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A Heterobimetallic FeIIIMnII Complex of an Unsymmetrical Dinucleating Ligand: A Structural and Functional Model Complex for the Active Site of Purple Acid Phosphatase of Sweet Potato

Das, Biswanath LU ; Daver, Henrik; Singh, Amrendra LU ; Singh, Reena LU ; Haukka, Matti; Demeshko, Serhiy; Meyer, Franc; Lisensky, George; Jarenmark, Martin LU and Himo, Fahmi, et al. (2014) In European Journal of Inorganic Chemistry 2014(13). p.2204-2212
Abstract
The heterodinuclear mixed-valence complex [FeMn(ICIMP)(OAc)(2)Cl] (1) {H2ICIMP = 2-(N-carboxylmethyl)-[N-(N-methylimidazolyl-2-methyl)aminomethyl]-[6-(N-isopropylmethyl)-[N-(N-methylimidazolyl-2-methyl)]aminomethyl-4-methylphenol], an unsymmetrical N4O2 donor ligand} has been synthesized and fully characterized by several spectroscopic techniques as well as by X-ray crystallography. The crystal structure of the complex reveals that both metal centers in 1 are six-coordinate with the chloride ion occupying the sixth coordination site of the Mn-II ion. The phenoxide moiety of the ICIMP ligand and both acetate ligands bridge the two metal ions of the complex. Mossbauer spectroscopy shows that the iron ion in 1 is high-spin Fe-III. Two... (More)
The heterodinuclear mixed-valence complex [FeMn(ICIMP)(OAc)(2)Cl] (1) {H2ICIMP = 2-(N-carboxylmethyl)-[N-(N-methylimidazolyl-2-methyl)aminomethyl]-[6-(N-isopropylmethyl)-[N-(N-methylimidazolyl-2-methyl)]aminomethyl-4-methylphenol], an unsymmetrical N4O2 donor ligand} has been synthesized and fully characterized by several spectroscopic techniques as well as by X-ray crystallography. The crystal structure of the complex reveals that both metal centers in 1 are six-coordinate with the chloride ion occupying the sixth coordination site of the Mn-II ion. The phenoxide moiety of the ICIMP ligand and both acetate ligands bridge the two metal ions of the complex. Mossbauer spectroscopy shows that the iron ion in 1 is high-spin Fe-III. Two quasi-reversible redox reactions for the complex, attributed to the (FeMnII)-Mn-III/(FeMnII)-Mn-II (at -0.67 V versus Fc/Fc(+)) and (FeMnII)-Mn-III/(FeMnIII)-Mn-III (at 0.84 V), were observed by means of cyclic voltammetry. Complex 1, with an Fe-III-Mn-II distance of 3.58 angstrom, may serve as a model for the mixed-valence oxidation state of purple acid phosphatase from sweet potato. The capability of the complex to effect organophosphate hydrolysis (phosphatase activity) has been investigated at different pH levels (5.5-11) by using bis(2,4-dinitrophenyl)phosphate (BDNPP) as the substrate. Density functional theory calculations indicate that the substrate coordinates to the Mn-II ion. In the transition state, a hydroxide ion that bridges the two metal ions becomes terminally coordinated to the Fe-III ion and acts as a nucleophile, attacking the phosphorus center of BDNPP with the concomitant dissociation of the leaving group. (Less)
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subject
keywords
Metalloenzymes, Mixed-valent compounds, Moessbauer spectroscopy, Density, functional calculations, Transition states, Hydrolysis
in
European Journal of Inorganic Chemistry
volume
2014
issue
13
pages
2204 - 2212
publisher
John Wiley & Sons
external identifiers
  • wos:000335197600004
  • scopus:84899838503
ISSN
1099-0682
DOI
10.1002/ejic.201301375
language
English
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yes
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4d4af021-2024-4738-bf65-a63bbb457820 (old id 4470079)
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2014-06-19 10:50:56
date last changed
2017-10-22 03:28:39
@article{4d4af021-2024-4738-bf65-a63bbb457820,
  abstract     = {The heterodinuclear mixed-valence complex [FeMn(ICIMP)(OAc)(2)Cl] (1) {H2ICIMP = 2-(N-carboxylmethyl)-[N-(N-methylimidazolyl-2-methyl)aminomethyl]-[6-(N-isopropylmethyl)-[N-(N-methylimidazolyl-2-methyl)]aminomethyl-4-methylphenol], an unsymmetrical N4O2 donor ligand} has been synthesized and fully characterized by several spectroscopic techniques as well as by X-ray crystallography. The crystal structure of the complex reveals that both metal centers in 1 are six-coordinate with the chloride ion occupying the sixth coordination site of the Mn-II ion. The phenoxide moiety of the ICIMP ligand and both acetate ligands bridge the two metal ions of the complex. Mossbauer spectroscopy shows that the iron ion in 1 is high-spin Fe-III. Two quasi-reversible redox reactions for the complex, attributed to the (FeMnII)-Mn-III/(FeMnII)-Mn-II (at -0.67 V versus Fc/Fc(+)) and (FeMnII)-Mn-III/(FeMnIII)-Mn-III (at 0.84 V), were observed by means of cyclic voltammetry. Complex 1, with an Fe-III-Mn-II distance of 3.58 angstrom, may serve as a model for the mixed-valence oxidation state of purple acid phosphatase from sweet potato. The capability of the complex to effect organophosphate hydrolysis (phosphatase activity) has been investigated at different pH levels (5.5-11) by using bis(2,4-dinitrophenyl)phosphate (BDNPP) as the substrate. Density functional theory calculations indicate that the substrate coordinates to the Mn-II ion. In the transition state, a hydroxide ion that bridges the two metal ions becomes terminally coordinated to the Fe-III ion and acts as a nucleophile, attacking the phosphorus center of BDNPP with the concomitant dissociation of the leaving group.},
  author       = {Das, Biswanath and Daver, Henrik and Singh, Amrendra and Singh, Reena and Haukka, Matti and Demeshko, Serhiy and Meyer, Franc and Lisensky, George and Jarenmark, Martin and Himo, Fahmi and Nordlander, Ebbe},
  issn         = {1099-0682},
  keyword      = {Metalloenzymes,Mixed-valent compounds,Moessbauer spectroscopy,Density,functional calculations,Transition states,Hydrolysis},
  language     = {eng},
  number       = {13},
  pages        = {2204--2212},
  publisher    = {John Wiley & Sons},
  series       = {European Journal of Inorganic Chemistry},
  title        = {A Heterobimetallic FeIIIMnII Complex of an Unsymmetrical Dinucleating Ligand: A Structural and Functional Model Complex for the Active Site of Purple Acid Phosphatase of Sweet Potato},
  url          = {http://dx.doi.org/10.1002/ejic.201301375},
  volume       = {2014},
  year         = {2014},
}