Self-Assembly of Anionic Polyoxometalate–Organic Architectures Based on Lacunary Phosphomolybdates and Pyridyl Ligands

The development of
novel systems for metal–organic architectures
is an attractive research field because they are fascinating materials
with unexplored functions. Lacunary polyoxometalates (POMs) offer
structurally well-defined coordination sites with various coordination
directions and numbers in addition to the designable properties; thus,
lacunary POMs are ideal building blocks for inorganic–organic
architectures. However, their utilization is currently limited by
their low stability and difficulty in controlling the reactivity.
Here, we report the successful self-assembly of anionic POM–organic
architectures comprising multivacant lacunary POMs and pyridyl ligands.
By introducing pyridine moieties to its vacant sites, the trivacant
lacunary phosphomolybdate [A-α-PMo9O34]9– is significantly stabilized in organic solvents.
Furthermore, the resultant structure can be utilized as a stable and
reactive building block to synthesize a dimer pillared by 4,4′-bipyridyl
and a tetramer bridged by two cofacial porphyrin ligands, which can
intercalate aromatic molecules.