Search results for "crystal-structure"
showing 10 items of 61 documents
Cation Environment of BaCeO3−Based Protonic Conductors II: New Computational Models
2011
Quantum chemical calculations have been carried out to simulate Y-doped BaCeO(3) derivatives. Hartree-Fock energy functional was used to study octahedral site environments embedded in a Pmcn orthorhombic framework, showing local arrangement characterized by Ce-O-Ce, Ce-O-Y, and Y-O-Y (Z-O-Ξ) configurations and including or not hydrogen close to the moieties encompassing those configurations. The latter are, in fact, representative of - and, in our modeling approach, were treated as - local arrangements that could be found in Y:BaCeO(3)-doped materials. The geometrical optimizations performed on the structural models and a detailed orbital analysis of these systems allowed us to confirm and …
Experimental and Theoretical Investigations on Structural and Vibrational Properties of Melilite-Type Sr2ZnGe2O7 at High Pressure and Delineation of …
2015
We report a combined experimental and theoretical study of melilite-type germanate, Sr2ZnGe2O7, under compression. In situ high-pressure X-ray diffraction and Raman scattering measurements up to 22 GPa were complemented with first-principles theoretical calculations of structural and lattice dynamics properties. Our experiments show that the tetragonal structure of Sr2ZnGe2O7 at ambient conditions transforms reversibly to a monoclinic phase above 12.2 Gpa with similar to 1% volume drop at the phase transition pressure. Density functional calculations indicate the transition pressure at, similar to 13 GPa, which agrees well with the experimental value. The structure of the high-pressure mono…
Assembly-Induced Bright-Light Emission from Solution-Processed Platinum(II) Inorganic Polymers
2019
Synthesis, processing, and characterization are reported for a series of tetracyanoplatinate Magnus' salt (TCN-MS) derivatives-soluble derivatives of the generally intractable Magnus' green salt-that feature the general structure [Pt(NH2R)(4)] [Pt(CN)(4)] where R is a branched alkyl group or a w-phenylalkyl group. In solutions, these coordination compounds generally dissolve on the level of individual ion pairs as shown by X-ray diffraction analysis. To enable the formation of quasi-one-dimensional linear stacks of Pt(II) atoms in thin films, the matrix-assisted assembly is employed, whereby the compounds are codissolved with poly(ethylene oxide) (PEO), followed by film casting, thermally a…
Phase behaviour of Ag2CrO4 under compression: Structural, vibrational, and optical properties
2013
We have performed an experimental study of the crystal structure, lattice dynamics, and optical properties of silver chromate (Ag2CrO4) at ambient temperature and high pressures. In particular, the crystal structure, Raman-active phonons, and electronic band gap have been accurately determined. When the initial orthorhombic Pnma Ag2CrO4 structure (phase I) is compressed up to 4.5 GPa, a previously undetected phase (phase II) has been observed with a 0.95% volume collapse. The structure of phase II can be indexed to a similar orthorhombic cell as phase I, and the transition can be considered to be an isostructural transition. This collapse is mainly due to the drastic contraction of the a ax…
Influence of antibody binding on oxygen binding behavior of Panulirus interruptus hemocyanin
1997
Oxygen binding behavior of monomeric subunit a and the hexameric form of this subunit of hemocyanin of Panulirus interruptus is influenced by the binding of various monoclonal antibodies. These antibodies react with other surface parts of the subunit than its second domain in which the oxygen binding site is located. The influence of three monoclonal antibodies and their antigen binding fragments (F-ab) has been investigated. Two antibodies increase the oxygen affinity of monomeric hemocyanin from that observed in its low affinity T-state, while the third has little influence on this property. F-ab fragments abolish almost completely the cooperativity of oxygen binding by the hexameric hemo…
Infinite coordination polymer networks metallogelation of aminopyridine conjugates and in situ silver nanoparticle formation
2018
Herein we report silver(i) directed infinite coordination polymer network (ICPN) induced self-assembly of low molecular weight organic ligands leading to metallogelation. Structurally simple ligands are derived from 3-aminopyridine and 4-aminopyridine conjugates which are composed of either pyridine or 2,2'-bipyridine cores. The cation specific gelation was found to be independent of the counter anion, leading to highly entangled fibrillar networks facilitating the immobilization of solvent molecules. Rheological studies revealed that the elastic storage modulus (G') of a given gelator molecule is counter anion dependent. The metallogels derived from ligands containing a bipyridine core dis…
A Multivariate Analysis of HIV-1 Protease Inhibitors and Resistance Induced by Mutation
2005
This paper describes the use of the multivariate statistical procedure principal component analysis as a tool to explore the inhibitory activity of classes of protease inhibitors (PIs) against HIV-1 viruses (wild type and more-frequent single mutants, V82A, V82F, and I84V) and against protease enzymes. The analysis of correlations between biological activity and molecular descriptors or similarity indexes allowed a reliable classification of the 51 derivatives considered in this study. The best results were obtained in the case of the I84V mutant for which a high number of predictions was achieved. On this basis, this statistical approach is proposed as a reliable method for the prediction …
NaI/CuI–II heterometallic cages interconnected by unusual linear 2-coordinate OCN-Cu(I)-NCO links: synthesis, structural, magnetostructural correlati…
2009
A new Na(I)/Cu(I-II) heterometallic coordination complex [Cu(2)L(2)Na(NCO)(2)Cu](n) (1) with an unusual architecture has been synthesised. In 1 cyclic Na-O-Cu-O-Cu cages constructed by the tetradentate N(2)O(2) donor Schiff base ligand (H(2)L = N, N'-bis(2-hydroxyacetophenone) propylenediimine) are interconnected to each other by a rare singly end-to-end bridged OCN-Cu(I)-NCO link generating 1D chain. The complex has been characterised by elemental, spectral and structural analysis. The cyclic voltammogram of 1 has been compared with the analogous complexes. Cryomagnetic susceptibility studies indicate the copper(II) centers in the cyclic Na-O-Cu-O-Cu cages are antiferromagnetically coupled…
Four-, five- and six-coordinated Zn-II complexes of OH-containing ligands: Syntheses, structure and reactivity
2002
Four-, five- and six-coordinated complexes of Zn-II with OH-rich molecules possessing an ONO binding core were synthesized, characterized and their structures were established by single-crystal X-ray diffraction, The corresponding metal ion geometries were found to be distorted tetrahedral, square pyramidal and octahedral, respectively. The complexes exhibit interesting lattice structures such as layered and corrugated sheets owing to the presence of a number of weak intermolecular interactions. The five-coordinated, water-bound Zn-II complex was studied because of its putative hydrolysis property towards p-nitrophenyl acetate. (C) Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.
Inclusion complexes of Cethyl-2-methylresorcinarene and pyridine N-oxides: breaking the C–I⋯−O–N+ halogen bond by host–guest complexation
2016
C ethyl-2-Methylresorcinarene forms host–guest complexes with aromatic N-oxides through multiple intra- and intermolecular hydrogen bonds and C–H⋯π interactions. The host shows conformational flexibility to accommodate 3-methylpyridine N-oxide, while retaining a crown conformation for 2-methyl- and 4-methoxypyridine N-oxides highlighting the substituent effect of the guest. N-Methylmorpholine N-oxide, a 6-membered ring aliphatic N-oxide with a methyl at the N-oxide nitrogen, is bound by the equatorial −N–CH3 group located deep in the cavity. 2-Iodopyridine N-oxide is the only guest that manifests intermolecular N–O⋯I–C halogen bond interactions, which are broken down by the host resulting i…