Synthesis and characterization of Fe^III(μ-OH)Zn^II complexes: Effects of a second coordination sphere and increase in the chelate ring size on the hydrolysis of a phosphate diester and DNA

The synthesis and characterization of three ligands and their respective heterobinuclear Fe^IIIZn^II complexes were carried out, with the goal of mimicking the active site of purple acid phosphatases (PAPs). The ligand 2-hydroxy-3-(((2-hydroxy-5-methyl-3-(((2-(pyridin-2-yl)ethyl)(pyridin-2-ylmethyl)amino)methyl)benzyl)(pyridin-2ylmethyl)amino)methyl)-5-methylbenzaldehyde (H₂L²) was synthesized and its complex (Fe^IIIZn^IIL²) was used as a basis for comparison with similar complexes previously published in the literature. Subsequent modifications were conducted in the aldehyde group, where 1,2-ethanediamine and 1,4-diaminobutane were used as side chain derivatives. The compounds Fe^IIIZn^IIL² (1), Fe^IIIZn^IIL²-et (2) and Fe^IIIZn^IIL²-but (3) were characterized by spectroscopic methods (infrared and UV-Vis) and ESI-MS spectrometry. Theoretical calculations were performed to provide insights into the complex structures with Fe^IIIZn^II structures. The hydrolytic activity was analyzed both with the model substrate 2,4-BDNPP and with DNA catalyzed by complexes 1, 2 and 3.