Assembly of organic-inorganic hybrid supramolecular materials based on basketlike {M⊂P6Mo18O73} (M = Ca, Sr, Ba) cage and transition-metal complex.

Eight members of basketlike mixed-valent compounds, formulated as {H(3)O}(2){Fe(III)(2,2'-bpy)(3)}(6){Sr⊂P(6)Mo(V)(4)Mo(VI)(14)O(73)}(2)·9H(2)O (1), {H(2)(4,4'-bpy)}(5){Ni(4,4'-bpy)(H(2)O)(3)[Ni(H(2)O)(2)]Sr⊂P(6)Mo(V)(2)Mo(VI)(16)O(73)}·12H(2)O (2), {Cu(2)(bim)(4)(H(2)O)}(2){Cu(bim)(2)Cu(bim)(H(2)O)Cu(H(2)O)(2)Sr⊂P(6)Mo(V)(3)Mo(VI)(15)O(73)}·16H(2)O (3), {H(3)O}(4){Cd(phen)(2)Sr(H(2)O)(5)[Sr⊂P(6)Mo(V)(4)Mo(VI)(14)O(73)]}·H(2)O (4), {Cu(bim)(2)} {Cu(bim)(2)[Cu(Hbim)(H(2)O)(2)][Ca⊂P(6)Mo(V)(3)Mo(VI)(15)O(73)]}·9H(2)O (5), {Cu(2,2'-bpy)(H(2)O)[Ca⊂P(6)Mo(V)(2)Mo(VI)(16)O(73)]}·4H(2)O (6), {Cu(2,2'-bpy)(H(2)O)[Sr⊂P(6)Mo(V)(2)Mo(VI)(16)O(73)]}·8H(2)O (7), and {Cu(2,2'-bpy)(H(2)O)[Ba⊂P(6)Mo(V)(2)Mo(VI)(16)O(73)]}·8H(2)O (8), have been hydrothermally synthesized and structurally characterized via elemental analysis, thermogravimetry (TG), infrared (IR) spectroscopy, ultraviolet-visible light (UV-vis) spectroscopy, X-ray photoelectron spectroscopy (XPS), and single-crystal X-ray diffraction (XRD). The structural analysis shows that all the compounds contain basket-shaped polyoxoanions M⊂P(6)Mo(V)(n)Mo(VI)(18-n)O(73) (M = Ca, Sr, Ba; n = 2, 3, or 4) (abbreviated as {P(6)Mo(18)O(73)}) as building units, which consists of a tetravacant γ-Dawson-type{P(2)Mo(14)} unit and a "handle"-shaped {P(4)Mo(4)} segment encapsulating a single alkaline-earth metals cation M(2+) in the central cavity. Compound 1 presents a zero-supported basketlike structure decorated by three discrete {Fe(2,2'-bipy)(3)} fragments. Compound 2 is monosupported by {Ni(4,4'-bipy)(H(2)O)(3)} subunit. Compound 3 and 4 are bisupported by copper complexes and cadmium complexes, respectively. Compound 5 exhibit a trisupported basket cluster modified with two {Cu(bim)(2)}(2+) and one {Cu(Hbim)(H(2)O)}(3+) cations. Compounds 6-8 are isostructural clusters exhibiting similar tetra-supported structures. Compound 1, 2, and 4 represent the first basket-like hybrids containing transition-metal iron, nickel, and cadmium, respectively. In addition, compounds 2, 6, 7, and 8 are observed for the first time as a two-electron-reduced basket form. The compounds display good electrocatalytic activity upon the reduction of nitrite, and fluorescent properties.