scholarly journals Synthesis and Characterisation of New Symmetrical Binucleating Ligands and Their Binuclear Copper(II) Complexes

2014 ◽  
Vol 2014 ◽  
pp. 1-9
Author(s):  
K. Jothivenkatachalam ◽  
S. Chandra Mohan
Keyword(s):  
Electron Transfer ◽  
Exchange Interaction ◽  
Variable Temperature ◽  
Esr Spectra ◽  
Single Step ◽  
Binuclear Copper ◽  
Magnetic Studies ◽  
Weak Exchange ◽  
Broad Signal ◽  
Binucleating Ligands

New symmetrical binucleating ligands N,N-bis[2-hydroxy-5-methyl-3-(4-methyl-piperazinomethyl)benzyl]-alkylamines L1 and L2 and their copper(II) complexes [Cu2L(X)2]·2H2O, where X = CH3COO−, C6H5COO−, Cl−, and ClO4-, were prepared and characterised. All the complexes undergo quasi-reversible reduction at negative potential (E = −0.48 to −1.02 V). The acetate and benzoate complexes undergo a two-step single electron transfer at –0.48 to –0.60 V and −0.9 to −1.02 V. The chloro and perchlorate complexes undergo a single step two-electron transfer at −0.55 to −0.75 V. Variable temperature magnetic studies show the presence of weak exchange interaction for acetate (−2 J around 25 to 40 cm−1) and benzoate (−2 J around 45 to 55 cm−1) bridged complexes and no exchange interaction is found for chloro and perchlorate complexes. ESR spectra of chloro and perchlorate complexes are like mononuclear copper(II) complexes with hyperfine splitting (A = 165 ± 5, g∥ = 2.17–2.23, and g⊥ = 2.05–2.10). The ESR spectra of acetate and benzoate complexes are like binuclear copper(II) complexes with broad signal (g = 2.2).

Synthesis, structural and magnetic properties of macrocyclic aza-amido binuclear copper(II) complexes

1989 ◽  
Vol 67 (4) ◽  
pp. 662-670 ◽  
Author(s):  
Sanat K. Mandal ◽  
Laurence K. Thompson ◽  
Michael J. Newlands ◽  
Amal K. Biswas ◽  
Bibhutosh Adhikary ◽  
...  
Keyword(s):  
Variable Temperature ◽  
Complex Iii ◽  
Azomethine Nitrogen ◽  
X Ray Diffraction ◽  
Binuclear Copper ◽  
Magnetic Studies ◽  
Monoclinic System ◽  
Space Group ◽  
Pyramidal Geometry ◽  
Square Planar

Binuclear, antiferromagnetically coupled, macrocyclic copper(II) complexes, [Cu2(C28H32N4O4)]•H2O (II) and [Cu2(C36H32N4O4)]•CH3CN•H2O (III), involving asymmetric ligands with two deprotonated amide, two azomethine nitrogen, and two phenoxide donors at the binuclear centre, have been synthesized and characterized by single-crystal X-ray diffraction and variable temperature magnetic studies. Complex II crystallizes in the monoclinic system, space group P21/n, with a = 16.4854(9) Å, b = 7.6005(13) Å, c = 21.1617(11) Å, β = 104.090(5)°, Z = 4, Rf = 0.068 for 2062 significant reflections. The two copper(II) centres have square planar N2O2 donor sets with two phenoxide oxygen atoms bridging the copper centres with a copper–copper separation of 2.898(2) Å. A long copper–oxygen (amide) contact (2.808(10) Å) forms a weak dimer association. Complex III crystallizes in the triclinic system, space group [Formula: see text], with a = 8.7771(9) Å, b = 12.3983(16) Å, c = 15.7299(16) Å, α = 85.003(11)°, β = 84.574(8)°, γ = 76.838(10)°, Z = 2, Rf = 0.041 for 2966 significant reflections. The two copper(II) centres have distorted square-pyramidal geometry involving an N2O2 in plane donor set and two phenoxide oxygen bridges with a copper–copper separation of 3.018(1) Å. The fifth coordination site at each copper centre involves an amide oxygen from a neighbouring molecule (Cu(1)—O 2.371(4), Cu(2)—O 2.413(3) Å) in a staggered intermolecular array. Very strong antiferromagnetic exchange is observed in both cases (−2J = 689 ± 7 cm−1 (II), −2J = 816 ± 8 cm−1 (III)). Keywords: macrocycles, binuclear copper(II) complexes.

Synthesis and Reactivity of Copper(II) Complexes with New Binucleating Ligands Derived from 16-or 20-Membered N4-Macrocycles

1990 ◽  
Vol 45 (1) ◽  
pp. 39-44 ◽  
Author(s):  
Yuzo Nishida
Keyword(s):  
Catalytic Activity ◽  
Metal Ions ◽  
Binuclear Complex ◽  
Esr Spectra ◽  
Cyclic Voltammograms ◽  
Binuclear Complexes ◽  
Binuclear Copper ◽  
Coordination Sites ◽  
Trinuclear Complexes ◽  
Binucleating Ligands

Abstract New binucleating ligands, (L1) N ,N′,N″,N‴-tetrakis(2-benzimidazolylmethyl)-1,4,9,12-tetra-azacyclohexadecane, and (L2) N ,N′,N″,N‴-tetrakis(2-benzimidazolylmethyl)-1,4,11,14-tetra-azacycloeicosane were prepared. From the reaction mixture of copper(II) salt and the ligand, new binuclear copper(II) complexes, Cu2(L1) (NO3)4 (1), Cu2(L2)(NO3)4 (2), Cu2(L2)Br4 (3), and trinuclear complexes, Cu3(L1)Cl6 (4), and Cu3(L2)Cl6 (5) were obtained. Cyclic voltammograms revealed that the trinuclear complexes 4 and 5 are composed with the binuclear complex (1 or 2) and [CuCl4]2-. The interaction between two metal ions in the binuclear complexes are confirmed on the basis of the ESR spectra. These binuclear complexes exhibit higher catalytic activity for the oxidation of TMPD by O2 molecule than those of structurally rigid binuclear copper(II) complexes and of flexible binuclear complexes in which two copper(II) coordination sites are linked by a single polyatomic chain.

ESR spectra of biradicals with weak exchange interaction

1966 ◽  
Vol 1 (2) ◽  
pp. 163-166 ◽  
Author(s):  
A. L. Buchachenko ◽  
V. A. Golubev ◽  
A. A. Medzhidov ◽  
E. G. Rozantsev
Keyword(s):  
Exchange Interaction ◽  
Esr Spectra ◽  
Weak Exchange ◽  
Weak Exchange Interaction

Electrochemical behaviour and ESR spectra of nitro substituted mono- and dibenzoylmethylenebenzthiazolines and selenazolines

1979 ◽  
Vol 44 (5) ◽  
pp. 1540-1551 ◽  
Author(s):  
Jaro Komenda ◽  
Jiří Huzlík
Keyword(s):  
Electron Transfer ◽  
Esr Spectroscopy ◽  
Electrochemical Behaviour ◽  
Spectroscopic Studies ◽  
Esr Spectra ◽  
Slow Electron

Compounds of the type of 2-(4'-nitrobenzoyl)methylene-3-ethylbenzothiazoline (I) and 2-bis-(p-nitrobenzoyl)methylene-3-ethylbenzothiazoline (II) were studied polarographically and by ESR spectroscopy to obtain informations about their electrochemical and follow-up reactions and their conformation. Whereas with compounds of the type I the conjugation in their molecules is preserved, with type II the coplanarity of the molecules is disturbed, which is manifested in the values of the splitting constants of the ESR spectra and a slow electron transfer between both nitrophenyl substituents. These conclusions are supported by NMR spectroscopic studies.

Bromine oxidation of a nickel(II) bis(oxime-imine) complex. Evidence for a single-step outer-sphere two-electron transfer?

1987 ◽  
Vol 26 (19) ◽  
pp. 3089-3094 ◽  
Author(s):  
A. Graham Lappin ◽  
Peter Osvath ◽  
Subhash Baral
Keyword(s):  
Electron Transfer ◽  
Outer Sphere ◽  
Single Step

Interaction between Binuclear Copper(I) Complexes and the Dioxygen Molecule Investigated by Electrochemical Methods

1992 ◽  
Vol 47 (1) ◽  
pp. 109-114 ◽  
Author(s):  
Yuzo Nishida ◽  
Izumi Watanabe ◽  
Kei Unoura
Keyword(s):  
Cyclic Voltammetry ◽  
Thin Layer ◽  
Electrochemical Reduction ◽  
High Reactivity ◽  
Electrochemical Methods ◽  
Tridentate Ligand ◽  
Cyclic Voltammograms ◽  
Binuclear Copper ◽  
Alkyl Chains ◽  
Binucleating Ligands

The cyclic voltammograms of some binuclear copper(II) compounds with binucleating ligands where two molecules of tridentate ligand, N, N -bis(benzimidazol-2-ylmethyl)amine are linked by several alkyl chains, were measured under both argon and dioxygen. The results demonstrate that the binuclear copper(I) species produced by electrochemical reduction exhibit high reactivity towards dioxygen, while the reaction of the corresponding mononuclear species with oxygen is very slow. Thin-layer coulometry ([binuclear copper(I)]/[O2] = 0.47 - 10.6) and thin-layer cyclic voltammetry ([binuclear copper(I)]/[O2] = 4.3 - 10.6 ) revealed that two molecules of the binuclear copper(I) species react with one molecule of dioxygen.

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