| Abstract
| - New μ-oxo-diferric complexes have been designed for hydrolysis of phosphodiesters. To mimic the diiron activesite of purple acid phosphatase, a combinatorial method has been used to select complexes containing two distinctiron coordination spheres. The introduction of a bidentate ligand, a substituted phenanthroline (L) into complex 1,[Fe2O(bipy)4(OH2)2](NO3)4, generates in solution the complex [Fe2O(bipy)3(L)(OH2)2](NO3)4 as shown by ESI/MSand 1H NMR studies. The latter complex was found to be 20-fold more active than complex 1. On the basis ofkinetic studies, we demonstrated that the complex [Fe2O(bipy)3(L)(OH)(OH2)](NO3)3 was the active species and thereaction proceeded through the formation of a ternary complex in which one iron binds a hydroxide and the second,the substrate. At nonsaturating concentrations of the substrate, the increased activity with increased methyl substituentsin L was due to an increased affinity of the complex for the substrate. The activity of [Fe2O(bipy)3(33‘44‘Me2Phen)(OH2)2](NO3)4 [33‘44‘Me2Phen = 3,3‘,4,4‘-dimethyl-1,10-phenanthroline] was found to be comparable to thatreported for Co(III) or Ce(IV) complexes.
- The substitution of a bipyridine ligand (bipy) with a methylated phenanthroline in the [Fe2O(bipy)2(OH2)2](NO3)4 complex generated a new dinuclear complex with greatly improved activities during phosphodiester hydrolysis.
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