Design and analysis of chain and network structures from organic derivatives of polyoxometalate clusters

Polyoxometalate (POM) clusters derivatized with aniline groups exhibit distinct interactions with counterions and with each other. These interactions lead to the assembly of the clusters into chains and networks upon crystallization. Two cluster types were examined, (W₆O₂₅H(AsC₆H₄ -4-NH₂)₂]^5- and (Mo₁₂O₄₆(AsC₆H₄-4- NH₂)₄]^4-. The X-ray crystal structures were solved for the mixed salts containing [C(NH₂)₃]⁺/Na⁺, Ag⁺/H⁺, or Cu²⁺/H⁺ as counterions. The X-ray crystal structures reveal that the POM clusters are linked together by hydrogen bonds or POM-metal ion-POM linkages. The roles of the counterions, solvents, and organic groups in the formation of specific crystalline architectures are discussed. Strongly interacting counterions form bonds to the oxo ligands of the POM and connect them into tetrameric units and/or into one-dimensional chains. The hydrogen bonding strength of the solvent influences the formation of hydrogen bonds between the aniline groups and oxo ligands of the cluster. The aniline groups played differing roles in the final structures: they were either nonbonding, bonded to a counterion, or involved in hydrogen bonding. Depending on the bonding interactions, the architecture of the cluster salts may be significantly altered.