Structural and conductivity studies in LiFeP2O7, LiScP2O7, and NaScP2O7

Structural studies of LiScP₂O₇ by Rietveld refinement confirm that this material is isostructural with LiFeP₂O₇ studied previously. However, NaScP₂O₇ shows a structure different from the structural types of the basic group of Na^IM^IIIP₂O₇ known thus far. Systematic ranges for the six structural types of A^IM^IIIP₂O₇ are presented in terms of ion radii sums and ratios. The framework of LiMP₂O₇ (M=Sc, Fe) has rather wide tunnels running along the crystallographic c-axis. This feature has determined our interest to check the ion conductivity in A^IM^IIIP₂O₇ (A=Li, Na; M=Sc, Fe). The bulk conductivity, however, is low in these compounds, 10⁻⁶–10⁻⁷ S/cm at 300 °C, as determined by impedance spectroscopy. In order to facilitate the conductivity via normal lithium sites, heterovalent substitution is used. Received: 30 April 1999 / Accepted: 15 June 1999     

Structural studies of the Klebsiella type 57 capsular polysaccharide.

The structure of the capsular polysaccharide from Klebsiella type 57 has been investigated. Methylation analysis, uronic acid degradation, modified Smith degradation and graded acid hydrolysis were the principle methods used. Pure oligomeric fragments were isolated using the three methods of degradation and characterized by chemical and physical methods. These studies show the structure to consist of a tetrasaccharide repeating unit (all sugar residues have the D-configuration and are pyranosidic).     

Laser Raman studies on compounds 7.O4O.7 and 7.O5O.7

Laser Raman studies on two compounds of the α,ω-bis(4-alkylanilinebenzylidene -4′-oxy)alkane series were carried out in the spectral regions 1140–1220 and 1550–1650 cm^-1 as a function of temperature. Compounds 7.O4O.7 and 7.O5O.7, exhibit SmA and SmF phases. The structural differences between these liquid crystal dimers, having either an odd or an even number of carbon atoms in the spacer, are remarkably existent in the room temperature Raman spectra. The results are rationalized on the basis of the tendency of these compounds to exhibit bent shapes, and how this manifests in the odd-even effect at the molecular level assuming a semi-rigid core region of the dimeric molecule. It is found that the behaviour of the odd spacer dimer (7.O5O.7) agrees with the molecular model, whereas the even spacer dimer (7.O4O.7) behaves in a similar fashion to monomeric compounds such as the nO.m. compounds. In both cases, dynamic changes around the C=N bond have a profound effect both on the molecular shape in the different phases and on phase behaviour.     

Structural studies of palladium complexes with ligands containing the amide group

Summary Complexes of palladium(II) with 2-(acetylamino)benzoic acid, 2-(benzoylamino)benzoic acid, 2-[2-aminobenzoylamino]benzoic acid, 2-hydroxy benzanilide, 2-mercapto benzanilide, maleanilic acid, 2-(amino carbonyl)benzoic acid, 2-[(phenylamino)carbonyl]benzoic acid, 2-[(1-naphthalenylamino)carbonyl]benzoic acid, 2-[(2-aminophenylamino)carbonyl]benzoic acid, salicylanilide, 2-(aminobenzoyl)benzoic acid and 2-aminobenzamide have been prepared and characterized by chemical analyses, molar conductivity measurements, thermal data and i.r., electronic and n.m.r. spectra.     

Structural studies of group 1 metal 4-azapentalenyl complexes

The first structurally authenticated 4-azapentalenyl complexes are reported, along with DFT studies, that reveal tendencies for their cyclopentadienyl isostructural nature and an ability to exhibit binding modes of varying hapticity.     

Structural and impedance analysis of LiBiP2O7

A new material LiBiP₂O₇ was prepared by solid-state reaction method. The XRD analysis confirms the formation of the sample. The Raman analysis indicates the presence of characteristic bands for a (P₂O₇)⁴⁻ group in the sample. The electrical characterization was carried out using the impedance spectroscopy method in the frequency range of 1 KHz–5 MHz. The bulk conductivity of the material was extracted from the impedance analysis and was found to be in the order of 10⁻⁷ Ω ⁻¹ cm⁻¹ at 473 K. The activation energy was calculated from the Arrhenius plot and was found to be 0.37 eV. The modulus peak maximum shifts to higher frequencies with an increase in temperature and the broad nature of the peaks indicates the non-debye nature of the material. The high value for the activation energy calculated from the conductance spectrum indicates that some energy has been utilized in the creation of charge carriers.     

Comparative experimental optical studies on 7.O5O.7 dimeric liquid crystal compound using theoretical models

In the present study, the optical properties of the 7.O5O.7 dimeric compound are reported. This dimeric compound exhibits typical smectic A to smectic F phase transition, and the main focus of our study is to observe the optical behaviour in SmA phase. In the dimeric compound, the two mesogens are connected by a linkage group or spacer. The presence of the linkage group and the terminal alkyl chains plays a vital role to change the behaviour of this compound as compared to the traditional monomeric compounds. Study of birefringence, refractive indices and normalised polarisation are essential to investigate the optical nature in liquid crystalline compounds. The optical study in our compound is carried out by using the thin prism experimental method with the help of He-Ne laser of wavelength 633 nm. Four-parameter model was used to obtained theoretically measured refractive indices and birefringence data. The theoretical results are then compared with the experimental results. Both the experimentally and theoretically calculated results are properly fitted in our dimeric compound.     

Structural investigations and luminescence of In2Ge2O7 and In2Si2O7

The crystal structures of the ordinary pressure forms of indium digermanate In₂Ge₂O₇ and disilicate In₂Si₂O₇ have been studied from X-ray powder diffraction data by Rietveld refinement. They are closely related to that of the thortveitite which crystallizes in the monoclinic system with the space group C2/m and Z = 2. They show luminescence properties below 160 K and 200 K respectively. The luminescence is discussed in terms of crystal structure and compared to that of some other luminescent indium oxides.     

Structural studies of new group 6 complexes of salicylidene-2-aminopyridine

Interaction of salicylidene-2-aminopyridine (Hsap) with [M(CO)₆], M = Cr, Mo and W, in THF under sunlight resulted in formation of dinuclear complexes [Cr₂O₄(sap)], 1, [Mo₂O₄(sap)], 2, and [W₂O₅(sap)₂], 3. Elemental analysis, spectroscopic and magnetic studies of the reported complexes revealed the proposed structures. Magnetic studies of 1 and 2 suggested that the two metal centers have +3 and +6 formal oxidation states, while the tungsten complex 3 has +6 formal oxidation state with d⁰ electron configuration. The thermal properties of the complexes were investigated by thermogravimetry.