The crystal and molecular structures of three copper-containing complexes and their activities in mimicking galactose oxidase

The structures of three copper-containing complexes, namely (benzoato-κ2 O,O′)[(E)-2-({[2-(diethylamino)ethyl]imino}methyl)phenolato-κ3 N,N′,O]copper(II) dihydrate, [Cu(C7H5O2)(C13H19N2O)]·2H2O, 1, [(E)-2-({[2-(diethylamino)ethyl]imino}methyl)phenolato-κ3 N,N′,O](2-phenylacetato-κ2 O,O′)copper(II), [Cu(C8H7O2)(C13H19N2O)], 2, and bis[μ-(E)-2-({[3-(diethylamino)propyl]imino}methyl)phenolato]-κ4 N,N′,O:O;κ4 O:N,N′,O-(μ-2-methylbenzoato-κ2 O:O′)copper(II) perchlorate, [Cu2(C8H7O2)(C12H17N2O)2]ClO4, 3, have been reported and all have been tested for their activity in the oxidation of D-galactose. The results suggest that, unlike the enzyme galactose oxidase, due to the precipitation of Cu2O, this reaction is not catalytic as would have been expected. The structures of 1 and 2 are monomeric, while 3 consists of a dimeric cation and a perchlorate anion [which is disordered over two orientations, with occupancies of 0.64 (4) and 0.36 (4)]. In all three structures, the central Cu atom is five-coordinated in a distorted square-pyramidal arrangment (τ parameter of 0.0932 for 1, 0.0888 for 2, and 0.142 and 0.248 for the two Cu centers in 3). In each species, the environment about the Cu atom is such that the vacant sixth position is open, with very little steric crowding.

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A Speculative Discussion of the Structural Details of 1-Bromo-2-iodo-benzenes

Zeitschrift für Naturforschung B ◽

10.1515/znb-2004-0304 ◽

2004 ◽

Vol 59 (3) ◽

pp. 264-268 ◽

Cited By ~ 3

Author(s):

Hubert Schmidbaur ◽

Oliver Minge ◽

Stefan Nogai

Keyword(s):

Single Crystal ◽

Van Der Waals ◽

Visible Region ◽

Molecular Structures ◽

X Ray Diffraction ◽

X Ray ◽

Crystal And Molecular Structures ◽

Structural Details ◽

Steric Crowding ◽

Speculative Discussion

The crystal and molecular structures of 2,4-dibromo-1-iodo-benzene (1) and 1,3-dibromo-2-iodobenzene (2) have been determined by single crystal X-ray diffraction. The proximity of two or three large halogen substituents (Br/I) induces only minor distortions of the C-C-Br/I angles (ca. 2°) and the halogen atoms remain in the plane of the molecules. These undistorted structures lead to short intramolecular, sub-van-der-Waals Br-I contacts [in the range 3.465(4) to 3.530(4) Å ]. The results suggest that the peripheral Br-I interactions have an attractive component which alleviates the repulsion out of steric crowding. The influence is associated with an absorption in the visible region and is possibly responsible for the enhanced reactivity of the 1,2-dihalobenzene molecules

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A Solvent-Dependent and Electrochemically Controlled Self-Assembling/Disassembling System

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc20031647 ◽

2003 ◽

Vol 68 (9) ◽

pp. 1647-1662 ◽

Cited By ~ 2

Author(s):

Valeria Amendola ◽

Massimo Boiocchi ◽

Yuri Diaz Fernandez ◽

Carlo Mangano ◽

Piersandro Pallavicini

Keyword(s):

Equilibrium Mixture ◽

Bidentate Ligand ◽

Molecular Structures ◽

The Self ◽

Molar Ratio ◽

Crystal And Molecular Structures ◽

Self Assembling ◽

Irreversible Oxidation ◽

Irreversible Reduction ◽

Metal Ligand

The bis-bidentate ligand R,S-1,2-diphenyl-N,N'-bis(2-quinolinemethylidene)ethane-1,2-diamine (ligand 4), containing two (iminomethyl)quinoline moieties separated by a cis-1,2-diphenylethylene spacer, forms stable complexes with both CuI and CuII. With CuII, the monomeric 1:1 complex [CuII(4)]2+ is obtained both in CH3CN and CH2Cl2. With CuI and overall 1:1 metal/ligand molar ratio, an equilibrium mixture is obtained in CH3CN, consisting of [CuI(4)2]+, [CuI2(4)2]2+ and [CuI2(4)(CH3CN)4]2+. The preponderant species is the two-metal one-ligand "open" complex [CuI2(4)(CH3CN)4]2+, in which each Cu+ cation is coordinated in a tetrahedral fashion by one (iminomethyl)quinoline unit and by two CH3CN molecules. Precipitation from the equilibrium mixture yields only crystals of [CuI2(4)(CH3CN)4](ClO4)2·2CH3CN, whose crystal and molecular structures have been determined. On the other hand, in the poorly coordinating CH2Cl2 solvent, only the dimeric helical [CuI2(4)2]2+ complex is obtained, when the overall metal/ligand 1:1 molar ratio is chosen. Addition of large quantities of acetonitrile to solutions of [CuI2(4)2]2+ in dichlorometane results in the formation of [CuI2(4)(CH3CN)4]2+, i.e. in the solvent-driven disassembling of the CuI helicate. While electrochemistry in CH3CN is poorly defined due to the presence of more than one CuI species, cyclic voltammetry experiments carried out in CH2Cl2 revealed a well defined behavior, with irreversible oxidation of [CuI2(4)2]2+ and irreversible reduction of [CuII(4)]2+ taking place at separate potentials (∆E ≈ 700 mV). Irreversibility and separation of the redox events are due to the self-assembling and disassembling processes following the reduction and oxidation, respectively.

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