Transition-metal Ions (transition-metal + ion)

Distribution by Scientific Domains

Selected Abstracts

Enantiospecific Syntheses of Copper Cubanes, Double-Stranded Copper/Palladium Helicates, and a (Dilithium),Dinickel Coronate from Enantiomerically Pure Bis-1,3-diketones,Solid-State Self-Organization Towards Wirelike Copper/Palladium Strands,


Abstract Enantiomerically pure, vicinal diols 1 afforded in a two-step synthesis (etherification and subsequent Claisen condensation) chiral bis-1,3-diketones H2L(S,S) (3,a,c) with different substitution patterns. Reaction of these C2 -symmetric ligands with various transition-metal acetates in the presence of alkali ions generated distinct polynuclear aggregates 4,8 by diastereoselective self-assembly. Starting from copper(II) acetate monohydrate and depending on the ratio of transition-metal ion to alkali ion to ligand, chiral tetranuclear copper(II) cubanes (C,C,C,C)-[Cu4(L(S,S))2(OMe)4] (4,a,c) or dinuclear copper(II) helicates (P)-[Cu2(L(S,S))2] (5) could be synthesized with square-pyramidal and square-planar coordination geometry at the metal center. In analogy to the last case, with palladium(II) acetate double-stranded helical systems (P)-[Pd2(L(S,S))2] (6,7) were accessible exhibiting a linear self-organization of ligand-isolated palladium filaments in the solid state with short inter- and intramolecular metal distances. Finally, the introduction of hexacoordinate nickel(II) in combination with lithium hydroxide monohydrate and chiral ligand H2L(S,S) (3,a) allowed the isolation of enantiomerically pure dinuclear nickel(II) coronate [(Li,MeOH)2,{(,,,)-Ni2(L(S,S))2(OMe)2}] (8) with two lithium ions in the voids, defined by the oxygen donors in the ligand backbone. The high diastereoselectivity, induced by the chiral ligands, during the self-assembly process in the systems 4,8 could be exemplarily proven by circular dichroism spectroscopy for the synthesized enantiomers of the chiral copper(II) cubane 4,a and palladium(II) helicate 6. [source]

Synthesis, Structural, Thermal and Magnetic Characterization of a Pyrophosphato-Bridged Cobalt(II) Complex

Oluwatayo F. Ikotun
Abstract The reaction in water of CoII sulfate heptahydrate with 1,10-phenanthroline (phen) and sodium pyrophosphate (Na4P2O7) in a 2:4:1 stoichiometric ratio resulted in the crystallization of a neutral dinuclear CoII complex, {[Co(phen)2]2(,-P2O7)}6MeOH (1), as revealed by a single-crystal X-ray diffraction study. The bridging pyrophosphato ligand between the two [Co(phen)2]2+ units in a bis(bidentate) coordination mode places the adjacent metal centers at 4.857 distance, and its conformation gives rise to intramolecular ,,, stacking interaction between adjacent phen ligands. Indeed, intermolecular ,,, stacking interactions between phen ligands from adjacent dinuclear complexes create a supramolecular 2D network in 1. Magnetic susceptibility measurements on a polycrystalline sample of 1 in the temperature range 1.9,295 K are typical of an overall antiferromagnetic coupling with a maximum of the magnetic susceptibility at 3.0 K. The analysis of the magnetic data in the whole temperature range allows the determination of the value of the intramolecular magnetic coupling (J = ,1.23 cm,1). The ability of the pyrophosphato ligand to mediate magnetic interactions between different first-row transition-metal ions when adopting the bis(bidentate) bridging mode is analyzed and discussed in the light of the small number of magneto-structural reports on this type of compound, bearing in mind the number of unpaired electrons and type of magnetic orbitals on each metal center. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

Guest-Inclusion Behavior of Double-Strand 1D Coordination Polymers Based on N,N, -Type Schiff Base Ligands

Qing Wang
Abstract Four double-strand one-dimensional (1D) coordinationpolymers, namely, {[Ni(N3Py)2(NO3)2](C6H6)xC2H5OH}n (1), [Cd(ImBNN)2(CH3C6H4SO3)2]n (2), {[Co(N3OPy)2(H2O)2](ClO4)2C6H6H2O}n (3), and {[Co(N3OPy)2(H2O)2](ClO4)2(C8H10)x}n (4) were obtained from the assembly of three N,N, -type Schiff base ligands, 1,4-bis(3-pyridyl)-2,3-diaza-1,3-butadiene (N3Py), 2,5-bis(4,-(imidazol-1-yl)benzyl)-3,4-diaza-2,4-hexadiene (ImBNN), and bis[4-(3-pyridylmethylenemino)phenoxy]methane (N3OPy), with transition-metal ions. All complexes were characterized by single-crystal X-ray diffraction, X-ray powder diffraction, and FTIR measurements. The guest-inclusion behavior of these complexes were investigated by thermogravimetric and X-ray powder diffraction analyses. The structural relationship between the ligands and the cavity sizes and packing fashions have been discussed to elucidate the distinctive guest-inclusion behavior of these complexes.( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

Synthesis, Complexation and Spectrofluorometric Studies of a New NS3 Anthracene-Containing Macrocyclic Ligand

Abel Tamayo
Abstract A new fluorescent device for detecting protons and metal ions, 11-(9-anthracenylmethyl)-1,4,7-trithia-11-azacyclotetradecane (L), has been synthesised. In addition, the photophysical properties of both the free and protonated species have been examined by absorption and fluorescence titrations of dichloromethane solutions of L with methanesulfonic acid. The coordinating properties of L toward PdII, ZnII, NiII and CoII have been studied both in solution and in the solid state. Different behaviours have been observed in the absorption and fluorescence titrations of L with the above-mentioned transition-metal ions. To evaluate whether these differences were due to the existence of equilibria between protonated and complexed species, such titrations have been repeated in the presence of an equivalent amount of acid. The structure of the [Pd(L)](BF4)2 complex has been solved by X-ray crystallography. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

Effects of Transition-Metal Substitution on the Catalytic Properties of Barium Hexaaluminogallate

Toshiaki Yamaguchi
The effects of the substitution of transition-metal ions and/or reductant gases on the catalytic properties of barium hexaaluminogallate were investigated. Transition-metal-substituted hexaaluminogallates (BaM(Al,Ga)11O19, M = transition metal, Al/Ga = 9/3) were synthesized from aqueous metal nitrates and ammonium carbonate by the coprecipitation followed by crystallization at 1100C. The direct NOx reduction was observed over BaM(Al,Ga)11O19 to be around 10%. The NOx removal activity of BaM(Al,Ga)11O19 powders was improved by addition of C3H6 as a reductant gas. Co-, Ni- and Cu-substituted BaM(Al,Ga)11O19 catalysts exhibited about 40% NOx reduction with C3H6 in excess oxygen at a high space velocity of 10 000 h,1. The NOx reduction on Mn- and Fe-substituted BaM(Al,Ga)11O19 catalysts was less than 10% even in the presence of C3H6. The temperature of the effective NOx reduction on BaM(Al,Ga)11O19 catalysts could be adjusted from 350 to 500C by the selection of the transition-metal substitution in the catalysts. The catalysts hold high activities for NOx reduction even at 500C in water vapor produced in the combustion system of reductant gases. [source]

Inclusion of p -sulfonatothiacalix[4]arene and its metal complexes

Mingyan Wu
Abstract As a new member of the water-soluble calixarene family, p -sulfonatothiacalix[4]arene possesses unique properties resulting from its inherent structural characteristics. In our recent research, we have investigated the self-assembly of bowl-like p -sulfonatothiacalix[4]arenes with or without transition-metal ions in the presence of suitable guests. We have obtained a series of compounds with different structural motifs, such as capsules, tetranuclear clusters, and molecular clefts. In addition, p -sulfonatothiacalix[4]arenes show good inclusion abilities and can capture different guests by utilizing their hydrophobic cavities through supramolecular interactions. Even when a cone-like conformation is fixed, the p -sulfonatothiacalix[4]arene can also splay its opposite aromatic rings apart to adjust its cone-like conformations from C4v to C2v and even lower symmetries. All of these show that it is a good candidate for the research of inclusion phenomena. 2009 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 9: 155,168; 2009: Published online in Wiley InterScience ( DOI 10.1002/tcr.200800033 [source]

Syntheses, Structures, and Comprehensive NMR Spectroscopic Investigations of Hetero-Chalcogenidometallates: The Right Mix toward Multinary Complexes

Eugen Ruzin Dr.
Abstract Library of semiconductors: Mixtures of binary chalcogenidostannate anions in protic solution show statistic chalcogenide exchange (see scheme), which is examined by comprehensive NMR investigations, DFT calculations and chemical reactions. A simple approach is provided to generate a library of semiconductor compounds with finely tuned opto-electronic properties. Aqueous solutions of ternary ortho -chalcogenidostannate anions [SnE14,xE2x]4, (E1, E2=S, Se, Te) have been generated following different routes that all lead to equilibria of all possible permutations of binary and ternary anions. This has been rationalized by means of NMR studies that can be explained by calculations using density functional theory (DFT) methods. Thus, if one reacts such solutions with transition-metal ions, quaternary M/Sn/E1/E2 anions are obtained, which exhibit coordination by different ternary chalcogenidostannate ligands. The electronic excitation energies of the corresponding alkali metal salts lie between the Eg values of compounds containing either M/Sn/E1 or M/Sn/E2 anions. In this way, we provide a simple approach toward a library of semiconductor compounds with finely-tuned optoelectronic properties. [source]

Self-Assembly of [B -SbW9O33]9, Subunit with Transition Metal Ions (Mn2+, Cu2+, Co2+) in Aqueous Solution: Syntheses, Structures and Magnetic Properties of Sandwich Type Polyoxometalates with Subvalent SbIII Heteroatom

Jing-Ping Wang Prof.
Abstract Rational self-assembly of Sb2O3 and Na2WO4, or (NH4)18[NaSb9W21O86] with transition-metal ions (Mn2+, Cu2+, Co2+), in aqueous solution under controlled conditions yield a series of sandwich type complexes, namely, Na2H2[Mn2.5W1.5(H2O)8(B -,-SbW9O33)2],32,H2O (1), Na4H7[Na3(H2O)6Mn3(,-OAc)2(B -,-SbW9O33)2],20,H2O (OAc=acetate anion) (2), NaH8[Na2Cu4Cl(B -,-SbW9O33)2],21,H2O (3), Na8K[Na2K(H2O)2{Co(H2O)}3(B -,-SbW9O33)2], 10,H2O (4), and Na5H[{Co(H2O)2}3W(H2O)2(B -,-SbW9O33)2],11.5,H2O (5). These structures are determined by using the X-ray diffraction technique and further characterized by obtaining IR spectra and performing elemental analysis. Structure analysis reveals that polyoxoanions in 1 and 5 comprise of two [B -,-SbW9O33]9, building units, whereas 2, 3, and 4 consist of two isomerous [B -,-SbW9O33]9, building blocks, which are all linked by different transition-metal ions (Mn2+, Cu2+, or Co2+) with different quantitative nuclearity. It should be noted that compound 2 represents the first one-dimensional sinusoidal chain based on sandwich like tungstoantimonate building blocks through the carboxylate-bridging ligands. Additionally, 3 is constructed from sandwiched anions [Na2Cu4Cl(B -,-SbW9O33)2]9, linked to each other to form an infinitely extended 2D network, whereas 5 shows an interesting 3D framework built up from offset sandwich type polyoxoanion [{Co(H2O)2}3W(H2O)2(B -,-SbW9O33)2]6, linked by Co2+ and Na+ ions. EPR studies performed at 110,K and room temperature reveal that the metal cations (Mn2+, Cu2+, Co2+) reside in a square-pyramidal geometry in 2, 3, and 4. The magnetic behavior of 1,4 suggests the presence of weak antiferromagnetic coupling interactions between magnetic metal centers with the exchange integral J=,0.552,cm,1 in 2. [source]