The synthesis of anisotropic redox-active polyoxometalates (POMs) that can switch between multiple states is critical for understanding the mechanism of assembly of structures with a high aspect ratio, as well as for their application in electronic devices. However, a synthetic methodology for the controlled growth of such clusters is lacking. Here we describe a strategy, using the heteroanion-directed assembly, to produce a family of 10 multi-layered, anisotropic POM cages templated by redox-active pyramidal heteroanions with the composition [W 16 Mo 2 O 54 (XO 3 )] n − , [W 21 Mo 3 O 75/76 (XO 3 ) 2 ] m − , and [W 26 Mo 4 O 93 (XO 3 ) 3 ] o − for the double, triple, and quadruple layered clusters, respectively. It was found that the introduction of reduced molybdate is essential for self-assembly and results in mixed-metal (W/Mo) and mixed-valence (W VI /Mo V ) POM cages, as confirmed by an array of analytical techniques. To probe the archetype in detail, a tetrabutyl ammonium (TBA) salt derivative of a fully oxidized two-layered cage is produced as a model structure to confirm that all the cages are a statistical mixture of isostructures with variable ratios of W/Mo. Finally, it was found that multilayered POM cages exhibit dipolar relaxations due to the presence of the mixed valence W VI /Mo V metal centers, demonstrating their potential use for electronic materials.

The electrical conductivity of mixed-valence [MoMoO(SO)] tetraalkylammonium salts was investigated through dependence on the inter-cluster distance that is controlled by tetraethylammonium, tetrapropylammonium, and tetrabutylammonium cations. The crystallographic analysis of single crystals revealed that the inter-cluster distances are dependent on the chain length of the alkyl groups on the counter cations. In addition, the electrical conductivities of the single crystals were found to be dependent on both temperature and chain length. Mixed-valence polyoxometalate (POM) clusters are considered to be a molecular particle of Mo bronze by which highly ordered networks will be developed using single crystals, where POMs are rather small and have a well-organized structure compared to colloidal nanostructures.

Ionic single crystals of the polyoxometalate [Mo V 2 Mo VI 16 O 54 (SO 3 ) 2 ] 6salted with tetrabutylammonium were found to exhibit dielectric anomalies at 235 and 302 K. The clear DSC peak at 235 K indicates the first-order nature of transition. The next transition at 302 K was concluded to be secondorder in nature, demonstrating the existence of three different phases (α, , and γ). Temperature-dependent single-crystal X- [a]

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.

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.