Search results for "CRYSTALLOGRAPHY"
showing 10 items of 18525 documents
Layered Double Hydroxides: A Toolbox for Chemistry and Biology
2019
Layered double hydroxides (LDHs) are an emergent class of biocompatible inorganic lamellar nanomaterials that have attracted significant research interest owing to their high surface-to-volume ratio, the capability to accumulate specific molecules, and the timely release to targets. Their unique properties have been employed for applications in organic catalysis, photocatalysis, sensors, drug delivery, and cell biology. Given the widespread contemporary interest in these topics, time-to-time it urges to review the recent progresses. This review aims to summarize the most recent cutting-edge reports appearing in the last years. It firstly focuses on the application of LDHs as catalysts in re…
X-Ray characterization of 3-methyl-6,8-di(2-pyridyl)-[1,2,3]triazolo[5',1':6,1]pyrido[2,3-d]pyrimidine
2005
Abarca Gonzalez, Belen. Belen.Abarca@uv.es ; Ballesteros Campos, Rafael, Rafael.Ballesteros@uv.es ; Chadlaoui, Mimoun, michad@alumni.uv.es ; Ramirez de Arellano Sanchez, Maria del Carmen, Ramirezdearellano@uv.es
Modification of the Structure and Nano-Mechanical Properties of LiF Crystals Under Irradiation with Swift Heavy Ions
2011
The modifications of the structure and hardness of LiF crystals under high-fluence irradiation with MeV- and GeV-energy Au ions have been studied using nanoindentation and atomic force microscopy. The formation of ion-induced dislocations and bulk nanostructures consisting of grains with nanoscale dimensions (50 nm - 100 nm) has been observed. The structural modifications are accompanied by a strong ion-induced hardening which is related to dislocation impeding by assemblies of defect aggregates, dislocation loops of vacancy and interstitial types and grain boundaries. For MeV ions, the modifications are localized in a thin surface layer (few mm) where much higher density of deposited energ…
New Insights into the complexation of lead(II) by 1,4,7,10-tetrakis(carbamoylmethyl)-1,4,7,10-tetraazacyclododecane (DOTAM): structural, thermodynami…
2007
The lead(II) coordination properties of the tetrapodal ligand DOTAM [1,4,7,10-tetrakis(carbamoylmethyl)-1,4,7,10-tetraaza-cyclododecane] have been investigated both in the solid state and in solution in order to ascertain the stereoactivity of the lone pair and to rationalize the structural effects of a cyclen-based scaffold on the metal uptake kinetics. The crystal structure of the free base shows that the pendant acetamide groups are not equivalent: two are folded over the macrocycle and maintained by an intramolecular hydrogen bond involving an amide hydrogen atom and a neighboring tertiary amine of the cyclen ring, while the other two are extended and point away from the macrocyclic cav…
Probing the Extremes of Covalency in M-Al bonds: Lithium and Zinc Aluminyl Compounds.
2022
Synthetic routes to lithium, magnesium, and zinc aluminyl complexes are reported, allowing for the first structural characterization of an unsupported lithium-aluminium bond. Crystallographic and quantum-chemical studies are consistent with the presence of a highly polar Li-Al interaction, characterized by a low bond order and relatively little charge transfer from Al to Li. Comparison with magnesium and zinc aluminyl systems reveals changes to both the M-Al bond and the (NON)Al fragment (where NON=4,5-bis(2,6-diisopropylanilido)-2,7-di-tert-butyl-9,9-dimethylxanthene), consistent with a more covalent character, with the latter complex being shown to react with CO<sub>2</sub> vi…
Development of ultrasound-assisted digestion methods for the determination of toxic element concentrations in ash samples by ICP-OES
2011
The present thesis introduces several ultrasound-assisted digestion methods developed for the determination of toxic element concentrations in ash samples by inductively coupled plasma optical emission spectrometry (ICP-OES). Ultrasound-assisted digestion is a quite new technique used for sample pre-treatment purposes, especially in difficult sample matrixes. Elements determined are As, Ba, Co, Cr, Cu, Ni, Pb, Sb, Sr, V, and Zn. Most of the elements determined exist at a trace or ultra trace level in ashes and most are potential risks in the environment or human body even at low concentrations. Most of the selected elements can be determined directly by ICP-OES, but for the determination of…
Crystalline forms of selected agrochemical actives : design and synthesis of cocrystals
2012
The research described in this disseration covers the crystal form screening of two analogous agrochemical actives, thiophanate-methyl and thiophanate-ethyl, as well as the discovery of seven 4-hydroxybenzoic acid cocrystals of selected agrochemical actives. Polymorphs are crystal forms of a compound that have the same composition, but a different arrangement of molecules. Cocrystals are molecular crystals composed of two or more compounds, and refer mainly to crystals which contain compounds that are solids at standard conditions. Solvates are forms that have molecules of solvent in the crystal lattice and these include hydrates, in which the solvent is water. The crystal forms of organic …
Magneto-Structural Properties and Theoretical Studies of a Family of Simple Heterodinuclear Phenoxide/Alkoxide Bridged MnIIILnIII Complexes : On the …
2018
A family of MnIIILnIII strictly dinuclear complexes of general formula [MnIII(μ-L)(μ-OMe)(NO3)LnIII(NO3)2(MeOH)] (LnIII = Gd, Dy, Er, Ho) has been assembled in a one pot synthesis from a polydentate, multipocket aminobis(phenol)ligand [6,6'-{(2-(1-morpholyl)ethylazanediyl)bis(methylene)}bis(2-methoxy-4-methylphenol)], Mn(NO3)2·4H2O, Ln(NO3)3· nH2O, and NEt3 in MeOH. These compounds represent the first examples of fully structurally and magnetically characterized dinuclear MnIIILnIII complexes. Single X-ray diffraction studies reveal that all complexes are isostructural, consisting of neutral dinuclear molecules where the MnIII and LnIII metal ions, which exhibit distorted octahedral MnN2O4 …
Room-Temperature Magnetic Bistability in a Salt of Organic Radical Ions
2021
International audience; Cocrystallization of 7,7′,8,8′-tetracyanoquinodimethane radical anion (TCNQ −•) and 3-methylpyridinium-1,2,3,5dithiadiazolyl radical cation (3-MepyDTDA +•) afforded isostructural acetonitrile (MeCN) or propionitrile (EtCN) solvates containing cofacial π dimers of homologous components. Loss of lattice solvent from the diamagnetic solvates above 366 K affords a high-temperature paramagnetic phase containing discrete TCNQ −• and weakly bound π dimers of 3-MepyDTDA +• , as evidenced by X-ray diffraction methods and magnetic susceptibility measurements. Below 268 K, a first-order phase transition occurs, leading to a low-temperature diamagnetic phase with TCNQ −• σ dimer…
Ligand mediated evolution of size dependent magnetism in cobalt nanoclusters.
2018
We use density functional theory to model the impact of a ligand shell on the magnetic properties of CoN (15 ≤ N ≤ 55) nanoclusters. We study three different ligand shells on each nanocluster core size, each known to have different electronic interactions with the surface: pure Cl ligand shells (X-type), pure PH3 ligand shells (L-type), and two component ligand shells with mixtures of Cl and PH3 ligands. The simulations show that the identity, arrangement, and total coverage of the ligand shell controls the distribution of local magnetic moments across the CoN core. On the surface of an unpassivated CoN nanocluster, the Co-Co coordination number (CN) is known to determine the local magnetic…