Synthesis and Characterization of 2D and 3D Structures from Organic Derivatives of Polyoxometalate Clusters: Role of Organic Moiety, Counterion, and Solvent

New organic derivatives of “inverse-Keggin” polyoxometalate (POM) clusters, [Mo12O46(AsR)4]4- (R = C6H4-4-COOH, C6H3-4-OH-3-NO2, C6H4-4-OH), have been synthesized. Structures of the corresponding sodium or
iron salts were elucidated by single-crystal X-ray diffraction and shown to be 3D structures connected through
hydrogen bonds and/or O−Na−O linkages. Parameters which influence the final solid-state architecture, such as
the crystallizing solvent, organic moiety, and counterions, have been examined. The hydrogen-bonding ability of
the solvent affects the connectivity of the POM clusters through interactions with the organic group and the
inorganic core. The organic groups influence the structure through hydrogen bonds to other organic groups, to
neighboring clusters, and/or to solvent molecules. Hydrogen bonding between the organic groups and the solvent
appears to inhibit some possible connectivity patterns, such as the hydrogen-bonded dimerization of carboxylic
acid groups. Na+ ions were found directly bonded to the cluster oxo ligands and provided linkages between
clusters. Larger cations, such as transition metals, did not show this interaction, and other bonding methods
dominated.