A New Model for the Reduced Form of Purple Acid Phosphatase: Structure and Properties of [Fe2BPLMP(OAc)2](BPh4)2

Seon Hwa Yim, Ho Jin Lee, Kang Bong Lee, Seong Ju Kang, Nam Hwi Hur, Ho G. Jang

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Abstract

[FeIIFeIIIBPLMP(OAc)2](BPh 4)2 (1), a new model for the reduced form of the purple acid phosphatases. has been synthesized by using a dinucleating ligand, 2,6-bis[((2-pyridylmethyl)(6-methyl-2-pyridylmethyl)amino) methyl]-4-methylphenol (HBPLMP). Complex 1 has been characterized by X-ray diffraction method as having (μ-phenoxo)bis(acetato)diiron core. Complex 1 was crystallized in the monoclinic space group C2/c with the following cell parameters: a=41.620(6) Å, b=14.020(3) Å, c=27.007(4) Å, β=90.60(2)°, and Z=8. The iron centers in the complex 1 are ordered as indicated by the difference in the Fe-O bond lengths which match well with typical FeIII-O and FeII-O bond lengths. Complex 1 has been studied by electronic spectral, NMR, EPR, SQUID, and electochemical methods. Complex 1 exhibits strong bands at 592 nm, 1380 nm in CH3CN (ε= 1.0× 103, 3.0× 102). These are assigned to phenolate-to-FeIII and intervalence charge-transfer transitions, respectively. Its NMR spectrum exhibits sharp isotropically shifted resonances, which number half of those expected for a valence-trapped species, indicating that electron transfer between FeII and FeIII centers is faster than NMR time scale. This complex undergoes quasireversible one-electron redox processes. The FeIII2/FeIIFeIII and FeIIFeIII/ FeII2 redox couples are at 0.655 and -0.085 V vs SCE, respectively. It has Kcomp=3.3 × 1012 representing that BPLMP/bis(acetate) ligand combination stabilizes a mixed-valence FeIIFeIII complex in the air. Complex 1 exhibits a broad EPR signal centered near g=1.55 which is a characteristic feature of the antiferromagnetically coupled high-spin FeIIFeIII system (Stotal=l/2). This is consistent with the magnetic susceptibility study showing the weak antiferromagnetic coupling (J=- 4.6 cm-1, H=-2JS1·S2) between FeII and FeIII center.

Original languageEnglish
Pages (from-to)654-660
Number of pages7
JournalBulletin of the Korean Chemical Society
Volume19
Issue number6
Publication statusPublished - 1998 Dec 1

ASJC Scopus subject areas

  • Chemistry(all)

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