Solution Studies and Crystal Structures of Heteropolynuclear Potassium/Copper Complexes with Phytate and Aromatic Polyamines: Self‐Assembly through Coordinative and Supramolecular Interactions

Phytate (L12−) is a relevant natural product. It interacts strongly with biologically relevant cations, due to the high negative charge exhibited in a wide pH range. The synthesis and crystal structures of the mixed‐ligand Cu(II) polynuclear complexes K(H2tptz)0.5[Cu(H8L)(tptz)] ⋅ 3.6H2O (1), K(H2O)3{[Cu(H2O)(bpca)]3(H8L)} ⋅ 1.75H2O (2), and K1.5(H2O)2[Cu(bpca)](H9.5L) ⋅ 8H2O (3) (tptz=2,4,6‐tri(pyridin‐2‐yl)‐1,3,5‐triazine; Hbpca=bis(2‐pyridylcarbonyl) amine) are reported herein. They were obtained by the use of an aromatic rigid amine, which satisfies some of the metal coordination sites and promotes the hierarchical assembly of 2D polymeric structures. Speciation of phytate−Cu(II)−Hbpca system and determination of complex stability constants were performed by means of potentiometric titrations, in 0.15 M NMe4Cl at 37.0 °C, showing that, even in solution, this system is able to produce highly aggregated complexes, such as [Cu3(bpca)3(H7L)]2−. Furthermore, the Cu(II)‐mediated tptz hydrolysis was studied by UV‐vis spectroscopy at room temperature in 0.15 M NMe4Cl. Based on the equilibrium results and with the aid of molecular modelling tools, a plausible self‐assembly process for 2 and 3 could be proposed. Solid construction: Polynuclear Cu2+ complexes are formed between the naturally occurring phytate molecule and aromatic amines in aqueous solution. In the solid state, coordination and noncovalent interactions cooperate in the formation of 2D polymeric assemblies. Phytate forms the backbone of the polymers through coordinative bridging interactions with metal ions (K+, Cu2+), while π‐π stacking between the auxiliary aromatic ligands completes the 2D structures.