Deeply Reduced Chiral Mo-Polyoxometalates with Highly Enhanced Electronic Conductivity.

A series of deeply reduced Mo-polyoxometalates (POMs), [Mo(bpy)MoOS]·10HO () (bpy = 2,2'-bipyridine), [Mo(bpy)(L-TrA)Mo(bpy)OS]·36.5HO (), and [Mo(bpy)(D-TrA)Mo(bpy)OS] () (TrA = tartaric acid), were obtained from one-pot hydrothermal syntheses. They feature the bioxo-bridged [MoOS] incomplete cuboidal cores stabilized by strong triangular metal-metal bonds and datively chelated bpy π-ligands. The two apical MoO in 12e-Mo () and two [MoOSTrAbpy] in 16e-Mo (, ) complete the octahedral coordination geometry of the deeply reduced Mo, not counting the Mo-Mo d-d bonds. The aromatic planar bpy π ligands form a two-dimensional face-to-face π stacking supramolecular structure, which are further strengthened by point-to-face C-H···π interactions in the π stacked layers. 16e-Mo () has stronger intramolecular face-to-face π stacking interactions, which are interconnected by intermolecular C-H···π into a three-dimensional framework structure. These structural features account for their highly enhanced electronic conductivities (, 6.19 × 10 S cm; , 2.18 × 10 S cm), providing a new way of thinking to improve electronic conductivity of POMs. - have been described by first-principles density function theory (DFT) calculations and also characterized by elemental analyses, powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), solid UV-visible spectra, and circular dichroic (CD) spectra.