Assembly of polyoxometalate-based inorganic-organic compounds from silver-Schiff base building blocks: synthesis, crystal structures and luminescent properties

Three polyoxometalate-based inorganic-organic hybrid compounds constructed from silver(I)-L (L = N,N'-bis-pyridin-2-ylmethylene-hydrazine) species and saturated Keggin type polyoxoanions, {[Ag3L3] (PW12O40)(CH3CN)(DMF)(2.5)}(n) (1), [Ag4L3(CH3CN)(4)][Ag2L(CH3CN)(3)](PMo12O40)(2)center dot CH3CN (2) and [(SiMo12O40){Ag2L(CH3CN)(3)}(2)]center dot(CH3CN)(2) (3), have been synthesized and structurally characterized by IR spectroscopy, UV spectroscopy, thermogravimetric (TG) analyses and complete single crystal structure analyses. The structure of 1 containing [PW12O40](3-) anions as templates exhibits a one-dimensional chain structure constructed by the coordination of a silver center and bis-bidentate bridging ligands with the pyridyl rings adopting a transoid configuration. Compound 2 displays an AB-type arrangement supramolecular structure, in which A is a two-dimensional sheet formed by linking the adjacent [Ag4L3(CH3CN)(4)](4+) units through the cooperativity of intermolecular pi-pi interactions and C-H center dot center dot center dot pi interactions, while B is composed of [PMo12O40](3-) anions and binuclear [Ag2L(CH3CN)(4)](2+) cations. Compound 3 exhibits a new bisupporting Keggin-polyoxometalate structure in which the [SiMo12O40](4-) core supports two [Ag2L(CH3CN)(3)](2+) fragments in two opposite positions. The luminescent properties of L and 1-3 in the solid state were investigated.