P) + H2, chemical reactions occurring through the conical intersections of the respective coupled multi-sheeted potential energy surfaces is examined here. In addition to the electronic coupling, nonadiabatic effects due to relativistic spin-orbit coupling are also considered for the latter reaction. A time-dependent wave packet propagation approach is undertaken and the quantum dynamical observables viz., energy resolved reaction probabilities, integral reaction cross-sections and thermal rate constants are reported.
  Journal of Chemical Sciences 04/2012; 119(5):401-407.