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Issue 40, 2011
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Cobalt(ii), nickel(ii) and copper(ii) complexes of a hexadentate pyridine amide ligand. Effect of donor atom (ethervs. thioether) on coordination geometry, spin-state of cobalt and MIII–MII redox potential

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Abstract

Using an acyclic hexadentate pyridine amide ligand, containing a –OCH2CH2O– spacer between two pyridine-2-carboxamide units (1,4-bis[o-(pyrydine-2-carboxamidophenyl)]-1,4-dioxabutane (H2L9), in its deprotonated form), four new complexes, [CoII(L9)] (1) and its one-electron oxidized counterpart [CoIII(L9)][NO3]·2H2O (2), [NiII(L9)] (3) and [CuII(L9)] (4), have been synthesized. Structural analyses revealed that the CoII centre in 1 and the NiII centre in 3 are six-coordinate, utilizing all the available donor sites and the CuII centre in 4 is effectively five-coordinated (one of the ether O atoms does not participate in coordination). The structural parameters associated with the change in the metal coordination environment have been compared with corresponding complexes of thioether-containing hexadentate ligands. The μeff values at 298 K of 1–4 correspond to S = 3/2, S = 0, S = 1 and S = 1/2, respectively. Absorption spectra for all the complexes have been investigated. EPR spectral properties of the copper(II) complex 4 have been investigated, simulated and analyzed. Cyclic voltammetric experiments in CH2Cl2 reveal quasireversible CoIII–CoII, NiIII–NiII and CuII–CuI redox processes. In going from ether O to thioether S coordination, the effect of the metal coordination environment on the redox potential values of CoIII–CoII (here the effect of spin-state as well), NiIII–NiII and CuII–CuI processes have been systematically analyzed.

Graphical abstract: Cobalt(ii), nickel(ii) and copper(ii) complexes of a hexadentate pyridine amide ligand. Effect of donor atom (ethervs. thioether) on coordination geometry, spin-state of cobalt and MIII–MII redox potential

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Supplementary files

Article information


Submitted
14 Apr 2011
Accepted
09 Sep 2011
First published
27 Sep 2011

Dalton Trans., 2011,40, 10758-10768
Article type
Paper

Cobalt(II), nickel(II) and copper(II) complexes of a hexadentate pyridine amide ligand. Effect of donor atom (ethervs. thioether) on coordination geometry, spin-state of cobalt and MIII–MII redox potential

S. Pandey, P. P. Das, A. K. Singh and R. Mukherjee, Dalton Trans., 2011, 40, 10758
DOI: 10.1039/C1DT10661A

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