A Synthetic Pathway for an Unsymmetrical N5O2 Heptadentate Ligand and Its Heterodinuclear Iron(III)Zinc(II) Complex: A Biomimetic Model for the Purple Acid Phosphatases

One major field of interest in bioinorganic chemistry is the design and synthesis of inorganic compounds with low molecular mass, showing structural, spectroscopic, and reactivity properties that mimic enzymes, such as purple acid phosphatases (PAPs). In this study, the unsymmetrical heptadentate ligand 2-[(4,7-diisopropyl-1,4,7-triazacyclonon-1-yl)methyl]-6-{[(2-hydroxybenzyl)(pyridin-2-ylmethyl)-amino]methyl}-4-methylphenol (H2L) and its first mixed-valence complex [FeIIIZnII(L)(mu-OAc)2]ClO4 (1) were synthesized. Physical and chemical measurements (crystal structure, conductometry, IR and UV/VIS spectroscopy, and electrochemistry) were performed for 1, and these properties are compared with those presented by the kbPAPs active sites. Potentiometric titration studies of 1 have confirmed its acid/base properties that are crucial for the understanding of the phosphodiester and DNA catalytic cleavage in future studies.