A series of mononuclear iron() complexes as functional and structural model compounds for intradiol cleaving catechol dioxygenases were synthesized. For all model compounds the iron() cores are in a distorted octahedral environment derived from tripodal tetradentate N 4 -donor ligands and a catechol. Model complexes for enzymesubstrate adducts were characterized by spectroscopic and electrochemical methods, and in four cases by singlecrystal X-ray crystallography. The systematic variation of one ligand arm in the structurally characterized complexes yields a different steric shielding of the iron() center, significantly influencing the bonding of the catechol substrate and the subsequent reaction with dioxygen. The spectroscopic features and catechol cleaving activities of in situ generated complexes with the above ligands were probed. All complexes are highly reactive towards intradiol cleavage of various catechols in the presence of air. The catechol 1,2-dioxygenase reaction depends on the redox potential of both the iron() complex and the catechol derivative as well as the steric demand of the tripodal ligand. Some complexes show high catalytic activities with yields up to 84% with respect to aerial cleavage of catechols.

No abstract

No abstract

No abstract

Screening of a small library of tripod ligands resulted in the discovery of bis(2-pyridylmethyl)-(2-hydroxybenzyl)amine (HL1) as a new sensitiser, which is able to transfer its excitation energy to terbium(III). After synthesis of the acetic acid ester of HL1, a highly selective method for the determination of porcine liver esterase by means of enzyme amplified lanthanide luminescence (EALL) was developed. Enzyme-catalysed cleavage of the ester results in the formation of HL1. After excitation at 297 nm, the characteristic emission of Tb(III) at 545 nm is observed and used to determine the esterase concentration. In contrast to existing EALL methods, this method may be carried out at neutral pH and without further additives. Limit of detection for porcine liver esterase is 10(-9) mol l(-1) and limit of quantification is 3 x 10(-9) mol l(-1). A linear calibration range of two decades starting at the limit of quantification is observed.