Towards a model for the oxidized form of purple acid phosphatase: crystal structure and magnetic properties of a binuclear iron(III) complex containing phosphate ligands

Abstract

A novel binuclear iron() complex [{FeL[O 2 P(OPh) 2 ]} 2 ][ClO 4 ] 2 was synthesized and characterized by X-ray singlecrystal structure analysis, where HL is bis(benzimidazol-2-ylmethyl)(2-hydroxyethyl)amine. The crystals are triclinic, space group P1 ¯, with a = 11.523(9), b = 11.809(6), c = 13.406(4) Å, α = 68.52(4), β = 71.41(5), γ = 71.85(6)Њ and Z = 1. The structure shows that the iron() ions are bridged by the oxygen atoms of two L ligands and a phosphate ligand is terminally co-ordinated to each iron(). Magnetic susceptibility measurements in the range 4.2-300 K and subsequent calculations based on an isotropic Heisenberg model suggest antiferromagnetic coupling between the iron() ions with J = Ϫ17.5 cm Ϫ1 .

A new FeIII(µ-OCH3)2(µ-OAc)FeIII complex containing phenolate and imidazole ligands as a structural model for the active site of non-heme diiron enzymes†

“…The ligand reacts in methanol with Fe(ClO 4 ) 3 ؒnH 2 O and NaOAcؒ3H 2 O, in a 1 : 1 : 3 stoichiometry, producing complex 1. The IR spectrum of 1 is similar to that of the free ligand HBHA and it differs only in: a) the appearance of two bands at 1544 and 1452 cm Ϫ1 , with ∆ ≈ 92 cm Ϫ1 , attributed to the ν asym and ν sym stretching modes of the acetate anion coordinated to the Fe III centres in the bridging form, 27 b) the bands at 1112 and 1034 cm Ϫ1 attributed to the perchlorate counter-ion, 27 c) the bands at 756 and 534 cm Ϫ1 that could be attributed to the ν asym and ν sym Fe-O-Fe stretching, 28 respectively, and d) the absence of the band at 1354 cm Ϫ1 attributed to the δ(O-H) mode, indicating that the phenol groups are coordinated in the deprotonated form.…”

The first iron(III)–nickel(II) heterodinuclear complex containing both terminal and bridged phosphato ligands relevant to structural core models for dimetalloenzymes

“…8- 11 The diiron complexes with terminally coordinated phosphate ligands, however, are poorly understood. 12, 13 Very recently we reported a rare diiron complex [Fe 2 (HPTB)-{µ-O 2 P(OPh) 2 }{O 2 P(OPh) 2 } 2 ](ClO 4 ) 2 (1), where HPTB is the anion of N,N,NЈ,NЈ-tetrakis(2-benzimidazolylmethyl)-2hydroxy-1,3-diaminopropane (Fig. 1).…”

Three new supramolecular networks formed via hydrogen bonding interactions: Syntheses, crystal structures and magnetic properties

“…The above range of negative J value is observed for other dialkoxo-or dihydroxo-bridged diiron(III) complexes [21]. J values of some diiron complexes using the formalism are listed in Table 3.…”