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

Abstract

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·CH₃CN (2) and [(SiMo₁₂O₄₀){Ag₂L(CH₃CN)₃}₂]·(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 π–π interactions and C–H⋯π 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.