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Distorted Square-planar Geometry (distorted + square-planar_geometry)

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Chemistry100%

Selected Abstracts

Design of Neutral Metallomesogens from 5,5-Dimethyldipyrromethane: Metal Ion Mediated Control of Folding and Hairpin Structures

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 32 2008
Kelly A. Ames
Abstract New ligands derived from 5,5-dimethyldipyrromethane and their corresponding neutral complexes with ZnII and PdII are described. The ligands incorporate either a hexacatenar [H2(1n), n = 1, 10, 12, 14 and 16], tetracatenar [H2(2n), n = 1 and 16] or an extended dicatenar structure [H2(3n), n = 1and 16]. Single-crystal X-ray structure determinations of [Zn2(11)2] and [Zn2(31)2] confirm a distorted tetrahedral geometry at ZnII to afford double-stranded helical structures, while the PdII species [Pd(31)] shows a distorted square-planar geometry with the ligand adopting an alternative hairpin conformation. The metal-free hexacatenar ligands H2(1n) (n = 10, 12, 14, 16) and the corresponding complexes [Zn2(116)2] and [Pd(1n)] (n = 12, 14, 16) are not mesomorphic. However, the tetracatenar complex [Zn2(216)2] generates a smectic mesophase, as confirmed by X-ray diffraction, while [Pd(216)] and the metal-free ligand H2(216) show no mesomorphic behaviour. Two of the extended dicatenar compounds, H2(316) and [Zn2(316)2] are non-mesomorphic, while [Pd(316)] displays a smectic A phase.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

Water-Soluble Sal2en- and Reduced Sal2en-Type Ligands: Study of Their CuII and NiII Complexes in the Solid State and in Solution

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 14 2006
Isabel Correia
Abstract The CuII and NiII complexes of the Schiff base pyr2en [N,N, -ethylenebis(pyridoxyliminato)] and reduced Schiff bases Rpyr2en [N,N, -ethylenebis(pyridoxylaminato)] and R(SO3,sal)2en (SO3,sal = salicylaldehyde-5-sulfonate) were prepared and characterized by elemental analysis, IR, UV/Vis, and EPR spectroscopy. The structure of Ni(pyr2en)·3H2O was determined by single-crystal X-ray diffraction. The pyr2en2, ligand is coordinated through two phenolate-O and imine-N atoms, in a distorted square-planar geometry. The complexation of CuII and NiII with Rpyr2en in aqueous solution is studied by pH-potentiometry, UV/Vis spectroscopy, as well as by EPR spectroscopy for the CuII system, and 1H NMR spectroscopy for the NiII system. Complex formation constants were determined and binding modes proposed. While for the CuII system all complexes present a 1:1 stoichiometry with different protonation states, for the NiII system the 2:1 (L/M) complexes become important in the basic pH range at a higher ligand excess. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

Synthesis and Binding Properties of Dendritic Oxybathophenanthroline Ligands towards Copper(II)

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 22 2005
Holger Stephan
Abstract Dendritic oxybathophenanthroline ligands (generation 0 to 3) have been synthesized by treatment of 4,7-bis(4,-hydroxyphenyl)-1,10-phenanthroline with the corresponding Fréchet-type dendrons carrying a benzylic bromide function at the focal point. The complexation of copper(II) has been studied by liquid,liquid extraction using the radioisotope 64Cu and time-resolved laser-induced fluorescence spectroscopy (TRLFS) in organic media indicating the formation of 1:3 complexes (Cu:dendritic ligand). Electronic and EPR spectroscopy were used to characterize the copper(II) chromophore, which is shown to have the expected distorted square-planar geometry with two phenanthroline donors coordinated to the copper(II) center. The third dendritic ligand therefore is proposed to be bound by secondary interactions. The stability constants of the 1:3 complexes were found to be in the order of log K , 16 in CHCl3. On the other hand, increasing generation of the dendritic Fréchet-type branches leads to enhanced shielding of the copper ion from the environment. Additional information about this behaviour was obtained by the fluorescence lifetimes, which are much less influenced upon addition of copper(II) salt to solutions of the higher generation ligands. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

Structural Characterization and a New One-Pot Synthesis of trans -Chloro(phenyl)bis(triphenylphosphane)nickel(II)

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 9 2003
Alexander Zeller
Abstract trans -[NiCl(Ph)(PPh3)2], the organometallic precursor for a new class of neutral polymerization catalysts, has been synthesized via a new synthetic route. The previously used alkylaluminum compounds are replaced by zinc dust for the reduction of the nickel(II) salt in the presence of triphenylphosphane forming the intermediate Ni(PPh3)4. In a one-pot reaction, chlorobenzene then adds oxidatively to the intermediate to form the title compound, which was structurally characterized, in high yields. Its geometry is compared to known structures of the higher homologues of group 10. All complexes adopt a distorted square-planar geometry, but the parent structure shows significantly shorter metal-ligand bond lengths than its Pd and Pt congeners, as expected. Density functional theory calculations (B3LYP/6,31G*) on the full structure are in very good agreement with the solid-state structure. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]

catena -Poly­[bis­[(2,2-bi­pyridine-,2N,N,)­copper(II)]-,4 -1,2,4,5-benzene­tetra­carboxyl­ato-,4O1:O2:O3:O4]

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 2 2004
Hong-Ping Xiao
In the title complex, [Cu2(C10H2O8)(C10H8N2)2]n, the CuII cation has a four-coordinated environment, completed by two carboxyl O atoms belonging to two 1,2,4,5-benzene­tetra­carboxyl­ate anions (TCB4,) and two N atoms from one 2,2,-bi­pyridine (2,2,-bipy) ligand, forming a distorted square-planar geometry. The [Cu(2,2,-bipy)]2+ moieties are bridged by TCB4, anions, which lie about inversion centres, forming an infinite one-dimensional coordination polymer with a double-chain structure along the a axis. A two-dimensional network structure is formed via a face-to-face ,,, interaction between the 2,2,-bipy rings belonging to two adjacent double chains, at a distance of approximately 3.56,Å. [source]