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FeIII Ions (feiii + ion)
Selected AbstractsSynthesis and Characterization of Metal-Centered, Six-Membered, Mixed-Valent, Heterometallic Wheels of Iron, Manganese, and Indium,CHEMISTRY - A EUROPEAN JOURNAL, Issue 9 2006Rolf W. Saalfrank Prof. Dr. Abstract Heptanuclear metal-centered, six-membered, mixed-valent, heterometallic wheels 1,3 of iron, manganese, and indium were prepared in a one-pot reaction from N -benzyldiethanolamine (H2L1), cesium carbonate, [PPh4]2[MnCl4], and FeCl3 or InCl3. All three complexes were characterized by the combination of elemental analysis, FAB mass spectroscopy, X-ray diffraction and cyclic voltammetry. and in the case of 1 additionally by Mössbauer spectroscopy. In 1, four MnII ions in the periphery are arranged in pairs alternating with one FeIII ion each, with an FeIII ion located in the center. In 2, three MnII ions alternate with three InIII ions, whereas in 3, four InIII ions are arranged in pairs and alternate with one MnII ion each. In 2 and 3 an MnII ion is encapsulated in the center. [source] Self-Assembly from Discrete Clusters to 2D Network Based on [Fe(phen)(CN)4], and [Fe(bipy)(CN)4],: Synthesis, Structures and Magnetic PropertiesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 14 2009Hua Xiang Abstract A series of cyanido-bridged complexes {[FeIII(phen) (CN)4]2[NiL1]}·4H2O (1), {[FeIII(bipy)(CN)4]2[NiL1]}·4H2O (2), [FeIII(bipy)(CN)4]2[NiL2] (3), {[FeIII(phen)(CN)4]2[CuL3]}·5H2O (4), {[FeII(phen)(CN)4][Ni(ea)2]}2·2H2O (5), {[FeII(phen)(CN)4] [NiL2]·2H2O}n (6), {[FeIII(bipy)(CN)4]2[Ni(H2O)2]}·6.5H2O}n (7) and {[FeII(bipy)(CN)4][Ni(ea)2]·H2O}n (8) were synthesized using H[Fe(phen)(CN)4]·2H2O and H[Fe(bipy)(CN)4]·2H2O as precursors [L1 = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane, L2 = 3,10-bis(2-phenylethyl)-1,3,5,8, 10,12-hexaazacyclotetradecane, L3 = 3,10-bis(2-hydroxyethyl)-1,3,5,8,10,12-hexaazacyclotetradecane, phen = 1,10-phenanthroline, bipy = 2,2,-bipyridine, ea = ethanolamine). Complexes 1,4 are trinuclear clusters, and 5 is a tetranuclear square. In 6, the [FeII(phen)(CN)4]2, anions alternately bridge the [NiL2]2+ cations to generate a 1D wavy chain. The structure of 7 possesses a 4,2-ribbonlike chain, which contains a NiII2(CN)4FeIII2 square with each NiII atom shared by two adjacent squares. Each FeII and NiII atom in 8 acts as a three-connected node through the cyanido-bridges to generate a 2D network with a 4,82 topological net. Ferromagnetic couplings are found between the low-spin FeIII ions and the NiII ions through the cyanido groups in 1,3 and 7, and a metamagnetic behavior and a frequency dependence of the out-of-phase ac susceptibility are observed in 7. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Dendrimer-Functionalized Iron Oxide Nanoparticles for Specific Targeting and Imaging of Cancer Cells,ADVANCED FUNCTIONAL MATERIALS, Issue 16 2007H. Wang Abstract We demonstrated a unique approach that combines a layer-by-layer (LbL) self-assembly method with dendrimer chemistry to functionalize Fe3O4 nanoparticles (NPs) for specific targeting and imaging of cancer cells. In this approach, positively charged Fe3O4 NPs (8.4,nm in diameter) synthesized by controlled co-precipitation of FeII and FeIII ions were modified with a bilayer composed of polystyrene sulfonate sodium salt and folic acid (FA)- and fluorescein isothiocyanate (FI)-functionalized poly(amidoamine) dendrimers of generation 5 (G5.NH2 -FI-FA) through electrostatic LbL assembly, followed by an acetylation reaction to neutralize the remaining surface amine groups of G5 dendrimers. Combined flow cytometry, confocal microscopy, transmission electron microscopy, and magnetic resonance imaging studies show that Fe3O4/PSS/G5.NHAc-FI-FA NPs can specifically target cancer cells overexpressing FA receptors. The present approach to functionalizing Fe3O4 NPs opens a new avenue to fabricating various NPs for numerous biological sensing and therapeutic applications. [source] Structure of magnetic poly(oxyethylene),siloxane nanohybrids doped with FeII and FeIIIJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 4 2003N. J. O. Silva Hybrid organic,inorganic nanocomposites doped with FeII and FeIII ions and exhibiting interesting magnetic properties have been obtained by the sol,gel process. The hybrid matrix of these ormosils (organically modified silicates), classed as di-ureasils and termed U(2000), is composed of poly(oxyethylene) chains of variable length grafted to siloxane groups by means of urea crosslinkages. Iron perchlorate and iron nitrate were incorporated in the di-ureasil matrices, leading to compositions within the range 80 ,n, 10, n being the molar ratio of ether-type O atoms per cation. The structure of the doped di-ureasils was investigated by small-angle X-ray scattering (SAXS). For FeII -doped samples, SAXS results suggest the existence of a two-level hierarchical structure. The primary level is composed of spatially correlated siloxane clusters embedded in the polymeric matrix and the secondary, coarser level consists of domains where the siloxane clusters are segregated. The structure of FeIII -doped hybrids is different, revealing the existence of iron oxide based nanoclusters, identified as ferrihydrite by wide-angle X-ray diffraction, dispersed in the hybrid matrix. The magnetic susceptibility of these materials was determined by zero-field-cooling and field-cooling procedures as functions of both temperature and field. The different magnetic features between FeII - and FeIII -doped samples are consistent with the structural differences revealed by SAXS. While FeII -doped composites exhibit a paramagnetic Curie-type behaviour, hybrids containing FeIII ions show thermal and field irreversibilities. [source] Metal,thiolate bonds in bioinorganic chemistryJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 12 2006Edward I. Solomon Abstract Metal,thiolate active sites play major roles in bioinorganic chemistry. The MSthiolate bonds can be very covalent, and involve different orbital interactions. Spectroscopic features of these active sites (intense, low-energy charge transfer transitions) reflect the high covalency of the MSthiolate bonds. The energy of the metal,thiolate bond is fairly insensitive to its ionic/covalent and ,/, nature as increasing MS covalency reduces the charge distribution, hence the ionic term, and these contributions can compensate. Thus, trends observed in stability constants (i.e., the Irving,Williams series) mostly reflect the dominantly ionic contribution to bonding of the innocent ligand being replaced by the thiolate. Due to high effective nuclear charges of the CuII and FeIII ions, the cupric, and ferric,thiolate bonds are very covalent, with the former having strong , and the latter having more , character. For the blue copper site, the high , covalency couples the metal ion into the protein for rapid directional long range electron transfer. For rubredoxins, because the redox active molecular orbital is , in nature, electron transfer tends to be more localized in the vicinity of the active site. Although the energy of hydrogen bonding of the protein environment to the thiolate ligands tends to be fairly small, H-bonding can significantly affect the covalency of the metal,thiolate bond and contribute to redox tuning by the protein environment. © 2006 Wiley Periodicals, Inc. J Comput Chem 27: 1415,1428, 2006 [source] Two oxo complexes with tetranuclear [Fe4(,3 -O)2]8+ and trinuclear [Fe3(,3 -O)]7+ unitsACTA CRYSTALLOGRAPHICA SECTION C, Issue 7 2006Ana María Atria Two new oxo complexes, namely hexa-,2 -acetato-acetatoaquabis(di-3-pyridylamine)di-,3 -oxo-tetrairon(III) chloride monohydrate ethanol 1.25-solvate, [Fe4(C2H3O2)7O2(C10H9N3)2(H2O)]Cl·1.25C2H6O·H2O, (I), containing a tetranuclear [Fe4(,3 -O)2]8+ unit, and 2-methylimidazolium hexa-,2 -acetato-acetatodiaqua-,3 -oxo-triiron(III) chloride dihydrate, (C4H7N2)[Fe3(C2H3O2)7O(H2O)2]Cl·2H2O, (II), with a trinuclear [Fe3(,3 -O)]7+ unit, are presented. Both structures are formed by two well differentiated entities, viz. a compact isolated cluster composed of FeIII ions coordinated to O2, and CH3CO2, anions, and an external group formed by a central Cl, ion surrounded by different solvent groups to which the anion is bound through hydrogen bonding. In the case of (I), charge balance cannot be achieved within the groups, so the structure is macroscopically ionic; in the case of (II), in contrast, each group is locally neutral owing to the internal compensation of charges. The trinuclear complex crystallizes with the metal cluster, chloride anion and 2-methylimidazolium cation bisected by a crystallographic mirror plane. [source] Do Trinuclear Triplesalen Complexes Exhibit Cooperative Effects?CHEMISTRY - A EUROPEAN JOURNAL, Issue 33 2010Characterization, Enantioselective Catalytic Sulfoxidation by Chiral Trinuclear FeIII Triplesalen Complexes, Synthesis Abstract The chiral triplesalen ligand H6chand provides three chiral salen ligand compartments in a meta -phenylene arrangement by a phloroglucinol backbone. The two diastereomeric versions H6chandRR and H6chandrac have been used to synthesize the enantiomerically pure chiral complex [(FeCl)3(chandRR)] (3RR) and the racemic complex [(FeCl)3(chandrac)] (3rac). The molecular structure of the free ligand H6chandrac exhibits at the terminal donor sides the O-protonated phenol,imine tautomer and at the central donor sides the N-protonated keto,enamine tautomer. The trinuclear complexes are comprised of five-coordinate square-pyramidal FeIII ions with a chloride at the axial positions. The crystal structure of 3rac exhibits collinear chiral channels of ,11,Å in diameter making up 33.6,% of the volume of the crystals, whereas the crystal structure of 3RR exhibits voids of 560,Å3. Mössbauer spectroscopy demonstrates the presence of FeIII high-spin ions. UV/Vis spectroscopy is in accordance with a large delocalized system in the central backbone evidenced by strong low-energy shifts of the imine ,,,* transitions relative to that of the terminal units. Magnetic measurements reveal weak intramolecular exchange interactions but strong magnetic anisotropies of the FeIII ions. Complexes 3rac and 3RR are good catalysts for the sulfoxidation of sulfides providing very good yields and high selectivities with 3RR being enantioselective. A comparison of 3RR and [FeCl(salen,)] provides higher yields and selectivities but lower enantiomeric excess values (ee values) for 3RR relative to [FeCl(salen,)]. The low ee values of 3RR appeared to be connected to a strong ligand folding in 3RR, opening access to the catalytically active high-valent Fe,O species. The higher selectivity is assigned to a cooperative stabilization of the catalytically active high-valent Fe,O species through the phloroglucinol backbone in the trinuclear complexes. [source] | ||||||||||