BITS Faculty Publications

Permanent URI for this communityhttp://localhost:4000/handle/123456789/1867

Browse

End date: 1999Subject: search.filters.subject.Chemistry

Search Results

Now showing 1 - 10 of 34
  • No Thumbnail Available
    Item
    Magnetic resonance lineshapes in powdered and amorphous systems
    (IAS, 1986-04) Sivasubramanian, S.C.
    A survey is made of the theory and applications ofEPR andNMR absorption lineshapes observed in powdered and amorphous materials. The ‘spin Hamiltonian’ and ‘resonance condition’ formalisms are reviewed, andepr andnmr lineshapes are discussed which typify the singularity characteristics in powdered materials. In the amorphous or ‘glassy’ state, the measurable spin resonance parameters often have to be viewed as being ‘randomly distributed’ according to a probability density function. Several recent probability-theory based approaches to lineshape computation for modelling the amorphous state are discussed.
  • No Thumbnail Available
    Item
    X-ray diffraction, electron paramagnetic resonance, and electron spin echo modulation studies of the lead oxide-lead chloride-cupric chloride ternary glass system
    (ACS, 1991-08-01) Sivasubramanian, S.C.
    X-ray diffraction, EPR, and ESEM studies are reported for a novel ternary glass 43PbO-56PbCl2-1 CuCl2. The X-ray PDF data lead to a structural model in which octahedral building units of Cu04Cl2 are predominant. EPR spectra of the glass at X and Q bands have been fitted, by line shape simulation, to the distributed spin Hamiltonian parameters g^rnean) = 2.34, = 0.03, gx(mean) = 2.06, ± = 0.008, p = 0.95, /4,(mean) = 131.1 X 10"4 cm"1, and /4x(mean) = 5.8 X 10"4 cm"1. These data suggest a distribution of bonding geometries for Cu2+ in the glass structure, with the above-mentioned elongated octahedral Cu04Cl2 dominating. ESEM results suggest that Cu2+ may be surrounded by four Pb2+ in the second coordination shell at a distance of 3.8 Á
  • No Thumbnail Available
    Item
    X-ray diffraction, electron paramagnetic resonance, and electron spin echo modulation studies of the lead oxide-lead chloride-cupric chloride ternary glass system
    (ACS, 1991-08-01) Sivasubramanian, S.C.
    X-ray diffraction, EPR, and ESEM studies are reported for a novel ternary glass 43PbO-56PbCl2-1 CuCl2. The X-ray PDF data lead to a structural model in which octahedral building units of Cu04Cl2 are predominant. EPR spectra of the glass at X and Q bands have been fitted, by line shape simulation, to the distributed spin Hamiltonian parameters g^rnean) = 2.34, = 0.03, gx(mean) = 2.06, ± = 0.008, p = 0.95, /4,(mean) = 131.1 X 10"4 cm"1, and /4x(mean) = 5.8 X 10"4 cm"1. These data suggest a distribution of bonding geometries for Cu2+ in the glass structure, with the above-mentioned elongated octahedral Cu04Cl2 dominating. ESEM results suggest that Cu2+ may be surrounded by four Pb2+ in the second coordination shell at a distance of 3.8 Á.
  • No Thumbnail Available
    Item
    Syntheses and characterization of N,N′-dipropyl/diisopropylethane-1,2-diamine complexes of nickel(II) nitrate: Thermal studies and X-ray single crystal structure analysis of cis-nitratobis (N,N′-dipropylethane-1,2-diamine)nickel(II) nitrate
    (Elsiever, 1998) Laskar, Inamur Rahaman
    The blue complex cis-[Ni(dipren)2(NO3)](NO3) 1 and the greenish blue cis-[Ni(dipren)2(H2O2](NO3)2 · 2H2O2 (dpren/dpren = dipropyl/diisopropylethane-1,2-diamine) have been synthesized. Complex 2 upon heating loses four water molecules in a single step and undergoes melting accompanied with colour change, greenish blue to deep green, 2a. Configuration of the complexes 1,2 and 2a have been proposed to be cis-octahedral on the basis of magnetic, IR and electronic spectroscopic studies and confirmed in case of complex 1 by X-ray single crystal structure analysis. The role of steric factor of the alkyl groups on the selectivity of coordinating mode of nitrate ion is studied.
  • No Thumbnail Available
    Item
    Synthesis and Single-Crystal Structure of an Unusual Heptacoordinate Cadmium(II) Complex, [Cd(medien)(NO3)2] (medien = bis(2-aminoethyl)methylamine).
    (ACTA, 1998) Laskar, Inamur Rahaman
    Molecular geometry and coordination number play the key role in exploring the chemistry of a coordination compound.
  • No Thumbnail Available
    Item
    Synthesis, Characterization and Thermal Studies of Bis(2-aminoethyl)methylamine(medien) Complexes of Cadmium(II). Single Crystal Structure of Cd(medien)I2.
    (ACTA, 1998) Laskar, Inamur Rahaman
    The synthesis and characterization of bis complexes of bis(2-aminoethyl) amine (dien) with transition and non transition metals are of interest as these complexes can potentially exist in three isomeric forms
  • No Thumbnail Available
    Item
    First structural characterisation of nitro–nitrito linkage isomers of nickel(II): synthesis and single crystal structures of [NiL2(NO2)2] and [NiL2(ONO)2] [L = 1-(2-aminoethyl)piperidine]
    (RSC, 1998) Laskar, Inamur Rahaman
    The linkage isomers trans-bis[1-(2-aminoethyl)piperidine]dinitronickel(II) (brown) 1 and trans-bis[1-(2-aminoethyl)piperidine]dinitritonickel(II) (blue) 2 have been synthesized and characterised by X-ray single crystal structure analysis.
  • No Thumbnail Available
    Item
    Synthesis of s-fac/mer bis(N2-methyldiethylenetriamine, L) nickel(II): X-ray single crystal structures of s-fac[NiL2](NO3)2 and mer[NiL2](CF3CO2)2
    (Springer, 1999-06) Laskar, Inamur Rahaman
    [NiL2](NO3)2 (1) and [NiL2](CF3CO2)2 (2) (L = N2-methyldiethylenetriamine] have been synthesized and their X-ray single crystal structures have been determined. The triamines are ligated to NiII s-facially in (1) and meridionally in (2), with a NiN6 chromophore in each complex.
  • No Thumbnail Available
    Item
    A three dimensional network of Cadmium"
    (Wiley, 1999) Laskar, Inamur Rahaman
    In attempts to build molecular materials with interesting properties, such as catalysis clathration etc., much attention has been given to the synthesis of one-, two- and three-dimensional extended solids involving cadmium. Rigid bridged ligands are frequently employed to construct these materials (Abrahams et al., 1994[Abrahams, B. F., Hardie, M. J., Hoskins, B. F., Robson, R. & Sutherland, E. E. (1994). J. Chem. Soc. Chem. Commun. pp. 1049-1050.]; Soma et al., 1994[Soma, T., Yuge, H. & Iwamoto, T. (1994). Angew. Chem. Int. Ed. Engl. 33, 1665-1666.]; Fujita et al., 1994[Fujita, M., Kwon, Y. J., Miy­aza­wa, M. & Ogura, K. (1994). J. Chem. Soc. Chem. Commun. pp. 1977-1978.]; Yuge & Iwamoto, 1995[Yuge, H. & Iwamoto, T. (1995). Acta Cryst. C51, 374-377.]). The ambidentate thio­cyanate ion which is usually S-bonded to a soft and N-bonded to a hard metal centre can also act as a bridging bidentate ligand to satisfy the coordination number of the metal ion, although the thio­cyanate anion has not been widely used in the construction of inorganic polymeric networks. In order to synthesize uncharged three-dimensional polymers where channels remain unblocked by anions and free for solvent inclusion, we have chosen cadmium(II) thio­cyanate as an effective building block. Cadmium is well suited to this as its d10 configuration permits a wide variety of symmetries and coordination numbers. Recently, we reported the syntheses of the inorganic polymer [Cd3(dien)2(μ-NCS)6]n·nH2O (dien is diethyl­enetri­amine), (II[link]) (Mondal et al., 1999[Mondal, A., Mostafa, G., Ghosh, A., Laskar, I. R. & Ray Chaudhuri, N. (1999). J. Chem. Soc. Dalton Trans. pp. 9-10.]), which utilizes the full bridging potential of the anion. The structure of complex (II[link]) is a polymeric network which contains solvent-filled channels. Channel-containing solids have been and continue to be investigated intensively because of their potential applications, viz. as heterogeneous catalysts and molecular sieves. As part of a continuing investigation into control over the channels, we are currently studying the corresponding cadmium compounds. In this paper, we report the structure of the title CdII complex (I[link]), where medien [medien is N,N-bis(2-amino­ethyl)­methyl­amine] ligands replace the dien ligands of complex
  • No Thumbnail Available
    Item
    Reaction of Aryl and Heterocyclylhydrazines with 2-Methylchromone: Structural Investigation of the Products
    (Taylor & Francis, 1996) Kumar, Dalip
    Reaction of 2-methylchromone (2) with phenylhydrazine provides 3-methyl-5-(o-hydroxyphenyl)-1-phenylpyrazole (6) as a major product. In contrast under similar conditions, heterocyclylhydrazines (8a-c) yield exclusively 5-ethyl-3-(o-hydroxyphenyl)-1-heterocyclylpyrazoles (9a-c). The structural assignments are based on an unambiguous synthesis and an analysis of NMR (1H & 13C) spectral data.