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Coordination Geometry (coordination + geometry)

Distribution by Scientific Domains
Chemistry98%
Distribution within Chemistry
Crystallography58%
General & Introductory Chemistry15%
6 Other Subdomains27%

Kinds of Coordination Geometry

  • octahedral coordination geometry
    		•
  • square-planar coordination geometry
    		•

    Selected Abstracts

    A [2]Rotaxane Flip Switch Driven by Coordination Geometry,

    ANGEWANDTE CHEMIE, Issue 29 2010
    Gregory
    Lieber das Zuckerbrot als die Peitsche! Eine Veränderung der Koordinationsgeometrie des Metalls in der terminalen Gruppe eines [2]Rotaxan-Liganden ergibt durch eine Reorientierung des eingeschlossenen Makrocyclus eine molekulare Schaltung. Der Schaltprozess konnte durch eine höhere Attraktivität der Koordinationsstelle hervorgerufen werden (quadratisch-planar), was jedoch durch eine verringerte Attraktivität der Koordinationsstelle nicht gelang (oktaedrisch). [source]

    Complexes of Yb3+ with EDTA and CDTA , Molecular and Electronic Structure

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 19 2008
    Janicki
    Abstract Two Yb3+ compounds, [C(NH2)3]2[Yb(EDTA)(H2O)2]ClO4·6H2O and [C(NH2)3][Yb(CDTA)(H2O)2]·4H2O, where EDTA is the ethylenediaminetetraacetate anion and CDTA is the trans -1,2-diaminecyclohexane- N,N,N,,N, -tetraacetate anion, were obtained and their crystal structures and spectroscopic properties were determined. In both compounds, the coordination geometries of the eight-coordinate Yb3+ ion are very similar. In each case, the inner sphere of the metal ion consists of four carboxyl oxygen atoms, two nitrogen atoms and two water molecules. The complexes were characterized by UV/Vis/NIR absorption at different temperatures and IR spectroscopy. The spectroscopic results revealed high sensitivity of the electronic 4f13 configuration upon minor changes in the coordination geometry around the Yb3+ ion. These data also demonstrate that species present in solutions of Yb3+,EDTA are similar to those found in the crystal, whereas in solutions of Yb3+,CDTA an equilibrium between at least two different forms exists. For the Yb3+,EDTA complex in solution and in the crystalline state, a charge-transfer transition was detected. Theoretical calculations revealed its complicated (Yb , ligand and ligand , Yb) character.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

    Copper-Binding Motifs: Structural and Theoretical Aspects

    HELVETICA CHIMICA ACTA, Issue 5 2003
    Amy Kaufman, Katz
    In this paper, we report the results of a study involving the coordination geometries of CuI, CuII, and CuIII crystal structures in the Cambridge Structural Database, and on Cu binding sites in proteins taken from the Protein Data Bank. The motifs used to bind two bridged Cu ions are also described. In addition, we report the results of ab initio molecular-orbital calculations performed on a variety of model CuI/CuII complexes (CuI/CuII,XnYm (X, Y=NH3, SH2); n+m=4; n=0,4) to provide data on the structural and energetic changes that occur in isolated complexes when the oxidation state of the Cu ion is changed from II to I while the coordination number is conserved. The use of such simple ligands in these calculations eliminates constraints on the geometric changes that may be imposed by more-complicated ligands. [source]

    Prediction of the crystal structures of perovskites using the software program SPuDS

    ACTA CRYSTALLOGRAPHICA SECTION B, Issue 6 2001
    Michael W. Lufaso
    The software program SPuDS has been developed to predict the crystal structures of perovskites, including those distorted by tilting of the octahedra. The user inputs the composition and SPuDS calculates the optimal structure in ten different Glazer tilt systems. This is performed by distorting the structure to minimize the global instability index, while maintaining rigid octahedra. The location of the A -site cation is chosen so as to maximize the symmetry of its coordination environment. In its current form SPuDS can handle up to four different A -site cations in the same structure, but only one octahedral ion. Structures predicted by SPuDS are compared with a number of previously determined structures to illustrate the accuracy of this approach. SPuDS is also used to examine the prospects for synthesizing new compounds in tilt systems with multiple A -site coordination geometries (a+a+a+, a0b+b+, a0b,c+). [source]

    [Cr8(PhCO2)16O4]·4CH3CN·2H2O: structural origin of magnetic anisotropy in a molecular spin cluster

    ACTA CRYSTALLOGRAPHICA SECTION C, Issue 9 2010
    John Fielden
    The Cr4O4 hetero-cubane-centered octachromium(III) cluster [Cr8(PhCO2)16O4] crystallizes from fluorobenzene,acetonitrile as dodeca-,2 -benzoato-tetrabenzoatotetra-,4 -oxido-octachromium(III) acetonitrile tetrasolvate dihydrate, [Cr8(C7H5O2)16O4]·4C2H3N·2H2O, (I). Crystals produced by this method are significantly more stable than the originally published dichloromethane pentasolvate, [Cr8(PhCO2)16O4]·5CH2Cl2 [Atkinson et al. (1999). Chem. Commun. pp. 285,286], leading to a significantly higher quality structure and allowing the production of large quantities of high-quality nondeuterated and deuterated material suitable for inelastic neutron scattering (INS) measurements. Compound (I) reveals a higher symmetry structure in which the cluster sits on a twofold rotation axis, and is based on an asymmetric unit containing four crystallographically independent Cr positions, two oxide ligands, eight benzoate ligands, two acetonitrile solvent molecules and one disordered water molecule. All the Cr atoms are six-coordinate, with an octahedral geometry for the inner cubane and a more highly distorted coordination environment in the outer positions. Despite the higher symmetry, the coordination geometries observed in (I) are largely similar to the dichloromethane pentasolvate structure, indicating that crystal-packing effects have little influence on the molecular structure of [Cr8(PhCO2)16O4]. Close structural analysis reveals that the high magnetic anisotropy observed in the INS measurements is a consequence of the distorted coordination geometry of the four outer Cr atoms. [source]

    Poly[bis(,4 -benzene-1,2-dicarboxylato)di-,3 -isonicotinato-dilanthanum(III)]

    ACTA CRYSTALLOGRAPHICA SECTION C, Issue 12 2009
    Guo-Ming Wang
    In the title compound, [La2(C8H4O4)2(C6H4NO2)2]n, there are two crystallographically independent La centres, both nine-coordinated in tricapped trigonal prismatic coordination geometries by eight carboxylate O atoms and one pyridyl N atom. The La centres are linked by the carboxylate groups of isonicotinate (IN,) and benzene-1,2-dicarboxylate (BDC2,) ligands to form La,carboxylate chains, which are further expanded into a three-dimensional framework with nanometre-sized channels by La,N bonds. In the construction of the resultant architecture, in tricapped trigonal prismatic coordination geometries by eight carboxylate O atoms and one pyridyl N atom, while the BDC ligands link to four different cations each, displaying penta- and heptadentate chelating,bridging modes, respectively. [source]

    Poly[[di-,-aqua-tetraaquadi-,-hydroxido-bis(,3 -3-nitrophthalato)tricopper(II)] dihydrate]

    ACTA CRYSTALLOGRAPHICA SECTION C, Issue 1 2009
    Feng-Qin Wang
    The novel title complex, {[Cu3(C8H3NO6)2(OH)2(H2O)6]·2H2O}n, has a one-dimensional polymeric double chain structure where the three Cu atoms are linked by ,2 -OH and ,2 -H2O groups, and these trinuclear centres are bridged by two 3-nitrophthalate ligands. The asymmetric unit contains one and a half crystallographically independent Cu atoms (one lying on a centre of inversion), both coordinated by six O atoms and exhibiting distorted octahedral coordination geometries, but with different coordination environments. Each 3-nitrophthalate ligand connects to three Cu atoms through two O atoms of one carboxylate group and one O atom of the nitro group. The remaining carboxylate group is free and is involved in intrachain hydrogen bonds, reinforcing the chain linkage. [source]

    A novel bridged asymmetric binuclear manganese(II) complex with DTPB [DTPB is 1,1,4,7,7-pentakis(1H -benz­imidazol-2-yl­methyl)-1,4,7-tri­aza­heptane]

    ACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2004
    Xu-Xiu Yan
    The crystal structure of the title compound, tetra­chloro­[,-1,1,4,7,7-pentakis(1H -benzimidazol-2-yl­methyl)-1,4,7-tri­azaheptane]­dimanganese(II) methanol pentasolvate tetrahydrate, [Mn2Cl4(C44H43N13)]·5CH4O·4H2O, contains an ­asymmetric dinuclear MnII,DTPB [DTPB is 1,1,4,7,7-pentakis(1H -benzimidazol-2-yl­methyl)-1,4,7-tri­aza­heptane] complex with an intra-ligand bridging group (,NCH2CH2N,), as well as several solvate mol­ecules (methanol and water). Both MnII cations have similar distorted octahedral coordination geometries. One MnII cation is coordinated by a Cl, anion and five N atoms from the ligand, and the other is coordinated by three Cl, anions and three N atoms of the same ligand. The Mn,Mn distance is 7.94,Å. A Cl,H,O,H,O,H,N hydrogen-bond chain is also observed, connecting the two parts of the complex. [source]

    Designed Topology and Site-Selective Metal Composition in Tetranuclear [MM,,,,M,M] Linear Complexes

    CHEMISTRY - A EUROPEAN JOURNAL, Issue 42 2009
    Leoní
    Abstract The ligand 1,3-bis[3-oxo-3-(2-hydroxyphenyl)propionyl]benzene (H4L), designed to align transition metals into tetranuclear linear molecules, reacts with MII salts (M=Ni, Co, Cu) to yield complexes with the expected [MM,,,MM] topology. The novel complexes [Co4L2(py)6] (2; py=pyridine) and [Na(py)2][Cu4L2(py)4](ClO4) (3) have been crystallographically characterised. The metal sites in complexes 2 and 3, together with previously characterised [Ni4L2(py)6] (1), favour different coordination geometries. These have been exploited for the deliberate synthesis of the heterometallic complex [Cu2Ni2L2(py)6] (4). Complexes 1, 2, 3 and 4 exhibit antiferromagnetic interactions between pairs of metals within each cluster, leading to S=0 spin ground states, except for the latter cluster, which features two quasi-independent S=1/2 moieties within the molecule. Complex 4 gathers the structural and physical conditions, thus allowing it to be considered as prototype of a two-qbit quantum gate. [source]

    Structural and Magnetic Resolution of a Two-Step Full Spin-Crossover Transition in a Dinuclear Iron(II) Pyridyl-Bridged Compound

    CHEMISTRY - A EUROPEAN JOURNAL, Issue 32 2006
    Jarrod J. M. Amoore
    Abstract A dinuclear iron(II) complex containing the new pyridyl bridging ligand, 2,5-di(2,,2,,-dipyridylamino)pyridine (ddpp) has been synthesised and characterised by single-crystal X-ray diffraction, magnetic susceptibility and Mössbauer spectral methods. This compound, [Fe2(ddpp)2(NCS)4],4,CH2Cl2, undergoes a two-step full spin crossover. Structural analysis at each of the three plateau temperatures has revealed a dinuclear molecule with spin states HS,HS, HS,LS and LS,LS (HS: high spin, LS: low spin) for the two iron(II) centres. This is the first time that resolution of the metal centres in a HS,LS ordered state has been achieved in a two-step dinuclear iron(II) spin-crossover compound. Thermogravimetric data show that the dichloromethane solvate molecules can be removed in two distinct steps at 120,°C and 200,°C. The partially de-solvated clathrate, [Fe2(ddpp)2(NCS)4],CH2Cl2, undergoes a one-step transition with an increased transition temperature with respect to the as synthesised material. Structural characterisation of this material reveals subtle changes to the coordination geometries at each of the iron(II) centres and striking changes to the local environment of the dinuclear complex. The fully de-solvated material remains high spin over all temperatures. Interestingly, the solvent can be re-introduced into the monosolvated solid to achieve complete conversion back to the original two-step crossover material, [Fe2(ddpp)2(NCS)4],4,CH2Cl2. [source]

    Two Cobalt Compounds Based on Azide/Methoxy and Isonicotinate N -Oxide Ligands Exhibiting Ferromagnetic and Antiferromagnetic Interactions

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 28 2010
    Fu-Chen Liu
    Abstract Two new CoII complexes, [Co(OCH3)L] (1) and [Co3(N3)4(OCH3)2L2] (2) (L = isonicotinate N -oxide), were synthesized by solvothermal reaction and magnetically characterized. The cobalt ions in 1 and 2 all exhibit distorted octahedral coordination geometry. In 1, there is a ,11 -methoxy/syn,syn -carboxylate mixed coordinated cobalt chain with mixed coordination, and a 3D structure is formed by the chains linked through the L ligands. In 2, the alternating CoII chains that are formed by linking the double end-on azide-bridged trimers are connected by the L ligands to form a 2D layer. Magnetic studies revealed that ferromagnetic coupling exists between the CoII ions in 1, and 1 undergoes a ferromagnetic transition at 2.5 K, whereas alternating ferromagnetic (FM) and antiferromagnetic (AFM) interactions exist in the chain of 2. [source]

    Macrocyclic Receptor Showing Improved PbII/ZnII and PbII/CaII Selectivities

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 17 2010
    Raquel Ferreirós-Martínez
    Abstract Herein we report on the macrocyclic receptor N,N,-bis[(6-carboxy-2-pyridyl)methyl]-1,10-diaza-15-crown-5 (H2bp15c5) and its coordination properties towards ZnII, CdII, PbII, and CaII. The stability constants of these complexes determined by pH-potentiometric titration at 25 °C in 0.1 M KNO3 vary in the following order: PbII > CdII >> ZnII > CaII. As a result, bp15c5 presents very important PbII/ZnII and PbII/CaII selectivities. These results are in contrast to those reported for the related receptor derived from 1,7-diaza-12-crown-4, which provides very similar complex stabilities for ZnII and PbII. The X-ray crystal structure of [Cd(Hbp15c5)]+ shows heptadentate binding of the ligand to the metal ion, with two oxygen atoms of the macrocyclic unit remaining uncoordinated. The 1H NMR spectra of the complexes formed with PbII, ZnII, and CaII (D2O) show very broad peaks in the region 2,5 ppm, indicating an important degree of flexibility of the crownmoiety in these complexes. On the contrary, the 1H and 13C NMR spectra recorded for the CdII complex are well resolved and could be fully assigned. A detailed conformational investigation using theoretical calculations performed at the DFT (B3LYP) level predict a minimum energy conformation for [Cd(bp15c5)] that is very similar to that observed in the solid state. Analogous calculations performed on the [M(bp15c5)] (M = Zn or Pb) systems predict hexadentate binding of the ligand to these metal ions. In the case of the PbII complex our calculations indicate that the 6s lone pair is stereochemically active, which results in a hemidirected coordination geometry around the metal ion. The minimum energy conformations calculated for the ZnII, CdII, and PbII complexes are compatible with the experimental NMR spectra obtained in D2O solution. [source]

    Complexes of Yb3+ with EDTA and CDTA , Molecular and Electronic Structure

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 19 2008
    Janicki
    Abstract Two Yb3+ compounds, [C(NH2)3]2[Yb(EDTA)(H2O)2]ClO4·6H2O and [C(NH2)3][Yb(CDTA)(H2O)2]·4H2O, where EDTA is the ethylenediaminetetraacetate anion and CDTA is the trans -1,2-diaminecyclohexane- N,N,N,,N, -tetraacetate anion, were obtained and their crystal structures and spectroscopic properties were determined. In both compounds, the coordination geometries of the eight-coordinate Yb3+ ion are very similar. In each case, the inner sphere of the metal ion consists of four carboxyl oxygen atoms, two nitrogen atoms and two water molecules. The complexes were characterized by UV/Vis/NIR absorption at different temperatures and IR spectroscopy. The spectroscopic results revealed high sensitivity of the electronic 4f13 configuration upon minor changes in the coordination geometry around the Yb3+ ion. These data also demonstrate that species present in solutions of Yb3+,EDTA are similar to those found in the crystal, whereas in solutions of Yb3+,CDTA an equilibrium between at least two different forms exists. For the Yb3+,EDTA complex in solution and in the crystalline state, a charge-transfer transition was detected. Theoretical calculations revealed its complicated (Yb , ligand and ligand , Yb) character.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

    Reactions of [Hg(Tab)2](PF6)2 [Tab = 4-(trimethylammonio)benzenethiolate] with NaX (X = Cl, NO2, NO3): Isolation and Structural Characterization of a Series of Mono- and Binuclear Hg/Tab/X Compounds

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 16 2008
    Xiao-Yan Tang
    Abstract The complex [Hg(Tab)2](PF6)2 [Tab = 4-(trimethylammonio)benzenethiolate] (1) reacts with one or two equivalents of NaCl to afford the mononuclear complex [Hg(Tab)2Cl](PF6) (2) and the dinuclear complex [{Hg(,-Tab)(Tab)Cl}2]Cl2·H2O (3·H2O), respectively. Similar reactions of 1 with NaCl and NaX (molar ratio = 1:1) produce the dinuclear species [{Hg(,-Tab)(Tab)Cl}2]X2 [X = NO2 (4), NO3 (5)], while those with NaNO2 or NaNO3 give rise to [{Hg(,-Tab)(Tab)X}2]X2 [X = NO2 (6), NO3 (7)]. Complexes 2,7 have been characterised by elemental analysis, IR, UV/Vis, and 1H NMR spectroscopy, and X-ray crystallography. The Hg atom of the [Hg(Tab)2Cl]+ cation in 2 adopts a T-shaped coordination geometry. Two [Hg(Tab)2Cl]+ cations in 3·H2O, 4, and 5 are linked by a pair of weak Hg,S bonds to form a dimeric [Hg(,-Tab)(Tab)Cl]22+ dication, and the centrosymmetric [Hg(,-Tab)(Tab)X]22+ dication in 6 and 7 consists of two [Hg(Tab)2X]+ cations linked by a couple of weak Hg,S bonds. The hydrogen-bonding interactions in 2,7 lead to the formation of interesting 2D (5, 7) or 3D (2,4, 6) hydrogen-bonded networks.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

    Surprising Coordination Geometry Differences in CeIV - and PuIV -Maltol Complexes,

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 13 2008
    Géza Szigethy
    Abstract As part of a study to characterize the detailed coordination behavior of PuIV, single-crystal X-ray diffraction structures have been determined for PuIV and CeIV complexes with the naturally occurring ligand maltol (3-hydroxy-2-methylpyran-4-one) and its derivative bromomaltol (5-bromo-3-hydroxy-2-methylpyran-4-one). Although CeIV is generally accepted as a structural analog for PuIV, and the maltol complexes of these two metals are isostructural, the corresponding bromomaltol complexes are strikingly different with respect to ligand orientation about the metal ion: All complexes exhibit trigonal dodecahedral coordination geometry but the CeIV,bromomaltol complex displays an uncommon ligand arrangement not found in the PuIV complex.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

    Reductive Activation of tripod Metal Compounds: Identification of Intermediates and Preparative Application,

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 9 2008
    Jürgen Mautz
    Abstract [tripodCoCl2] {tripod = CH3C(CH2PPh2)3} when treated with KC8 in THF solution under an argon atmosphere produces a reactive species ["tripodCo0"] (A) which undergoes oxidative additions with stannanes, [tripodCo(H)2(SnBu3)] (4), formed, for example, by addition of Bu3SnH. Silanes, R3SiH, undergo the same type of reaction producing [tripodCo(H)2(SiR3)] (R = Et: 5a; R = Ph: 5b). The solid-state structures of all the compounds [tripodCo(H)2(ER3)] (E = Si, R = Ph; E = Sn, R = Ph, Bu) are rather similar. While they contain six-coordinate cobalt with the formal oxidation state of cobalt being +III the coordination geometry is not octahedral: the heteroelement E deviates from the position which it would have in octahedral coordination by around 40° while the other five ligands, three phosphorus and two hydrogen, have the expected interligand angles of around 90° and 180°, respectively. The deviation of the heteroelement E is such that it approaches the metal bonded hydrogen atoms leading to short H···E contacts of only about 190 pm (E = Si) and 230 pm (E = Sn), respectively. The generation of a reactive species ["tripodCo0"] (A) was transferred to the synthesis of a reactive tripodnickel(0) species by treating a THF solution of [(DME)NiBr2] with KC8 in the presence of tripod. This species reacts with two electron donor ligands L to produce the pseudo tetrahedral compounds [tripodNi(L)] {L = PPh3 (6), AsPh3 (7), cHexNC (8), tBuNC (9), C2H4 (10)}. The identity of the reactive nickel(0) species as unequivocally deduced from NMR experiments is [tripod4Ni3] (12). All compounds were characterised by the usual analytic techniques including X-ray analysis where applicable.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

    Synthesis and Crystal Structure of a Heptanuclear and an Octanuclear Copper(II) Complex Derived from ,- D -Glucofuranoses

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 23 2007
    Michael Gottschaldt
    Abstract CuII complexes of different 6-(,-keto-enamino)-6-deoxy-1,2- O -isopropylidene-,- D -glucofuranoses 3a,f have a high tendency to build up oligonuclear clusters. Two new oligonuclear copper(II) complexes could be synthesised, crystallised and their structures determined. The complex Cu(3a) was found to consist of a heptanuclear cluster in which two ,-cubane like substructures share one copper ion. The structure is highly asymmetric and in the cluster every CuII ion has a different coordination geometry. Variation of the residues of the ,-ketoenaminic unit leads to the formation of the octanuclear copper(II) complex Cu(3e). Similarly, this has two ,-cubane subunits consisting of a heptanuclear structure with an additionally attached copper ion. In the crystal, two Cu8 cluster molecules are found differing in their geometries due to intermolecular interactions responsible for the formation of a supramolecular network. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

    Efficient DNA Cleavage Induced by Copper(II) Complexes of Hydrolysis Derivatives of 2,4,6-Tri(2-pyridyl)-1,3,5-triazine in the Presence of Reducing Agents

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 6 2007
    Joaquín Borrás
    Abstract The reaction of 2,4,6-tri(pyridyl)-1,3,5-triazine (ptz) and copper(II) salts in dmf/water (1:1) results in the hydrolysis of ptz and formation of the anions bis(2-pyridylcarbonyl)amide (ptO2,) and bis(2-pyridylamine)amide (ptN2,), which are found in the complexes [Cu(ptN2)(OAc)]·3H2O (1), [Cu(ptO2)(OAc)(H2O)]·H2O (2), [Cu(ptN2)(for)]·3H2O (3) (for = formate), [Cu(ptO2)(for)(H2O)] (4), [Cu(ptO2)(benz)]·H2O (5) (benz = benzoate), and [Cu(ptO2)F(H2O)]2·3H2O (6). This report includes the chemical and spectroscopic characterization of all these complexes along with the crystal structures of 4,6. The coordination spheres of CuII in 4 and 5 are best described as distorted tetragonal square pyramidal for the former and distorted square planar for the latter. The crystal structure of 6 shows the presence of two discrete monomeric [Cu(ptO2)F(H2O)] entities in the crystallographic asymmetric unit in which both copper(II) ions have a distorted square-pyramidal coordination geometry. The binding of the complexes to DNA has been investigated with the aid of viscosity and thermal denaturation studies, both of which indicate that the interaction is probably due to the outer-sphere mechanism. The ability of the compounds to cleave DNA has also been tested. Efficient oxidative cleavage was observed in the presence of a mild reducing agent (ascorbate) and dioxygen. Mechanistic studies with reactive oxygen species (ROS) scavengers confirm that hydrogen peroxide, the hydroxyl radical, singlet oxygen-like species, and the superoxide anion are necessary diffusible intermediates in the scission process. A mechanism involving either the Fenton or theHaber,Weiss reaction plus the formation of copper oxene species is proposed for the DNA cleavage mediated by these compounds.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

    Anion-Dependent Structural Diversity in Silver(I) Complexes of 4-Amino-3,5-diisopropyl-1,2,4-triazole

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 5 2007
    Guang Yang
    Abstract Reactions of silver salts with 4-amino-3,5-diisopropyl-1,2,4-triazole (L) afford dinuclear complex [Ag2L2(NO3)2(CH3CN)], triangular complex [Ag3L3](CF3SO3)3, and cyclic tetranuclear complexes [Ag4L6](BF4)4 and [Ag4L6](ClO4)4. On the basis of the X-ray analyses, anions are found to play an important role in determining the structures. Through coordination/noncoordination, anions can impart their influence on the coordination geometry of Ag atoms and the angles of N,Ag,N, which seems to be the main factor controlling the nuclearity of the reaction products in this system. 1H NMR and MS measurements suggest that these complexes probably retain their structural integrities in CH3CN solution. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

    Chelate [2-(Iminoethyl)pyridine N -oxide]metal Complexes , Synthesis and Structural Comparison with Their Chemically Related 2-(Iminoethyl)pyridine-Derived Systems

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 2 2006
    Katrin Nienkemper
    Abstract The N,O-chelate ligands 2-(iminoethyl)pyridine N -oxide (2a) and 2-(iminoethyl)-6-isopropylpyridine N -oxide (2b) were prepared by conventional synthetic routes, the latter involving a variant of the Reissert,Henze reaction. Treatment of 2a with FeCl2 resulted in a deoxygenation reaction of the ligand and formation of the salt [bis{2-(iminoethyl)pyridine}FeCl]+[FeCl4], (18a). In contrast, the reaction of 2a with PdCl2 or CoCl2 cleanly furnished the six-membered chelate [,N,O -2(iminoethyl)pyridine N -oxide]MCl2 complexes (19a, M = Pd) or (20a, M = Co), respectively, which were both characterised by X-ray diffraction. Treatment of 2b with [NiBr2(dme)], followed by crystallisation from THF, gave the complex [(,N,O - 2b)NiBr2(THF)] (21b), which features a distorted trigonal-bipyramidal coordination geometry of the central metal atom. The reaction of 2a with [NiBr2(dme)] gave the structurally related complex [(,N,O - 2a)NiBr2(,O - 2a)] (21a). The N,O-chelate Pd complex 19a was shown to be an active catalyst for the Suzuki coupling reaction. The ligand systems 2a,b and their related 2-(iminoethyl)pyridines 3a,b and a variety of metal complexes of ligands 3 were also prepared and characterised for comparison by X-ray diffraction. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

    Reaction of Mercury(0) with the I2 Adduct of Tetraphenyldithioimidodiphosphinic Acid (SPPh2)2NH (HL) , Crystal Structures of [Hg(HL)I2] and HgL2

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 23 2004
    M. Carla Aragoni
    Abstract The complex [Hg(HL)I2] (1) has been synthesised by reacting liquid Hg(0) in Et2O under mild reaction conditions with the I2 adduct of HL, HL·I2, while HgL2 (2) has been obtained from the reaction of compound 1 with HL in CH3CN. A single-crystal X-ray investigation of 1 shows four independent molecules in the asymmetric unit, each of which contains an HgII ion coordinated to two iodine atoms and two sulfur atoms of one bidentate neutral ligand in a distorted tetrahedral coordination geometry. Compound 2 consists of two anionic ligands coordinated to an HgII ion, which again displays a distorted tetrahedral coordination sphere. The reaction of 2 with HI (55 wt.-% in water) affords [Hg(HL)2](I)2 (3). Compounds 1, 2, and 3 have been characterised by FT-IR and 31P NMR spectroscopy. Density functional calculations suggest that compound 3 should feature a distorted tetrahedral coordination around the metal centre, with unequal Hg,S bond lengths. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

    Electroactive Films of Multicomponent Building Blocks,

    ADVANCED FUNCTIONAL MATERIALS, Issue 5 2007
    I. Yildiz
    Abstract A ligand consisting of a 2,2,-bipyridine core and two 4,4,-bipyridinium arms terminated by a thiol group is prepared following a multistep synthetic procedure. Two of these ligands assemble around a single CuI center as a result of the tetrahedral coordination of their 2,2,-bipyridine cores by the metal. Both the ligand and the complex adsorb spontaneously on the surface of polycrystalline-gold electrodes. The surface coverage of the films prepared by immersing a gold substrate into a solution of the ligand increases from monolayer to multilayer values with immersion time. Instead, the complex can only form monolayers. The cyclic voltammograms of the resulting films show the characteristic response for the reversible reduction of the 4,4,-bipyridinium dications to their radical cations. In the case of the complex, a wave for the monoelectronic oxidation of the metal center can also be observed. The back reduction wave, however, is markedly broader and appears at significantly lower potentials. Model studies in solution indicate that this response is a result of the presence of free thiol groups and is consistent with a change in the coordination geometry of the metal. Specifically, the oxidation of the CuI center to a CuII ion is, presumably, accompanied by the folding of one of the thiol groups back to interact with the metal. Thus, oxidation/reduction cycles of the metal center can, in principle, be exploited to control reversibly large amplitude molecular motions at the electrode/solution interface in the shape of the folding/unfolding of oligomethylene chains. [source]

    Synthesis, characterization, and in vitro antimicrobial activities of organotin(IV) complexes of Schiff bases with ONO-type donor atoms

    HETEROATOM CHEMISTRY, Issue 6 2010
    Gülgün Yeni, ehirli
    A new series of diorganotin complexes of the type R2SnL (L1: N -(2-hydroxy-5-chlorophenyl)- 3-ethoxysalicylideneimine, R = Me, (Me2SnL1), R = n -Bu, (n -Bu2SnL1), R = Ph, (Ph2SnL1), L2: N -(2-hydroxy-4-nitro-5-chlorophenyl)-3-ethoxysalicylideneimine, R = Ph, Ph2SnL2, L3: N -(2-hydroxy-4-nitrophenyl)-3-methoxysalicylideneimine, R = Me, (Me2SnL3), R = n -Bu, (n -Bu2SnL3), L4: N -(2-hydroxy-4-nitrophenyl)-3-ethoxysalicylideneimine, R = Me, (Me2SnL4), R = n -Bu, (n -Bu2SnL4)) were synthesized and characterized by elemental analysis, infrared (IR), 1H, and 13C NMR mass spectroscopic techniques, and electrochemical measurements. Ph2SnL1 and Ph2SnL2 were also characterized by X-ray diffraction analysis and were found to show a fivefold C2NO2 coordination geometry nearly halfway between a trigonal bipyramidal and distorted square pyramidal arrangement. The CSnC angles in the complexes were calculated using Lockhart's equations with the 1J(117/119Sn- 13C) and 2J(117/119Sn- 1H) values from the 1H NMR and 13C NMR spectra. Biocidal activity tests against several micro-organisms and some fungi indicate that all the complexes are mildly active against Gram (+) bacteria and the fungi, A. niger and inactive against Gram (,) bacteria. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:373,385, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/hc.20628 [source]

    Stable conformations of 12-crown-O3N and its Li+ complex in aqueous solution

    JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 13 2002
    Kenzi Hori
    Abstract Stable conformations of 12-crown-O3N and its Li complexes in aqueous solution were investigated. To calculate the free energy differences of conformers of 12-crown-O3N and its Li+ complex, our procedure was to make use of two programs, CONFLEX and BOSS. The former generates conformers, and the latter calculates the differences in free energy of solvation between two conformers in aqueous solution. It was confirmed that the present procedure is applicable in solving the question of what is the most stable conformation of 12-crown-O3N in aqueous solution. Results of the calculations suggest that the order of stability for conformers in a vacuum is different from that in aqueous solution. It was also confirmed that the coordination geometry of solvent waters to Li+ changes depending on the distance between the cation and the crown ring. © 2002 Wiley Periodicals, Inc. J Comput Chem 23: 1226,1235, 2002 [source]

    Crystal structure of the antibiotic albomycin in complex with the outer membrane transporter FhuA

    PROTEIN SCIENCE, Issue 5 2000
    Andrew D. Ferguson
    Abstract One alternative method for drug delivery involves the use of siderophore-antibiotic conjugates. These compounds represent a specific means by which potent antimicrobial agents, covalently linked to iron-chelating siderophores, can be actively transported across the outer membrane of Gram-negative bacteria. These "Trojan Horse" antibiotics may prove useful as an efficient means to combat multi-drug,resistant bacterial infections. Here we present the crystallo-graphic structures of the natural siderophore-antibiotic conjugate albomycin and the siderophore phenylferricrocin, in complex with the active outer membrane transporter FhuA from Escherichia coli. To our knowledge, this represents the first structure of an antibiotic bound to its cognate transporter. Albomycins are broad-host range antibiotics that consist of a hydroxamate-type iron-chelating siderophore, and an antibiotically active, thioribosyl pyrimidine moiety. As observed with other hydroxamate-type siderophores, the three-dimensional structure of albomycin reveals an identical coordination geometry surrounding the ferric iron atom. Unexpectedly, this antibiotic assumes two conformational isomers in the binding site of FhuA, an extended and a compact form. The structural information derived from this study provides novel insights into the diverse array of antibiotic moieties that can be linked to the distal portion of iron-chelating siderophores and offers a structural platform for the rational design of hydroxamate-type siderophore-antibiotic conjugates. [source]

    Change in electronic structure in a six-coordinate copper(II) complex accompanied by an anion order/disorder transition

    ACTA CRYSTALLOGRAPHICA SECTION B, Issue 2 2010
    Colin A. Kilner
    A variable-temperature crystallographic study of [Cu(LOH)2][ClO4]2·2(CH3)2CO [LOH = 2,6-bis(hydroxyiminomethyl)pyridine] between 30 and 300,K is presented. The complex exhibits an unusual electronic structure at room temperature with a {}1 ground state, corresponding to an axially compressed ligand coordination geometry about the copper ion. This reflects a suppression of the pseudo-Jahn,Teller distortion that is normally shown by copper(II) compounds with this ligand geometry [Halcrow et al. (2004). New J. Chem.28, 228,233]. On cooling the compound undergoes an abrupt structural change at 157,±,3,K, that does not involve a change in the space group (P), but causes significant changes to c and the unit-cell angles. This reflects a conformational rearrangement of the complex dication, towards a more typical pseudo-Jahn,Teller elongated coordination geometry. This occurs concurrently with a crystallographic ordering of one of the two perchlorate anions, and a significant displacement of the two lattice acetone molecules. The transformation involves displacements of up to 0.5,Å in the non-H atoms of the structure at 30,K, compared with their positions at 300,K. The change in coordination geometry of the complex around 157,K is reflected in a small reduction in its magnetic moment near that temperature. [source]

    Using cluster analysis to study transition-metal geometries: four-coordinate complexes with two salicylaldiminato or related ligands

    ACTA CRYSTALLOGRAPHICA SECTION B, Issue 4 2007
    Andrew Parkin
    Cluster analysis is shown to be an effective method to analyse and classify metal coordination geometry in a very large number of four-coordinate bis -salicylaldimato (or bis- ,-iminoketonate) transition-metal complexes available in the Cambridge Structural Database. The methods described require no prior knowledge of chemistry to be input; retrieved structures are automatically clustered into groups based purely on the geometric similarity of the fragments and these groupings can then be interpreted by the structural chemist. [source]

    [Cr8(PhCO2)16O4]·4CH3CN·2H2O: structural origin of magnetic anisotropy in a molecular spin cluster

    ACTA CRYSTALLOGRAPHICA SECTION C, Issue 9 2010
    John Fielden
    The Cr4O4 hetero-cubane-centered octachromium(III) cluster [Cr8(PhCO2)16O4] crystallizes from fluorobenzene,acetonitrile as dodeca-,2 -benzoato-tetrabenzoatotetra-,4 -oxido-octachromium(III) acetonitrile tetrasolvate dihydrate, [Cr8(C7H5O2)16O4]·4C2H3N·2H2O, (I). Crystals produced by this method are significantly more stable than the originally published dichloromethane pentasolvate, [Cr8(PhCO2)16O4]·5CH2Cl2 [Atkinson et al. (1999). Chem. Commun. pp. 285,286], leading to a significantly higher quality structure and allowing the production of large quantities of high-quality nondeuterated and deuterated material suitable for inelastic neutron scattering (INS) measurements. Compound (I) reveals a higher symmetry structure in which the cluster sits on a twofold rotation axis, and is based on an asymmetric unit containing four crystallographically independent Cr positions, two oxide ligands, eight benzoate ligands, two acetonitrile solvent molecules and one disordered water molecule. All the Cr atoms are six-coordinate, with an octahedral geometry for the inner cubane and a more highly distorted coordination environment in the outer positions. Despite the higher symmetry, the coordination geometries observed in (I) are largely similar to the dichloromethane pentasolvate structure, indicating that crystal-packing effects have little influence on the molecular structure of [Cr8(PhCO2)16O4]. Close structural analysis reveals that the high magnetic anisotropy observed in the INS measurements is a consequence of the distorted coordination geometry of the four outer Cr atoms. [source]

    Two cobalt(III) mono-dimethylglyoximates isolated from one reaction

    ACTA CRYSTALLOGRAPHICA SECTION C, Issue 9 2010
    Agnieszka Czapik
    The reaction of cobalt(II) nitrate hexahydrate with dimethylglyoxime (DMGH2) and 1,10-phenanthroline (phen) in a 1:1:2 molar ratio results in two CoIII mono-dimethylglyoximates having two chelating phen ligands in cis positions and the CoIII atom coordinated by six N atoms in a distorted octahedral coordination geometry. The isolated products differ in the deprotonation state of the DMGH2 ligand. In [,-hydrogen bis(N,N,-dioxidobutane-2,3-diimine)]tetrakis(1,10-phenanthroline)cobalt(III) trinitrate ethanol disolvate 1.87-hydrate, [Co2(C4H6N2O2)(C4H7N2O2)(C12H8N2)4](NO3)3·2C2H6O·1.87H2O, (I), the C2 -symmetric cation is formed with the coordination [Co(DMG)(phen)2]+ cations aggregating via a very strong O,...H+...O, hydrogen bond with an O...O distance of 2.409,(4),Å. Crystals of (I) exhibit extensive disorder of the solvent molecules, the nitrate anions and one of the phen ligands. Compound (I) is a kinetic product, not isolated previously from similar systems, that transforms slowly into (N -hydroxy- N,-oxidobutane-2,3-diimine)bis(1,10-phenanthroline)cobalt(III) dinitrate ethanol monosolvate 0.4-hydrate, [Co(C4H7N2O2)(C12H8N2)2](NO3)2·C2H6O·0.40H2O, (II), with the DMGH, ligand hydrogen bonded to one of the nitrate anions. In (II), the solvent molecules and one of the nitrate anions are disordered. [source]

    Poly[aqua(,2 -benzene-1,4-dicarboxylato)(,2 -4,4,-bipyridine N,N,-dioxide)cadmium(II)], a threefold interpenetrating diamond net

    ACTA CRYSTALLOGRAPHICA SECTION C, Issue 8 2010
    Guohai Xu
    In the title compound, [Cd(C8H4O4)(C10H8N2O2)(H2O)]n, (I), each CdII atom is seven-coordinated in a distorted monocapped trigonal prismatic coordination geometry, surrounded by four carboxylate O atoms from two different benzene-1,4-dicarboxylate (1,4-bdc) anions, two O atoms from two distinct 4,4,-bipyridine N,N,-dioxide (bpdo) ligands and one water O atom. The CdII atom and the water O atom are on a twofold rotation axis. The bpdo and 1,4-bdc ligands are on centers of inversion. Each crystallographically unique CdII center is bridged by the 1,4-bdc dianions and bpdo ligands to give a three-dimensional diamond framework containing large adamantanoid cages. Three identical such nets are interlocked with each other, thus directly leading to the formation of a threefold interpenetrated three-dimensional diamond architecture. To the best of our knowledge, (I) is the first example of a threefold interpenetrating diamond net based on both bpdo and carboxylate ligands. There are strong linear O,H...O hydrogen bonds between the water molecules and carboxylate O atoms within different diamond nets. Each diamond net is hydrogen bonded to its two neighbors through these hydrogen bonds, which further consolidates the threefold interpenetrating diamond framework. [source]