No abstract

No abstract

Novel Fe(III)Fe(III) and Fe(II)Fe(III) complexes [Fe(2)(BBPMP)(&mgr;-OAc)(&mgr;-X)](n)() (1, X = OAc(-), n = 1+; 2, X = OH(-), n = 1+; 3, X = OAc(-), n = 0; 4, X = OH(-), n = 0), where BBPMP(3)(-) is the anion of 2,6-bis[(2-hydroxybenzyl)(2-pyridylmethyl)aminomethyl]-4-methylphenol, and OAc(-) is acetate, were prepared in order to provide models for the active site of purple acid phosphatases (PAPs). Complex 1 was obtained by the reaction of H(3)BBPMP with Fe(ClO(4))(2).6H(2)O in methanol and sodium acetate trihydrate under ambient conditions, while complex 3 was synthesized as described for 1, under an argon atmosphere with low levels of dioxygen. 2 was isolated from 1in acetonitrile by a substitution of the bridging acetate group by hydroxide, while 4 was generated in solution during a spectropotentiostatic experiment on 2, under argon. Complex 1, [Fe(III)(2)(BBPMP)(&mgr;-OAc)(2)]ClO(4).H(2)O, has been characterized by X-ray crystallography. Crystal data: monoclinic, space group P2(1)/n, a = 14.863(5) Å, b = 12.315(3) Å, c = 20.872(8) Å, beta = 90.83(3) degrees, Z = 4. IR, Mössbauer, magnetic, electronic absorption, and electrochemical properties of 1-3 have been investigated, and some of these properties represent a contribution to the understanding of the dinuclear iron center of PAPs. Complexes 2, [Fe(III)(2)(BBPMP)(&mgr;-OAc)(&mgr;-OH)]ClO(4) (lambda(max) = 568 nm/epsilon = 4760 M(-)(1) cm(-)(1)), and 4 [Fe(II)Fe(III)(BBPMP)(&mgr;-OAc)(&mgr;-OH)] (lambda(max) = 516 nm/epsilon = 4560 M(-)(1) cm(-)(1)), constitute good synthetic analogues for the chromophoric site for the oxidized and reduced forms, respectively, of the enzyme.

No abstract

Three new iron(III) complexes with the ligand N,N'-bis(2-hydroxybenzyl)-N,N'-bis(pyridin-2-ylmethyl)ethylenediamine, H2bbpen, containing electron-donating and -withdrawing groups (Me, Br, NO2) in the 5-position of the phenol rings were synthesized and fully characterized by IR spectroscopy, ESI mass spectrometry, and CHN elemental analyses. X-ray structures of the iron(III) complexes containing NO2 and Me groups were determined. The effects of the substituents on the electronic properties of the complexes were detected by UV-visible spectroscopy, cyclic voltammetry, and X-ray crystallography. Linear correlations between the Hammett parameter for the substituents (sigma(p)) and the Fe(III)/Fe(II) redox potentials or ligand-metal charge-transfer (LMCT) processes of the complexes were obtained. A theoretical study using DFT is presented and shows good agreement between the experimental and calculated data.