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Abstract
The fabrication of redox-active polyoxometalates (POMs)
that can switch between multiple states is critical for their application
in electronic devices, yet, a sophisticated synthetic methodology is
not well developed for such cluster types. Here we describe the
heteroanion-directed and reduction-driven assembly of a series of
multi-layered POM cages 1-10 templated by 1-3 redox-active
pyramidal heteroanions. The heteroanions greatly affect the selfassembly of the resultant POM cages, leading to the generation of
unprecedented three-layered peanut-shaped - 4, 7 and 8 - or bulletshaped - 5 and 6 - structures. The introduction of reduced
molybdate is essential for the self-assembly of the compounds and
results in mixed-metal (W/Mo), and mixed-valence (WVI/MoV) 1-10,
as confirmed by redox titration, UV-Vis-NIR, NMR spectroscopy and
mass spectrometry. 11, the tetrabutyl ammonium (TBA) salt
derivative of the fully oxidized 3, is produced as a model structure for
measurements to confirm that 1-10 are a statistical mixture of
isostructural clusters with different ratios of W/Mo. Finally, multilayered POM cages exhibit dipole relaxations due to the presence of
mixed valence WVI/MoV metal centers, demonstrating their potential
uses for electronic materials.
