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.