First Organic–Inorganic Hybrid Compounds Formed by Ge-V-O Clusters and Transition Metal Complexes of Aromatic Organic Ligands

Three compounds based on Ge-V-O clusters were hydrothermally synthesized and characterized by IR, UV-Vis, XRD, ESR, elemental analysis and X-ray crystal structural analysis. Both [Cd(phen)(en)]2[Cd2(phen)2V12O40Ge8(OH)8(H2O)]∙12.5H2O (1) and [Cd(DETA)]2[Cd(DETA)2]0.5[Cd2(phen)2V12O41Ge8(OH)7(0.5H2O)]∙7.5H2O (2) (1,10-phen = 1,10-phenanthroline, en = ethylenediamine, DETA = diethylenetriamine) are the first Ge-V-O cluster compounds containing aromatic organic ligands. Compound 1 is the first dimer of Ge-V-O clusters, which is linked by a double bridge of two [Cd(phen)(en)]2+. Compound 2 exhibits an unprecedented 1-D chain structure formed by Ge-V-O clusters and [Cd2(DETA)2]4+ transition metal complexes (TMCs). [Cd(en)3]{[Cd(η2-en)2]3[Cd(η2-en)(η2-μ2-en)(η2-en)Cd][Ge6V15O48(H2O)]}∙5.5H2O (3) is a novel 3-D structure which is constructed from [Ge6V15O48(H2O)]12− and four different types of TMCs. We also synthesized [Zn2(enMe)3][Zn(enMe)]2[Zn(enMe)2(H2O)]2[Ge6V15O48(H2O)]∙3H2O (4) and [Cd(en)2]2{H8[Cd(en)]2Ge8V12O48(H2O)}∙6H2O (5) (enMe = 1,2-propanediamine), which have been reported previously. In addition, the catalytic properties of these five compounds for styrene epoxidation have been assessed.

Ordnung muss sein: heteroelement order and disorder in polyoxovanadates

Three new mixed antimonato–germanato polyoxovanadates exhibit different degrees of order of their unique crystallographic heterometal atom positions.

Catalysis of "outer-phase" oxygen atom exchange reactions by encapsulated "inner-phase" water in {V15Sb6}-type polyoxovanadates

A water molecule encapsulated inside water-soluble {V₁₅Sb₆} antimonato polyoxovanadate cages accelerates oxygen-exchange reactions in the cluster periphery.

Antimonato polyoxovanadate (POV) cluster compounds {M(en)₃}₃[V₁₅Sb₆O₄₂(H₂O)_x]·nH₂O (M = Fe^II, Co^II, Ni^II and x = 0 or 1) obtained under solvothermal conditions exhibit unusual high water solubility making these compounds promising synthons for generation of new POV structure types. Electrospray ionization mass spectrometry provides evidence (i) for a water molecule encapsulated inside the cavity of a fraction of the spherical cluster shells, (ii) for a post-functionalization in water, namely a slow exchange of VO against Sb₂O, (iii) for the inner-phase reactivity of the encapsulated water that is capable of opening an oxo-bridge, and (iv) for a significant acceleration of the ¹⁶O/¹⁸O exchange reactions of oxygen atoms in the cluster periphery with surrounding H₂¹⁸O, when encapsulated water is present. To the best of our knowledge, this is the first example in polyoxovanadate chemistry for the transduction of inner-phase reactivity of an encapsulated guest molecule into changes in the outer-phase reactivity of the cluster. Magnetic susceptibility measurements reflect the individual contributions of the frustrated {V₁₅} spin polytope and the {M(en)₃}²⁺ complexes, with very weak coupling between these groups.

Supramolecular hexagonal nano tubes assembled by vanadium diamine complexes with thiogermanates

A supramolecular hexagonal nano tube is characterized, which is assembled by oxo-vanadium thiogermanate in a sulfur–diamine reduction system.

Semimetal-functionalised polyoxovanadates

Polyoxovanadates (POVs), known for their wide applicability and relevance in chemical, physical and biological sciences, are a subclass of polyoxometalates and usually self-assemble in aqueous-phase, pH-controlled condensation reactions. Archetypical POVs such as the robust [VO42](12-) polyoxoanion can be structurally, electronically and magnetically altered by heavier group 14 and 15 elements to afford Si-, Ge-, As- or Sb-decorated POV structures (heteroPOVs). These main-group semimetals introduce specific chemically engineered functionalities which cause the generally hydrophilic heteroPOV compounds to exhibit interesting reactivity towards organic molecules, late transition metal and lanthanoid ions. The fully-oxidised (V(V)), mixed-valent (V(V)/V(IV) and V(IV)/V(III)), "fully-reduced" (V(IV)) and "highly-reduced" (V(III)) heteroPOVs possess a number of intriguing properties, ranging from catalytic to molecular magnet characteristics. Herein, we review key developments in the synthetic and structural chemistry as well as the reactivity of POVs functionalised with Si-, Ge-, As- or Sb-based heterogroups.

Polyoxometalate-directed assembly of various multinuclear metal–organic complexes with 4-amino-1,2,4-triazole and selective photocatalysis for organic dye degradation

Five POM-based metal–organic complexes ranging from 0D trinuclear cluster, 1D chain, 2D network, to 3D framework have been successfully prepared in the presence/absence of citric or boric acid.

Two tetra-Cd(II)-substituted vanadogermanate frameworks

Two new tetra-Cd(II)-substituted vanadogermanate frameworks {(CdX)4Ge8V(IV)10O46(H2O)[V(III)(H2O)2]4(GeO2)4}·8H2O (X = ethylenediamine (en, 1) and 1,2-diaminopropane (dap, 2)) were hydrothermally prepared and characterized by IR spectra, elemental analysis, powder X-ray diffraction (PXRD), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and X-ray single-crystal diffraction. Both are isomorphic, and their 3-D frameworks are made up of tetra-Cd(II)-substituted {(CdX)4Ge8V(IV)10O46(H2O)}(12-) fundamental building units interconnected through planar tetra-V(III) [V(III)4O2(H2O)8](8-) clusters and tetrahedral GeO4 bridges. In the unique {(CdX)4Ge8V(IV)10O46(H2O)}(12-) cage, four [Ge2O7] dimers and four CdO4N2 trigonal prisms are alternately concatenated by μ3-O bridges to create a round {Ge8Cd4O28(X)4}(16-) fragment, five VO5 groups are linked by sharing edges to generate a pentanuclear [V5O17] subunit, and then the {Ge8Cd4O28(X)4}(16-) fragment is sandwiched by two V5O17 subunits via sharing O-atoms producing a D4h-symmetric {(CdX)4Ge8V(IV)10O46(H2O)}(12-) cage with a free water molecule located at the center. As we know, both display unprecedented 3-D organic-inorganic hybrid frameworks built up from the largest number of transition-metal-substituted vanadogermanate {(CdX)4Ge8V(IV)10O46}(12-) cluster shells linked by both GeO4 tetrahedra and rare [V(III)4O2(H2O)8](8-) clusters. Magnetic measurements reveal the antiferromagnetic couplings within the magnetic vanadium centers.