M. Palaniandavar et R. Viswanathan, IRON(III) COMPLEXES OF PHENOLATE LIGANDS AS MODELS FOR CATECHOL DIOXYGENASES, Proceedings of the Indian Academy of Sciences. Chemical sciences, 108(3), 1996, pp. 235-249
Catechol 1,2-dioxygenase (CTD) and protocatechuate 3,4-dioxygenase (PC
D) enzymes catalyse the oxidative cleavage of catechols to cis, cis-mu
conic acids with the incorporation of molecular oxygen. In our laborat
ory two series of iron(III) complexes of linear tridentate and tripoda
l tetradentate phenolate ligands have been characterised using IR, UV-
Vis and EPR spectral and electrochemical techniques. The X-ray crystal
structure of a few of the complexes have been determined. The interac
tions of the complexes with a variety of monodentate and bidentate het
erocyclic bases as well as phenols have been investigated. The interac
tions with catecholate anions reveal changes in the phenolate-to-iron(
III) charge transfer band, which are remarkably similar to catechol di
oxygenase-substrate complexes. The redox behaviour of the complexes an
d their 1:1 adducts with 3,5-di-t-butyl-catechol (H2DBC) has been inve
stigated. All the complexes catalyse the oxidative cleavage of H(2)DEC
by molecular oxygen to yield cis,cis-muconic anhydride. The structure
, redox and catalytic activities of the iron(III) complexes have been
discussed vis-a-vis those of the enzymes.