Seven organic–inorganic hybrid compounds constructed from 2,4,6-tris-(pyridyl)-1,3,5-triazine and polyoxometalates

Seven new organic–inorganic hybrid compounds containing inorganic polyoxometalates and trigonal organic ligand 2,4,6-tris-(3/4-pyridyl)-1,3,5-triazine (3/4-tpt), namely [Mo8O26M(Htpt)2(H2O)2]n (M = Zn (1), Co (2), Ni (3)), [Mo8O26Cu(Htpt)2(H2O)2]n·2nH2O (4), [Mo8O26(H2tpt)2]·6H2O (5), [Mn(Mo4O13)(4-tpt)2]n (6) and [Fe3(Mo4O15)(3-tpt)]n·nH2O (7), were synthesized hydrothermally and characterized by EA, IR, TG, and PXRD techniques. Single crystal X-ray structural analysis revealed that compounds 1–4 are 1-D coordination polymers constructed from [Mo8O26]4− cluster and [M(Htpt)2(H2O)2]4+ fragments. Compound 5 is an isolated cluster composed of [Mo8O26]4− anion and monodentate H2tpt2+ cation. 3-Tpt ligands in 1–5 are partially protonated and act as monodentate ligands. Octamolybdates adopt β- and γ-[Mo8O26]4− structural mode in compounds 1–4 and 5, respectively. In compound 6, each [Mo4O13]2− tetramer links four Mn(II) ions to form a 2-D wave-like polymeric layer. The 2-D [MnMo4O13] bimetallic layers are pillared by neutral 4-tpt bidentately to generate a 3-D metal–organic framework. Compound 7 is a 3-D coordination polymer constructed from 2-D [Fe3(Mo4O15)] bimetallic polymeric layer and pillared by neutral tridentate 3-tpt. These compounds are thermal stable under 250 °C. The compounds 1 and 5 display luminescence with emission maximum at 481 and 442 nm, respectively.