Search results for "cyclic"
showing 10 items of 2439 documents
Nickel as a Lewis Base in a T‐Shaped Nickel(0) Germylene Complex Incorporating a Flexible Bis(NHC) Ligand
2018
Flexible, chelating bis(NHC) ligand 2, able to accommodate both cis- and trans-coordination modes, was used to synthesize (2)Ni(η 2 -cod), 3. In reaction with GeCl2, this produced (2)NiGeCl2, 4, featuring a T-shaped Ni(0) and a pyramidal Ge center. Complex 4 could also be prepared from [(2)GeCl]Cl, 5, and Ni(cod)2, in a reaction that formally involved Ni-Ge transmetalation, followed by coordination of the extruded GeCl2 moiety to Ni. A computational analysis showed that 4 possesses considerable multiconfigurational character and the Ni→Ge bond is formed through σ-donation from the Ni 4s, 4p, and 3d orbitals to Ge. (NHC)2Ni(cod) complexes 9 and 10, as well as (NHC)2GeCl2 derivative 11, incor…
1977
Copolymers from styrene and 1-vinylimidazoles (4a–f), form low spin adducts with iron(II) porphyrins and iron(III) porphyrins, when the content of imidazolyl groups in the polymer is ten mole percent or more. With polymers having a content of imidazolyl groups of less then one mole percent, only high spin adducts are observed. With terpolymers, in which the porphyrin is covalently bound to the copolymer the same phenomenon is observed. Only the high spin Fe(II) porphyrin adducts in the solid state adsorb molecular oxygen like cobalt(II) porphyrins under the same conditions. Adsorptions and desorptions of oxygen are much slower in the cases of iron(II) porphyrins than with the cobalt(II) por…
Ring-opening metathesis of some strained bicyclic systems; stereocontrolled access to diolefinated saturated heterocycles with multiple stereogenic c…
2018
Ring-opening metathesis (ROM) of various unsaturated, constrained bicyclic ring systems has been investigated with the use of commercial ruthenium-based catalysts. Starting from various cyclodienes, the corresponding derived bicyclic lactone, lactam, and isoxazoline derivatives were submitted to ROM under ethenolysis. These functionalized, strained bicyclic systems afforded novel highly-functionalized diolefinated heterocyclic scaffolds in ROM reactions with stereocontrol, through the conservation of the configuration of the stereogenic centers of the starting compounds.
MOTION SICKNESS IN CHILDHOOD MIGRAINE
2017
Background: Migraine is a chronic, progressive, and debilitating disorder that has an impact on the lives of millions of individuals. The origins of the disability can be traced into childhood and adolescence for most adult migraine sufferers. The group of periodic syndromes consists in symptoms related to migraine, thought to be migraine equivalent or precursors. Aim of this study is to assess the role of MS as risk factors for childhood migraine. Materials and methods: 441 subjects (211 Females) aged 6-13 years (mean 9.20; SD 2.42), consecutively referred between October 2007 to March 2009 for primary headaches to pediatric Centers for Headache in Childhood. Control group consisted of 365…
Polyamines : études et applications
2008
International audience
Inverted molecular cups: 1-D and 2-D Ag(I) coordination polymers from resorcinarene bis-thiacrowns
2016
Resorcinarene bis-thiacrown hosts 1–3 were prepared and crystallized with silver trifluoroacetate yielding one and two dimensional Ag coordination polymers. The complexation of silver in exo-cavity fashion folds the thiacrown bridges inwards transforming the resorcinarene hosts into inverted molecular cups. The silver cations were coordinated to the resorcinarene ligands and trifluoroacetate anions, which act as monodentate or bidendate bridging ligands between the metal ions. Argentophilic Ag···Ag (2.93–3.38 Å) interactions supported by two bridging carboxylate anions were found in two of the structures, whereas longer Ag···Ag distances were observed if only one anion connected the silver …
On the synthesis of functionalized porphyrins and porphyrin conjugates via β-aminoporphyrins
2016
International audience; The synthesis of functionalized porphyrins and their conjugates from meso-tetraarylporphyrins through the acylation and the oxidation of beta-aminoporphyrins was investigated. 2,3-Dioxochlorins were prepared by the oxidation of a variety of beta-aminoporphyrins and subsequently used in a condensation reaction with functionalized aromatic aldehydes and ammonium acetate to form beta-functionalized porphyrins bearing a fused imidazole ring. Under optimized experimental conditions both reactions tolerate various functional groups and afford the products in an appropriate overall yield. The mildness and usefulness of this methodology are illustrated by several examples in…
Crystal structure and Hirshfeld surface analysis of dimethyl (1R*, 3aS*, 3a(1)R*, 6aS*, 9R*, 9aS*)-3a(1),5,6,9a-tetrahydro-1H,4H,9H-1,3a:6a,9-diepoxy…
2019
The title diepoxyphenalene derivative, C17H18O6, comprises a fused cyclic system containing four five-membered rings (two dihydrofuran and two tetrahydrofuran) and one six-membered ring (cyclohexane). The five-membered dihydrofuran and tetrahydrofuran rings adopt envelope conformations, and the six-membered cyclohexane ring adopts a distorted chair conformation. Two methyl carboxylate groups occupy adjacent positions (2- and 3-) on a tetrahydrofuran ring. In the crystal, two pairs of C-H center dot center dot center dot O hydrogen bonds link the molecules to form inversion dimers, enclosing two R-2(2)(6) ring motifs, that stack along the a-axis direction and are arranged in layers parallel …
Influences of Chemical Functionalities on Crystal Structures and Electrochemical Properties of Dihydro-benzoxazine Dimer Derivatives
2021
Dihydro-1,3,2H-benzoxazine dimer derivatives or dihydro-benzoxazine dimers are a class of compounds typically prepared by ring-opening reactions between dihydro-benzoxazines and phenols. Dihydro-benzoxazine dimers act as chelating agents for several transition and rare-earth cations. To better understand the chelating properties, it is necessary to examine their structural features and electrochemical characteristics thoroughly. However, the electrochemical properties of dihydro-benzoxazine dimers have not been tremendously examined. Herein, eight derivatives of dihydro-benzoxazine dimers possessing different substituents on the benzene ring and the tertiary-amine nitrogen were synthesized …
Crystal structure and Hirshfeld surface analysis of poly[[bis[μ4-N,N′-(1,3,5-oxadiazinane-3,5-diyl)bis(carbamoylmethanoato)]nickel(II)tetrapotassium]…
2021
The complex nickel(II) anion comprises a pseudomacrocyclic hydrazide-based ligand with an L shape. In the crystal, such anions are connected with the potassium cations and the water solvent molecules, forming a three-dimensional polymeric framework, which is stabilized by an extensive system of hydrogen bonds.