Dynamer and Metallodynamer Interconversion: An Alternative View to Metal Ion Complexation

Authors:

• Anna Brzechwa-Chodzyńska,
• Michał Arkadiusz Zieliński,
• Mirosław Gilski,
• Jack M. Harrowfield,
• Artur Stefankiewicz

Abstract

A bifunctional molecule containing both a bidentate binding site for metal ions and an aminopyrimidine H-bond donor-acceptor site has been synthesized, and its properties, in its free and coordinated forms, have been established in solution and in the solid state by analytical and spectroscopic methods as well as by X-ray structure determinations. Structural characterization has shown that it forms a one-dimensional H-bonded polymeric assembly in the solid state, while spectroscopic measurements indicate that it also aggregates in solution. The reaction of a simple Fe(II) salt with this assembly results in the emergence of two geometrical isomers of the complex: [FeL₃](BF4)₂·9H₂O - C1 (meridional, mer) and [FeL₃]₂(SiF₆)(BF₄)₂·12H₂O - C2 (facial, fac). While, complex C1 in the solid state generates a one-dimensional H-bonded polymer involving just two ligands on each Fe center, with the chirality of the complex units alternating along the polymer chain, the structure of complex C2 shows NH···N interactions seen in both the ligand and mer complex (C1) structures to be completely absent. Physicochemical properties of the free and complexed ligand differ substantially.