Search results for "complex"
showing 10 items of 5889 documents
Chiral Molecular Magnets: Synthesis, Structure, and Magnetic Behavior of the Series [M(L-tart)] (M = MnII, FeII, CoII, NiII;L-tart = (2R,3R)-(+)-tart…
2006
A new series of layered magnets with the formula [M(L-tartrate)] (M = Mn(II), Co(II), Fe(II), Ni(II); L-tartrate = (2R,3R)-(+)-tartrate) has been prepared. All of these compounds are isostructural and crystallize in the chiral orthorhombic space group I222, as found by X-ray structure analysis. Their structure consists of a three-dimensional polymeric network in which each metal shows distorted octahedral coordination bound to four L-tartrate ligands, two of which chelate through an alcohol and a carboxylate group and the other two bind terminally through a monodentate carboxylate group. The chirality of the ligand imposes a Delta conformation on all metal centers. Magnetically, the paramag…
Alkyl Complexes of Rare-Earth Metals That Contain a Furyl-Functionalized Cyclopentadienyl Ligand: Alkyl Cation Formation and Unexpected Ring-Opening…
2003
Rare-earth metal complexes of the type [Ln{η5:η1-C5Me4SiMe2(C4H3O-2)}(CH2SiMe3)2(THF)] (Ln = Y, Lu) were prepared by σ-bond metathesis of [Ln(CH2SiMe3)3(THF)2] with the 2-furyl-functionalized tetramethylcyclopentadiene (C5Me4H)SiMe2(C4H3O-2) and isolated as colorless crystals. Single-crystal X-ray structure analysis of the lutetium complex confirmed the coordination of the furyl group and THF to give a molecule of trigonal bipyramidal geometry with the oxygen donor atoms in the apical positions. The lability of the oxygen donor atoms results in fluxional behavior. Reaction with triphenylborane in THF gave thermally robust mono(alkyl) cations [Ln{η5:η1-C5Me4SiMe2(C4H3O-2)}(CH2SiMe3)(THF)n]+.…
Synthesis and Reaction Chemistry of Sb(ECH2CH2NMe2)3(E= O, S)
2012
The antimony aminoalkoxide and aminothiolates Sb(ECH 2CH 2NMe 2) 3 [E = O (1), S (2)] were synthesized and their ability to form adducts with other metal moieties investigated. Compound 1 forms 1:1 adducts with NiI 2 (3) and M(acac) 2 [M = Cd (4), Ni (5)], while 2 undergoes ligand exchange with AlMe 3 to afford Me 2AlSCH 2CH 2NMe 2 (6). The structures of 2-4 and 6 were determined. Compound 2 incorporates three S, N-chelating ligands though the interaction with nitrogen is weaker than in analogous alkoxide complexes. Product 3 reveals one iodine has migrated from nickel to antimony, and all three alkoxide ligands bridge the two metals through μ 2-O atoms. In contrast, in 4, only one alkoxide…
Linked Benzylamido-Cyclopentadienyl Ligands: Synthesis and Characterization of Alkyl Titanium Complexes
1997
Titanium complexes of the general type Ti(η5:η1-C5H4Si-Me2NCH2C6H3X2-2,5)Cl2 (XH, F), containing a linked benzylamido-cyclopentadienyl ligand, were prepared by reaction of Ti(η5-C5H4SiMe2Cl)Cl3 with lithium amide Li(NHCH2C6H3X2-2,5). A single-crystal X-ray structural analysis of Ti(η5: η1-C5H4SiME2NCH2C6H3F2-2,5)Cl2 revealed a conformation in the solid state in which the aryl ring is turned away from the metal center. Ti(η5:η1-C5H4SiMe2NCH2C6H5)Cl2 can be alkylated with a variety of reagents to form extremely sensitive complexes of the type Ti(η5-C5H4SiMe,2NCH2C6H5)R2 (RMe, CH2 C6H5, CH2SiME3, CH2CMe2C6H5). Reaction of Li2[C5Me4SiMe2NCH2C6H5] with TiCl3(THF)3 gave Ti(η5: η1-C5Me4SiMe2NCH2C6…
De-epoxidation of Violaxanthin after Reconstitution into Different Carotenoid Binding Sites of Light-harvesting Complex II
2001
In higher plants, the de-epoxidation of violaxanthin (Vx) to antheraxanthin and zeaxanthin is required for the pH-dependent dissipation of excess light energy as heat and by that process plays an important role in the protection against photo-oxidative damage. The de-epoxidation reaction was investigated in an in vitro system using reconstituted light-harvesting complex II (LHCII) and a thylakoid raw extract enriched in the enzyme Vx de-epoxidase. Reconstitution of LHCII with varying carotenoids was performed to replace lutein and/or neoxanthin, which are bound to the native complex, by Vx. Recombinant LHCII containing either 2 lutein and 1 Vx or 1.6 Vx and 1.1 neoxanthin or 2.8 Vx per mono…
The Binding of Xanthophylls to the Bulk Light-harvesting Complex of Photosystem II of Higher Plants
2002
The pigment composition of the light-harvesting complexes (LHCs) of higher plants is highly conserved. The bulk complex (LHCIIb) binds three xanthophyll molecules in combination with chlorophyll (Chl) a and b. The structural requirements for binding xanthophylls to LHCIIb have been examined using an in vitro reconstitution procedure. Reassembly of the monomeric recombinant LHCIIb was performed using a wide range of native and nonnative xanthophylls, and a specific requirement for the presence of a hydroxy group at C-3 on a single β-end group was identified. The presence of additional substituents (e.g.at C-4) did not interfere with xanthophyll binding, but they could not, on their own, supp…
Chemical Applications of Mössbauer Spectroscopy
2012
The Tutorial Lecture begins with a brief recapitulation of the hyperfine interactions and the relevant parameters observable in a Mossbauer spectrum. The main chapter with selected examples of chemical applications of Mossbauer spectroscopy follows and is subdivided into sections on: basic information on structure and bonding; switchable molecules (thermal spin transition in mono- and oligonuclear coordination compounds, light-induced spin transition, nuclear-decay-induced spin transition, spin transition in metallomesogens); mixed-valency in biferrocenes and other iron coordination compounds, and in an europium intermetallic compound; electron transfer in Prussian blue-analog complexes; mo…
Supramolecular coordination chemistry of aromatic polyoxalamide ligands: A metallosupramolecular approach toward functional magnetic materials
2010
Abstract The impressive potential of the metallosupramolecular approach in designing new functional magnetic materials constitutes a great scientific challenge for the chemical research community that requires an interdisciplinary collaboration. New fundamental concepts and future applications in nanoscience and nanotechnology will emerge from the study of magnetism as a supramolecular function in metallosupramolecular chemistry. Our recent work on the rich supramolecular coordination chemistry of a novel family of aromatic polyoxalamide (APOXA) ligands with first-row transition metal ions has allowed us to move one step further in the rational design of metallosupramolecular assemblies of …
Effect of over the counter mouthwashes with and without alcohol on sorption and solubility of bulk fill resins
2020
Background Composites sorption and solubility can be precursors of several chemical and physical processes, which lead to deleterious effects on the polymer structure. This study evaluated the effect of mouthwashes with and without alcohol on the sorption and solubility of conventional and low viscosity bulk fill resins. Material and Methods Four types of Bulk Fill resins (Filtek™ Bulk Fill, X-tra Fil, Filtek™ Bulk Fill Flow and X-tra Base) were submitted to the following mouthwashes: Listerine Cool Mint and Periogard (containing alcohol) and Listerine Zero and Periogard (alcohol-free). The specimens were stored in the mouthwashes for seven days. Solubility and sorption tests were performed…
A fluorinated 2D magnetic coordination polymer
2021
Herein we show the versatility of coordination chemistry to design and expand a family of 2D materials by incorporating F groups at the surface of the layers. Through the use of a prefuntionalized organic linker with F groups, it is possible to achieve a layered magnetic material based on Fe(ii) centers that are chemically stable in open air, contrary to the known 2D inorganic magnetic materials. The high quality of the single crystals and their robustness allow to fabricate 2D molecular materials by micromechanical exfoliation, preserving the crystalline nature of these layers together with the desired functionalization.