Self-Assembly of Manganese(II)–Phytate Coordination Polymers: Synthesis, Crystal Structure, and Physicochemical Properties

Myo-inositol phosphates are an important group of biomolecules present in all eukaryotic cells. The most abundant member of this family in nature is InsP6 (phytate, L12− in its fully deprotonated form). Phytate interacts strongly with inorganic and organic cations, and this interaction is essential for determining the possible functions of this biomolecule. We present here the chemical, thermodynamic and structural characterization of phytate-Mn(II) species in a contribution to understand how the interaction of both components modulates their biological roles and their bioavailability. Polynuclear complexes Mn5(H2L)·16H2O (1) and (H2terpy)2[Mn(H6L)(terpy)(H2O)]·17H2O (terpy = terpyridine) (2) were prepared and characterized by different techniques. The isolation of 1, and the determination of its solubility, together with potentiometric titrations of the Mn(II)-phytate system allowed the full description of this binary systems. The preparation and crystal structure of 2 shows a novel coordination mode of phytate, the formation of infinite polymeric chains through equatorial phosphate groups.