M. Pascaly et al., Novel iron(III) complexes with imidazole containing tripodal ligands as model systems for catechol dioxygenases, INORG CHIM, 291(1-2), 1999, pp. 289-299
The iron(III) complexes [Fe(bpia)Cl-2][FeCl4], (1), [Fe(bipa)Cl-2](ClO4) (2
), and [Fe2O(bpia)(2)Cl-2]Cl-2(4MeOH (3) (bpia: bis[(2-pyridyl)methyl][(1-m
ethylimidazol-2-yl)methyl]amine, bipa: bis[(1-methylimidazol-2-yl)methyl] [
(2-pyridyl)methyl]amine) were synthesized. 1 and 2 are structural and funct
ional models for catechol 1,2-dioxygenase. All compounds are characterized
by spectroscopic methods and X-ray structure analysis. 3 was also investiga
ted by EXAFS. The coordination environment around all Fe(III) cores is dist
orted octahedral by the tripodal ligand, chloride, and in the case of 3, ad
ditionally, oxygen. Chloride and oxygen are bonded labile in the functional
ly essential cis positions to the iron core. These are the binding sites of
the catechol. The cation in 3 is formed as a dimerization product of 1 so
that the oxo ligand acts as a linear bridge with a Fe ... Fe separation of
3.5756(8) Angstrom. These properties of 3 have been used to study the ampli
tude enhancement in the EXAFS signal due to multiple scattering. In situ pr
epared iron(III) complexes with the ligands bpia and bipa show significant
intradiol catechol dioxygenase activity with respect to the cleavage of 3,5
-di-tert-butylcatechol. and pyrocatechol. (C) 1999 Elsevier Science S.A. Al
l rights reserved.