Solvothermal Synthesis of Four Polyoxometalate-Based Coordination Polymers Including Diverse Ag(I)···π Interactions

Four 3D POM-based silver coordination polymers, namely, [Ag17(ptz)11(PW12O40)2]n (1), [Ag17(ptz)11(PMo12O40)2]n (2), [Ag12(ptz)6(CN)2(SiW12O40)]n (3), and [Ag19(ptz)8(H2ptz)­(H3ptz)­(AgP5W30O110)·7H2O]n (4), have been obtained by solvothermal reaction of AgNO3 and 5-phenyl-1H-tetrazole (Hptz) ligand in the presence of four types of polyoxometalates. Structural analysis shows that four types of Ag­(I)···π interactions, m-η1, m/p-η2, o/m-η2, and o/m/p-η3, were observed in compounds 1–4, depending on the polyoxometalates used. The in situ generated CN– ion in compound 3 shows unprecedented mixed σ and π bonding modes, similar to the C22‑ ion in well-studied silver acetylides. For 4, the Na+ ion in the Preyssler heteropolyoxoanion, [NaP5W30O110]14‑, was exchanged by Ag­(I) under solvothermal conditions, generating a novel [AgP5W30O110]14‑ anion. In addition, the photoluminescence behavior of 1–4 was also investigated.