A new heterobinuclear (FeCuII)-Cu-III complex with a single terminal Fe-III-O(phenolate) bond. Relevance to purple acid phosphatases and nucleases

摘要

A novel heterobinuclear mixed valence complex [Fe-III Cu-II(BPBPMP)(OAc)(2)] ClO4, 1, with the unsymmetrical N5O2 donor ligand 2-bis[{(2-pyridylmethyl) aminomethyl}-6-{(2-hydroxybenzyl)(2-pyridylmethyl)} aminomethyl]-4-methylphenol (H2BPBPMP) has been synthesized and characterized. A combination of data from mass spectrometry, potentiometric titrations, X-ray absorption and electron paramagnetic resonance spectroscopy, as well as kinetics measurements indicates that in ethanol/water solutions an [Fe-III -(mu) OH - Cu-II OH2](+) species is generated which is the likely catalyst for 2,4-bis( dinitrophenyl) phosphate and DNA hydrolysis. Insofar as the data are consistent with the presence of an Fe-III-bound hydroxide acting as a nucleophile during catalysis, 1 presents a suitable mimic for the hydrolytic enzyme purple acid phosphatase. Notably, 1 is significantly more reactive than its isostructural homologues with different metal composition (Fe-III M-II, where M-II is Zn-II, Mn-II, Ni-II, or Fe-II). Of particular interest is the observation that cleavage of double-stranded plasmid DNA occurs even at very low concentrations of 1 (2.5 mu M), under physiological conditions ( optimum pH of 7.0), with a rate enhancement of 2.7 x 10(7) over the uncatalyzed reaction. Thus, 1 is one of the most effective model complexes to date, mimicking the function of nucleases.