POLYMORPHISM OF TETRAZOLE AND MAGNESIUM-BASED HYDROGEN BONDED FRAMEWORKS

Tetrazoles have attracted much interest as effective bridging ligands for multi-dimensional metal- organic frameworks, due to their potential function as strong σ-electron donors to metals and their diverse possible modes of coordination. In addition, the N and NH sites of the multi-dentate tetrazole moiety can serve as either donors or acceptors in strong hydrogen bonding interactions with complimentary partners. Correspondingly, crystalline solids of tetrazole-based compounds reveal oftentimes 2D and 3D supramolecular networking supported by arrays of intermolecular hydrogen bonds.

Herein we present three polymorphic supramolecular aggregates of Mg(H₂O)₆ with bis(tetrazole) in an aqueous environment. Instead of the anticipated coordination-framework products, hydrogen bonded periodic frameworks of different architectures have been formed. The crystal structures and hydrogen bonding patterns of the polymorphic forms will be discussed, along with characterizations of their thermal stability.