pH-Dependent syntheses and crystal structures of a series of organic-inorganic hybrids constructed from Keggin or Wells-Dawson polyoxometalates and silver coordination compounds.

A series of silver complexes of polyoxometalates (POMs), formulated as, [Ag(2)(4,4'-bpy)(2)(4,4'-Hbpy)(H(2)O)][PW(12)O(40)] (4,4'-bpy = 4,4'-bipyridine, 1), [Ag(4)(4,4'-bpy)(4)][4,4'-H(2)bpy][P(2)W(18)O(62)].4H(2)O (2), [Ag(4)(4,4'-bpy)(4)][H(2)P(2)W(18)O(62)].7H(2)O (3), and Na(8)[Ag(3)(4,4'-bpy)(3)][PW(10)Ag(2)O(39)].6H(2)O (4), have been hydrothermally synthesized in situ at different pH. Complex 1, based on saturated Keggin POM building blocks and silver coordination compounds, exhibits an interesting 3-fold interpenetration of diamondlike network in the POM chemistry. Different from complex 1, complexes 2-3 consist of Wells-Dawson polyoxoanions and silver coordination compounds. Complex 2 represents the highest coordination number of Wells-Dawson polyoxoanions, which helps to form a high-dimensional framework with (4.6(4).8)(4)(4(4).6(16).8(8)) topology. Thee-dimensional (3D) Wells-Dawson phosphotungstate 3 reveals another new topology (4.6(4).7)(4.6(4).8)(2)(4(3).6(8).7(2).8(2)). Complex 4 forms a 3D framework constructed from divacant Keggin polyoxoanions and silver coordination compounds. Their structural differences indicate that the pH value of the reaction system plays a key role on the structures and topologies of these complexes, and the whole self-assembly process is pH-dependent.