Effect of pH/metal ion on the structure of metal–organic frameworks based on novel bifunctionalized ligand 4′-carboxy-4,2′:6′,4′′-terpyridine

Four novel coordination polymers, [Cd2(ctpy)4]n·2nH2O (1), [Cd2(ctpy)2(ox)]n (2), [Zn(ctpy)(ox)0.5]n·0.5nH2O (3) and [Cu2(ctpy)2(ox)]n (4), (Hctpy = 4′-carboxy-4,2′:6′,4′′-terpyridine H2ox = oxalic acid), have been hydrothermally synthesized and characterized by elemental analysis, IR, single crystal X-ray diffraction and thermogravimetric analyses. Compound 1 is a new two-fold interpenetrating (3,5)-connected 3D framework with Schläfli symbol (63)(69·8). Compound 2 displays an unusual three-dimensional coordination network which exhibits an intriguing (4,5)-connected binodal new topological net with Schläfli symbol (42·63·8)(42·65·83). Compound 3 features a two-fold interpenetrating (3,4)-connected 3D framework with the fsc topological net and the Schläfli symbol (63)(65·8). Compound 4 is a three-fold interpenetrating (3,4)-connected 3D framework with dmc topological net and Schläfli symbol (4.82)(4.85). Interestingly, compounds 1–4 were obtained under similar reaction conditions. The structural diversity of compounds 1 and 2 may illustrate the marked effect of pH on the reaction solution. And the diversity structures of the compounds 2–4 may illustrate the marked effect of the metal ion on the reaction solution. Moreover, the fluorescent property of compounds 1–3 as well as the adsorption properties of 3 are also investigated.