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. Issue 13 (26th March 2014)

• Record Type: Journal Article
• Authors: Das, Biswanath; Daver, Henrik; Singh, Amrendra; Singh, Reena; Haukka, Matti; Demeshko, Serhiy; Meyer, Franc; Lisensky, George; Jarenmark, Martin; Himo, Fahmi; Nordlander, Ebbe
• Is Part Of: European journal of inorganic chemistry. Issue 13(2014)
• Page Start: 2204
• Page End: 2212
• Publication Date: 2014-03-26
• Subjects: Metalloenzymes -- Mixed‐valent compounds -- Moessbauer spectroscopy -- Density functional calculations -- Transition states -- Hydrolysis; Chemistry, Inorganic -- Periodicals; Organometallic chemistry -- Periodicals; Bioinorganic chemistry -- Periodicals; Solid state chemistry -- Periodicals; 546
• DOI: 10.1002/ejic.201301375
• Languages: English
• ISSNs: 1434-1948

Abstract

Abstract: The heterodinuclear mixed‐valence complex [FeMn(ICIMP)(OAc)2 Cl] (1 ) {H2 ICIMP = 2‐( N ‐carboxylmethyl)‐[ N ‐( N ‐methylimidazolyl‐2‐methyl)aminomethyl]‐[6‐( N ‐isopropylmethyl)‐[ N ‐( N ‐methylimidazolyl‐2‐methyl)]aminomethyl‐4‐methylphenol], an unsymmetrical N4 O2 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 in1 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. Mössbauer spectroscopy shows that the iron ion in1 is high‐spin Fe III . Two quasi‐reversible redox reactions for the complex, attributed to the Fe III Mn II /Fe II Mn II (at –0.67 V versus Fc/Fc + ) and Fe III Mn II /Fe III Mn III (at 0.84 V), were observed by means of cyclic voltammetry. Complex1, with an Fe III –Mn II 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 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. Abstract : Catalytic hydrolysis of a phosphodiester bond was investigated by using a mixed‐valence heterodinuclear Fe III Mn II complex of the dinucleating ligand as catalyst. Computational modeling and kinetic results indicate that a μ‐hydroxo Fe III Mn II complex is the active catalyst that binds the substrate in a monodentate fashion at the Mn ion.