Charge-Assisted Hydrogen-Bonded Assemblage of an Anionic {M(C2O4)4}4- Building Unit and Organic Cations: A Versatile Approach to Hybrid Supramolecular Architectures

The possibility to construct extended hybrid hydrogen-bonded networks by association of an anionic coordination complex and organic cations acting respectively as a hydrogen-bond acceptor and hydrogen-bond donors is explored. A series of seven architectures developed by charge-assisted hydrogen-bond association of {Zr(C2O4)4}4- (C2O4 = oxalate) and dications bearing N−H donor functions are described. The selected organic modules (i.e., protonated 4,4‘-bipyridine, di(4-pyridyl)ethane, di(4-pyridyl)ethylene, piperazine, m/p-phenylenediamine, terephtalamidine) possess two hydrogen-donor functions to allow them to act as bridges between the inorganic anions. Depending on the nature of the donor group, the number of hydrogens available for bonding, the geometric features, and sizes of the organic modules diverse assembling patterns have been observed ranging from one-dimensional (1-D) to three-dimensional (3-D) interlocked networks. A further, rather surprising hybrid system was realized by assembling the inorganic anion with 4,4‘-bypiridine-N,N‘-dioxide in acidic medium. For the latter, H3O+ and H+ act as actual linkers between the molecular units. The crystal structures for all eight supramolecular architectures as well as their thermal stabilities are reported.