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A bottom-up approach to obtain nanoclusters and large, uniform vesicle-like structures containing organic functionalized hexamolybdates in solution state were developed. Hexamolybdate functionalized carboxylic acid coordinated with two copper ions to form paddle-wheel tetrapolyoxometalate clusters with the features of macro-ions, which can spontaneously assemble into large, stable blackberry-type structures in suitable solvents, completing a hierarchical organization from small POM molecules to nanoscale complexes and then to supramolecular structures.

Two rod-shaped macroanions, ((C4H9)4N)7[Mo6O18NC(OCH2)3XMo6O18(OCH2)3CNMo6O18] (X = Mn(III) (1), Fe(III) (2)), with almost identical charge densities and morphologies except for their different encapsulated central metal atoms were each observed to self-assemble into "blackberry"-type supramolecular structures in their dilute solution, driven by the counterion-mediated attraction. Amazingly, the two macroions remained self-sorted and self-assembled into homogeneous assemblies in their mixed solutions, demonstrating a self-recognition behavior between two highly similar macroions during their assembly process, as confirmed by DLS, SLS, and TEM/EDS analysis. This self-recognition behavior can be explained by the slightly different charge distributions of the macroanions resulting from their different central atoms (confirmed by theoretical DFT calculations and dissociation experiments) and the high activation energy of the slow assembly process, which suppresses the formation of hybrid oligomers at the beginning of the self-assembly process. This work confirms that the long-range counterion-mediated electrostatic attraction is sensitive to the small difference in macroions and consequently offers the possibility for delicate selectivity and preference among different macroions. This phenomenon might be directly related to (and be the important reason for) some recognition behaviors in biological systems.

The assembly of two achiral POMs of Lindqvist and Anderson through strong covalent linkages, using bifunctional TRIS with a rotatable C-N single bond, gives two nanoscale rod-like chiral molecular triads with C(2) symmetry, the chirality of which were confirmed by the single crystal X-ray diffraction analyses and solid CD spectroscopy measurements. The enantiopure crystals of these compounds have been obtained by spontaneous resolution upon crystallization in the absence of any chiral source. The present work opens a way to make chiral nanostructures from achiral polyoxoanions, which may have potential applications in asymmetric catalysis, NLO, and ferroelectric materials.

In this communication, we demonstrate that polyoxomolybdates can activate sp3 C−H bonds in aliphatic amines. Unexpectedly, a carbon−carbon double bond is formed from two aliphatic primary amines via the activation and dehydrogenative coupling of two sp3 C−H bonds near the nitrogen atom bearing a hexamolybdate. Detailed experiments including 1H NMR, 13C NMR, IR, UV−vis, ESI-MS, and especially X-ray single-crystal diffraction substantially confirm the existence of carbon−carbon double bonds in a class of so-resulting organic−inorganic hybrid molecules, which are made up of two terminally substituted imidohexamolybdate cages bridged by a trans-tetrasubstituted, conjugated, rigid ethylene system. This discovery perhaps opens an interesting road to elaborate the CC double bond directly via the functionalization of saturated C−H bonds.