TY - JOUR

T1 - A heterobimetallic FeIIIMnII complex of an unsymmetrical dinucleating ligand

T2 - A structural and functional model complex for the active site of purple acid phosphatase of sweet potato

AU - Das, Biswanath

AU - Daver, Henrik

AU - Singh, Amrendra

AU - Singh, Reena

AU - Haukka, Matti

AU - Demeshko, Serhiy

AU - Meyer, Franc

AU - Lisensky, George

AU - Jarenmark, Martin

AU - Himo, Fahmi

AU - Nordlander, Ebbe

PY - 2014/5

Y1 - 2014/5

N2 - The heterodinuclear mixed-valence complex [FeMn(ICIMP)(OAc)2Cl] (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 MnII ion. The phenoxide moiety of the ICIMP ligand and both acetate ligands bridge the two metal ions of the complex. Mössbauer spectroscopy shows that the iron ion in 1 is high-spin FeIII. Two quasi-reversible redox reactions for the complex, attributed to the FeIIIMnII/Fe IIMnII (at -0.67 V versus Fc/Fc+) and Fe IIIMnII/FeIIIMnIII (at 0.84 V), were observed by means of cyclic voltammetry. Complex 1, with an Fe III-MnII distance of 3.58 Å, 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 MnII ion. In the transition state, a hydroxide ion that bridges the two metal ions becomes terminally coordinated to the FeIII ion and acts as a nucleophile, attacking the phosphorus center of BDNPP with the concomitant dissociation of the leaving group.

AB - The heterodinuclear mixed-valence complex [FeMn(ICIMP)(OAc)2Cl] (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 MnII ion. The phenoxide moiety of the ICIMP ligand and both acetate ligands bridge the two metal ions of the complex. Mössbauer spectroscopy shows that the iron ion in 1 is high-spin FeIII. Two quasi-reversible redox reactions for the complex, attributed to the FeIIIMnII/Fe IIMnII (at -0.67 V versus Fc/Fc+) and Fe IIIMnII/FeIIIMnIII (at 0.84 V), were observed by means of cyclic voltammetry. Complex 1, with an Fe III-MnII distance of 3.58 Å, 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 MnII ion. In the transition state, a hydroxide ion that bridges the two metal ions becomes terminally coordinated to the FeIII ion and acts as a nucleophile, attacking the phosphorus center of BDNPP with the concomitant dissociation of the leaving group.

KW - Density functional calculations

KW - Hydrolysis

KW - Metalloenzymes

KW - Mixed-valent compounds

KW - Moessbauer spectroscopy

KW - Transition states

UR - http://www.scopus.com/inward/record.url?scp=84899838503&partnerID=8YFLogxK

U2 - 10.1002/ejic.201301375

DO - 10.1002/ejic.201301375

M3 - Journal article

AN - SCOPUS:84899838503

SP - 2204

EP - 2212

JO - European Journal of Inorganic Chemistry

JF - European Journal of Inorganic Chemistry

SN - 1434-1948

IS - 13

ER -