Search results for "bond"
showing 10 items of 3527 documents
Dithiosquarate (dtsq) complexes of nickel(II). Syntheses and crystal structures of [Ni(phen)2(1,2-dtsq)]·3.5H2O, [Ni(phen)2(1,3-dtsq)] and [Ni(tren)(…
2003
Abstract The new nickel(II) complexes [Ni(phen)2(1,2-dtsq)]·3.5H2O (1), [Ni(phen)2(1,3-dtsq)] (2) and [Ni(tren)(1,2-dtsq)] (3) [1,2-dtsq=dianion of 3,4-dimercapto-3-cyclobutene-1,2-dione, 1,3-dtsq=dianion of 3-hydroxy-4-mercapto-2-thioxo-3-cyclobuten-1-one, phen=1,10-phenanthroline and tren=tris(2-aminoethyl)amine] have been synthesized and characterized by single-crystal X-ray diffraction. Their structures are made up of neutral [Ni(phen)2(1,n-dtsq)] [1 (n=2) and 2 n=3)] and [Ni(tren)(1,2-dtsq)] (3) mononuclear units. The nickel atom is six-coordinated in all three cases: four nitrogen atoms from two bidentate phen (1 and 2) or a tetradentate tren (3) groups and either two sulfur (1 and 3)…
Syntheses, structural characterisation and magnetic properties of Fe(ii) and Mn(ii) compounds with the pentacyanopropenido ligand; structural charact…
2006
International audience; Reactions between the metal(II) salts [M(CH3CN)n](BF4)2 (M = Fe, n = 6; M = Mn, n = 4) and some organic anionic polynitriles were studied. With the pentacyanopropenide anion pcp− [pcp− = (NC)2CC(CN)C(CN)2−], were obtained, according to the experimental conditions, the new complexes [M(pcp)2(H2O)4] (1, M = Fe; 2, M = Mn) and [M(pcp)2] (3, M = Fe; 4 = Mn). Use of the hexacyano-3,4-diazahexadienediide anion [(NC)2CC(CN)NNC(CN)C(CN)22−] instead of pcp− did not afford polynitrile metal complexes but led to a new organic derivative 5, of formula C10N8H2. Crystallographic studies indicated that the isostructural compounds 1 and 2 involve discrete monomeric units with pcp li…
Preparation and structural studies on the tBu2Sn(IV) complexes with aromatic mono- and dicarboxylic acids containing hetero {N} donor atom
2004
Nine complexes of 'Bu2Sn(IV)(2+) were obtained in the solid state with ligands containing -COOH group(s) and aromatic (N) donor atom. The binding sites of the ligands were identified by FT-IR spectroscopic measurements. It was found that in most cases the -COO- groups are co-ordinated in monodentate manner. Nevertheless, in some of our complexes, the -COO- group forms bridges between two central {Sn} atoms resulting in the formation of an oligomeric structure, a motif that is characteristic only to the nicotinate compound. These pieces of information and the rationalisation of the experimental Sn-119 Mossbauer nuclear quadrupole splittings, Delta, - according to the point charge model forma…
Multiple Roles of Isocyanides in Palladium-Catalyzed Imidoylative Couplings: A Mechanistic Study
2016
International audience; Kinetic, spectroscopic and computational studies examining a palladium-catalyzed imidoylative coupling highlight the dual role of isocyanides as both substrates and ligands for this class of transformations. The synthesis of secondary amides from aryl halides and water is presented as a case study. The kinetics of the oxidative addition of ArI with RNC-ligated Pd-0 species have been studied and the resulting imidoyl complex [(ArC=NR)Pd(CNR)(2)I] (Ar=4-F-C6H4, R = tBu) has been isolated and characterized by X-ray diffraction. The unprecedented ability of this RNC-ligated imidoyl-Pd complex to undergo reductive elimination at room temperature to give the amide in the p…
Antibacterial Properties of Nanoparticles in Dental Restorative Materials. A Systematic Review and Meta-Analysis
2020
Background and Objectives: Nanotechnology has become a significant area of research focused mainly on increasing the antibacterial and mechanical properties of dental materials. The aim of the present systematic review and meta-analysis was to examine and quantitatively analyze the current evidence for the addition of different nanoparticles into dental restorative materials, to determine whether their incorporation increases the antibacterial/antimicrobial properties of the materials. Materials and Methods: A literature search was performed in the Pubmed, Scopus, and Embase databases, up to December 2018, following PRISMA (Preferred Reporting Items for Systematic Review and Meta-Analysis) …
[1,2,3]Triazolo[1,5-a]pyridines. A theoretical (DFT) study of the ring-chain isomerization
2008
The ring opening isomerization of [1,2,3]triazolo[1,5-a]pyridines to the corresponding 2-pyridyl derivatives has been studied by means of DFT calculations at the B3LYP/6-31+G(d,p) computational level. The effect of the substitution as well as those of protonation, deprotonation, and lithiation on different positions has been studied. The electronic characteristics of the optimized structures have been analyzed by means of the Atoms In Molecules (AIM), Electron Localization Function (ELF), Molecular Electrostatic Potential (MEP), and Natural Bond Orbital (NBO) methodologies. © 2008 Elsevier Ltd. All rights reserved.
On the structure of 3-acetylamino-5-methyl-1,2,4-oxadiazole and on the fully degenerate rearrangements (FDR) of its anion: a stimulating comparison b…
2009
An accurate crystal structure determination has provided evidence for a planar conformation for 3-acetylamino-5-methyl-1,2,4-oxadiazole (5), in agreement with quantum-mechanical calculations in the gas phase. In the crystal, a series of strong intermolecular N7H7….O9 hydrogen bonds link the amido groups of different molecules, causing the formation of infinite parallel ordered chains. The effect of the DMSO solvent on the energy and charge distribution of compound 5 and on its relevant 5− anion, involved in a fully degenerate rearrangement (FDR), has been deepened by quantum-mechanical DFT calculations. The calculated energy barrier for the FDR increases in going from in vacuo to DMSO, in a…
Intra- and intermolecular forces dependent main chain conformations of esters of α,β-dehydroamino acids
2013
Abstract Esters of dehydroamino acids occur in nature. To investigate their conformational properties, the low-temperature structures of Ac-ΔAla-OMe, Ac-ΔVal-OMe, Z-(Z)-ΔAbu-OMe, and Z-(Z)-ΔAbu-NHMe were studied by single-crystal X-ray diffraction. The ΔAla ester prefers the fully extended conformation C5. Both the ΔVal and (Z)-ΔAbu esters assume the conformation β, whereas the amide analogue of the latter prefers the conformation α. For the conformations found, DFT calculations using B3LYP/6-311++G(d,p) with the SCRF-PCM and M062X/6-311++G(d,p) with the SCRF-SMD method were applied to mimicking chloroform and water environment. The tendency of the ΔVal and (Z)-ΔAbu esters towards the confo…
Influence of design mistakes and material degradation on the collapse of a long-span RC roof in South Italy
2020
Abstract In 2004, during ordinary maintenance work, consisting in the waterproofing of a building located in the South of Italy, the long-span (14.50 m) in situ cast reinforced concrete (RC) roof partially collapsed. The building, constructed in 1950, was in service as a cinema up to 1967 and utilized as a school up to 1985. Finally, it was a hotel up to 2000. In 2004, when the building was not in service and underwent maintenance work, it partially collapsed under the dead load. After the collapse, which involved a large portion of the roof, several beams and two columns, the Court nominated a first Official Technical Consultant in order to investigate on the causes of failure and related …
STATE OF THE ART ON BOND BETWEEN FRCM SYSTEMS AND MASONRY/CONCRETE SUBSTRATE: DATABASE ANALYSIS AND IMPROVED MODELS
2023
The use of the Fabric Reinforced Cementitious Mortars (FRCMs) is nowadays a promising solution for the strengthening of both reinforced concrete and masonry structural elements. The application consists of a bond-dependent face-to-face plastering of an open grid or mesh by means of an inorganic-based matrix, i.e. a cement-based mortar. The main advantage of such a strengthening technique is the good compatibility with different types of substrates since the most suitable matrix can be selected focusing on the most similar breathability and stiffness. On the other side, the strengthening efficiency could be over-estimated if the potential bond failure is neglected. The FRCM-bond behaviour de…