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Structural, spectroscopic, and electrochemical properties of tri- and tetradentate N-3 and N3S copper complexes with mixed benzimidazole/thioether donors

Castillo, Ivan; Ugalde-Saldivar, Victor M.; Rodriguez Solano, Laura A.; Sanchez Eguia, Brenda N.; Zeglio, Erica and Nordlander, Ebbe LU (2012) In Dalton Transactions 41(31). p.9394-9404
Abstract
Cupric and cuprous complexes of bis(2-methylbenzimidazolyl)(2-methylthiophene) amine (L-1), bis(2-methylbenzimidazolyl)benzylamine (L-2), bis(2-methylbenzimidazolyl)(2,4-dimethylphenylthioethyl)-amine (L-3), bis(1-methyl-2-methylbenzimidazolyl)benzylamine (Me2L2), and bis(1-methyl-2-methylbenzimidazolyl)(2,4-dimethylphenylthioethyl)amine (Me2L3) have been spectroscopically, structurally, and electrochemically characterised. The thioether-containing ligands L-3 and Me2L3 give rise to complexes with Cu-S bonds in solution and in the solid state, as evidenced by UV-vis spectroscopy and X-ray crystallography. The Cu2+ complexes [(LCuCl2)-Cu-1] (1), [(LCuCl2)-Cu-2] (2) and [(Me2LCuCl)-Cu-3]ClO4 (3(Me,ClO4)) are monomeric in solution according... (More)
Cupric and cuprous complexes of bis(2-methylbenzimidazolyl)(2-methylthiophene) amine (L-1), bis(2-methylbenzimidazolyl)benzylamine (L-2), bis(2-methylbenzimidazolyl)(2,4-dimethylphenylthioethyl)-amine (L-3), bis(1-methyl-2-methylbenzimidazolyl)benzylamine (Me2L2), and bis(1-methyl-2-methylbenzimidazolyl)(2,4-dimethylphenylthioethyl)amine (Me2L3) have been spectroscopically, structurally, and electrochemically characterised. The thioether-containing ligands L-3 and Me2L3 give rise to complexes with Cu-S bonds in solution and in the solid state, as evidenced by UV-vis spectroscopy and X-ray crystallography. The Cu2+ complexes [(LCuCl2)-Cu-1] (1), [(LCuCl2)-Cu-2] (2) and [(Me2LCuCl)-Cu-3]ClO4 (3(Me,ClO4)) are monomeric in solution according to ESI mass spectrometry data, as well as in the solid state. Their Cu+ analogues [(LCu)-Cu-1]ClO4, [(LCu)-Cu-2]ClO4, [(LCu)-Cu-3]ClO4 (4-6), [(BOC2LCu)-Cu-1(NCCH3)]ClO4 (4(BOC)), [(Me2LCu)-Cu-2(NCCH3)(2)]PF6 (5(Me)) and [(Me2LCu)-Cu-3](2)(ClO4)(2) (6(Me)) are also monomeric in acetonitrile solution, as confirmed crystallographically for 4(BOC) and 5(Me). In contrast, 6(Me) is dimeric in the solid state, with the thioether group of one of the ligands bound to a symmetry-related Cu+ ion. Cyclic voltammetry studies revealed that the bis(2-methylbenzimidazolyl) amine-Cu2+/Cu+ systems possess half-wave potentials in the range -0.16 to -0.08 V (referenced to the ferrocenium-ferrocene couple); these values are nearly 0.23 V less negative than those reported for related bis(picolyl) amine-derived ligands. Based on these observations, the N-3 or N3S donor set of the benzimidazole-derived ligands is analogous to previously reported chelating systems, but the electronic environment they provide is unique, and may have relevance to histidine and methionine-containing metalloenzymes. This is also reflected in the reactivity of [(Me2LCu)-Cu-2(NCCH3)(2)](+) (5(Me)) and [(Me2LCu)-Cu-3](+) (6(Me)) towards dioxygen, which results in the production of the superoxide anion in both cases. The thioether-bound Cu+ centre in 6(Me) appears to be more selective in the generation of O-2(center dot-) than 5(Me), lending evidence to the hypothesis of the modulating properties of thioether ligands in Cu-O-2 reactions. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Dalton Transactions
volume
41
issue
31
pages
9394 - 9404
publisher
Royal Society of Chemistry
external identifiers
  • wos:000306523100017
  • scopus:84864227264
ISSN
1477-9234
DOI
10.1039/c2dt30756a
language
English
LU publication?
yes
id
3c6abdf5-a0d3-47f4-9df0-4dfae5631a8f (old id 2991504)
date added to LUP
2012-08-22 14:57:23
date last changed
2017-01-01 03:36:42
@article{3c6abdf5-a0d3-47f4-9df0-4dfae5631a8f,
  abstract     = {Cupric and cuprous complexes of bis(2-methylbenzimidazolyl)(2-methylthiophene) amine (L-1), bis(2-methylbenzimidazolyl)benzylamine (L-2), bis(2-methylbenzimidazolyl)(2,4-dimethylphenylthioethyl)-amine (L-3), bis(1-methyl-2-methylbenzimidazolyl)benzylamine (Me2L2), and bis(1-methyl-2-methylbenzimidazolyl)(2,4-dimethylphenylthioethyl)amine (Me2L3) have been spectroscopically, structurally, and electrochemically characterised. The thioether-containing ligands L-3 and Me2L3 give rise to complexes with Cu-S bonds in solution and in the solid state, as evidenced by UV-vis spectroscopy and X-ray crystallography. The Cu2+ complexes [(LCuCl2)-Cu-1] (1), [(LCuCl2)-Cu-2] (2) and [(Me2LCuCl)-Cu-3]ClO4 (3(Me,ClO4)) are monomeric in solution according to ESI mass spectrometry data, as well as in the solid state. Their Cu+ analogues [(LCu)-Cu-1]ClO4, [(LCu)-Cu-2]ClO4, [(LCu)-Cu-3]ClO4 (4-6), [(BOC2LCu)-Cu-1(NCCH3)]ClO4 (4(BOC)), [(Me2LCu)-Cu-2(NCCH3)(2)]PF6 (5(Me)) and [(Me2LCu)-Cu-3](2)(ClO4)(2) (6(Me)) are also monomeric in acetonitrile solution, as confirmed crystallographically for 4(BOC) and 5(Me). In contrast, 6(Me) is dimeric in the solid state, with the thioether group of one of the ligands bound to a symmetry-related Cu+ ion. Cyclic voltammetry studies revealed that the bis(2-methylbenzimidazolyl) amine-Cu2+/Cu+ systems possess half-wave potentials in the range -0.16 to -0.08 V (referenced to the ferrocenium-ferrocene couple); these values are nearly 0.23 V less negative than those reported for related bis(picolyl) amine-derived ligands. Based on these observations, the N-3 or N3S donor set of the benzimidazole-derived ligands is analogous to previously reported chelating systems, but the electronic environment they provide is unique, and may have relevance to histidine and methionine-containing metalloenzymes. This is also reflected in the reactivity of [(Me2LCu)-Cu-2(NCCH3)(2)](+) (5(Me)) and [(Me2LCu)-Cu-3](+) (6(Me)) towards dioxygen, which results in the production of the superoxide anion in both cases. The thioether-bound Cu+ centre in 6(Me) appears to be more selective in the generation of O-2(center dot-) than 5(Me), lending evidence to the hypothesis of the modulating properties of thioether ligands in Cu-O-2 reactions.},
  author       = {Castillo, Ivan and Ugalde-Saldivar, Victor M. and Rodriguez Solano, Laura A. and Sanchez Eguia, Brenda N. and Zeglio, Erica and Nordlander, Ebbe},
  issn         = {1477-9234},
  language     = {eng},
  number       = {31},
  pages        = {9394--9404},
  publisher    = {Royal Society of Chemistry},
  series       = {Dalton Transactions},
  title        = {Structural, spectroscopic, and electrochemical properties of tri- and tetradentate N-3 and N3S copper complexes with mixed benzimidazole/thioether donors},
  url          = {http://dx.doi.org/10.1039/c2dt30756a},
  volume       = {41},
  year         = {2012},
}