An unprecedented class of benzoyldiazenido-functionalized polyoxometalates, [Bu4N]3[Mo6O18(=N=NCOAr)] (Ar=Ph, 1; Ph-o-Cl, 2; Ph-m-Cl, 3; Ph-p-Cl, 4; Ph-o,p-Cl2, 5; Ph-p-Br, 6; Ph-m-NO2, 7; Ph-p-NO2, 8; Ph-p-OMe, 9), are prepared through the reactions of α-octamolybdate and the corresponding hydrazides in dry acetonitrile under reflux with dicyclohexylcarbodiimide (DCC) as a dehydrating agent. Single-crystal X-ray diffraction structural analysis reveals that their anions demonstrate the typical structural features of monofunctionalized hexamolybdates with different organic substituents. 1H NMR spectroscopy indicates that the [Mo6O18(NN)] fragments in these compounds are electron-donating groups rather than electron-withdrawing groups, and this behaviour was further validated by the calculation of the atomic-charge distributions [natural bond orbital (NBO) and Mülliken]. Cyclic voltammetry (CV) indicates that they are more difficult to reduce than hexamolybdate and its organoimido derivatives. Antitumour activity tests against K562 show that most of the hybrid compounds have enhanced inhibitory activities compared with those of hexamolybdate and the corresponding hydrazide ligands.

Three new derivatives of hexavanadate with remote methacryl, phthalyl and tetrahydrophthalyl groups, respectively, were synthesized by esterification of pentaerythritol-derivatized hexavanadate. These new compounds were characterized by FT-IR, 1H NMR, UV-vis, elemental analysis and single-crystal X-ray diffraction. Their thermal stabilities were also tested by TGA analyses. Through such syntheses, we have successfully introduced the carbon–carbon double bond and/or carboxylic groups into the polyoxovanadates which could be utilized to build more complex structures. We also discuss the influence of anhydrides with different functional groups on the esterification of the pentaerythritol derivatized hexavanadate.

Three novel bis(Triol)-functionalized Anderson cluster derivatives (POM–L–POM, POM–L, L–POM–L) were efficiently synthesized, which manifest interesting self-assembly and synergistic effects. They provided strong support in synthons, applications in syntheses and properties for designing organic–inorganic hybrid chains.

A hexamolybdate-based organic–inorganic hybrid molecule containing a chloralkane fragment is synthesized and its Cl atom can be substituted by iodine and nitrate through nucleophilic substitution reactions in high yields, which provide a post-functionalization protocol to bring in various additional functional groups into polyoxometalate-based hybrid materials under mild conditions.

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 = MnIII (1), FeIII (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.

A series of remote hydroxyl functionalized organoimido derivatives of hexamolybdate, (Bu4N)2[Mo6O18(Cres)] (1) (Cres = 4-amino-m-cresol), (Bu4N)2[Mo6O17(Cres)2]·H2O (2), (Bu4N)2[Mo6O18(Phen)]·i-PrOH (Phen = p-aminophenol)(3), (Bu4N)2[Mo6O18(Phen)]·EtOH (4), (Bu4N)2[Mo6O17(Phen)2] (5), (Bu4N)2[Mo6O18(Naph)] (Naph = 5-amino-1-napheynyl) (6), and (Bu4N)2[Mo6O18(Chex)]·1.5H2O (Chex = trans-4-aminocyclohexanol) (7) were synthesized and characterized by single crystal X-ray diffraction, FT-IR spectra, UV−vis spectra, elemental analysis, 1H NMR, and cyclic voltammetry. X-ray structural study reveals that intermolecular and intramolecular hydrogen bonding plays an important role in their supramolecular assembly; it is found that (i) bridged oxo ligands of hexamolybdate cluster are more inclined to form hydrogen bonds as acceptors than terminal oxo ligands in this system; (ii) small solvent molecules with hydrogen bonding donor and acceptor, such as water, i-PrOH, and EtOH, usually act as hydrogen bonding bridge in their supramolecular assembly; (iii) hydrogen bonding has an important influence on their anion conformation besides cell packing; (iv) the hydrogen bonding supramolecular assembly of compounds 1−7 demonstrate an interesting change from dimer (3), to 1D infinite single chain (4), to 1D infinite double chain (2), and to 2D network (1, 5, 6, and 7) owing to the alteration of the grafting organic ligand, the substituted number, and the crystallized solvent molecule. To explore their potential application in conductivity, the optical band gap of compounds 1−7 were determined upon their solid state reflectance spectra. Our current study not only surveys systematically hydrogen bonding interaction and supramolecular assembly of remote hydroxyl functionalized organoimido-derivatized hexamolybdates but also provides some available precursors for further modification including esterification.

Three rigid-rod conjugated organic−inorganic hybrid nanodumbbells (Bu4N)4[O18Mo6N(C6H4)NMo6O18] (1), (Bu4N)4[O18Mo6N(C12H8)NMo6O18] (2), and (Bu4N)4[O18Mo6N(C14H12)NMo6O18] (3) bearing terminal polyoxometalate (POM) cages, with different lengths of approximately 2−3 nm and different substituents on the rod, have been synthesized via one-pot reaction of octamolybdate and the appropriate aromatic diamine dihydrochloride with N,N′-dicyclohexylcarbodiimide (DCC) as a dehydrating agent. These complexes have been characterized with UV−vis, IR, 1H NMR, ESI mass spectrometry, cyclic voltammetry, differential pulse voltammetry, and X-ray single-crystal diffraction techniques. The influence of the rod length and substituents on properties of these complexes has been investigated. In addition, the self-assembly of these nanorods has also been explored.

Three monofunctionalized organoimido derivatives of [Mo6O19]2− bearing an electron-withdrawing chloro group (R = p-ClC6H41, m-ClC6H42, or o-ClC6H43) have been prepared in high purity and moderate to good yields using an easy reaction route of [α-Mo8O26]4− with corresponding aromatic amine hydrochlorides or a mixture of aromatic amines and their hydrochloride salts in the presence of N,N′-dicyclohexylcarbodiimide (DCC). These complexes have been characterized by 1H NMR, IR, UV–Vis, UV–Vis-NIR reflectance spectroscopy, cyclic voltammetry, and their semiconductive and redox properties were explored by these techniques. Their electronic absorption spectra were also interpreted based on first-principles electronic structure calculations and these features of the simulated spectra are qualitatively consistent with the observed UV spectra. Additionally, the composition and structure of compounds 1 and 2 were further confirmed by X-ray single-crystal diffraction studies.Three chloro-functionalized organoimido substituted hexamolybdates, (Bu4N)2[Mo6O18(NR)], (R = p-ClC6H41, m-ClC6H42, or o-ClC6H43) were prepared in high purity and moderate to good yields using a convenient route of the reaction of [α-Mo8O26]4− with corresponding aromatic amine hydrochlorides or a mixture of aromatic amines and their hydrochloride salts in the presence of N,N′-dicyclohexylcarbodiimide with easy bench operation. Besides common structural characterization, their electronic absorption spectra were further interpreted based on first-principles electronic structure calculations.

Three novel bis(Triol)-functionalized Anderson cluster derivatives (POM–L–POM, POM–L, L–POM–L) were efficiently synthesized, which manifest interesting self-assembly and synergistic effects. They provided strong support in synthons, applications in syntheses and properties for designing organic–inorganic hybrid chains.

Three new derivatives of hexavanadate with remote methacryl, phthalyl and tetrahydrophthalyl groups, respectively, were synthesized by esterification of pentaerythritol-derivatized hexavanadate. These new compounds were characterized by FT-IR, 1H NMR, UV-vis, elemental analysis and single-crystal X-ray diffraction. Their thermal stabilities were also tested by TGA analyses. Through such syntheses, we have successfully introduced the carbon–carbon double bond and/or carboxylic groups into the polyoxovanadates which could be utilized to build more complex structures. We also discuss the influence of anhydrides with different functional groups on the esterification of the pentaerythritol derivatized hexavanadate.