Syntheses, structures and luminescent properties of six divalent metal terephthalate coordination polymers based on three new flexible bis(imidazole) ligands

Six coordination polymers based on terephthalate and one of three new symmetry-related ligands which contain two flexible -O-CH2-CH2- chains connecting two imidazole-derived groups to a rigid naphthalene ring (2,7-bis(ethoxyimidazole)-naphthalene (L1), 2,7-bis(ethoxybenzimidazole)-naphthalene (L2), 1,5-bis(ethoxybenzimidazole)-naphthalene (L3)), formulated as [Cd(L1)(p-bdc)]center dot DMF center dot H2O (1), [Co(L1)(p-bdc)(H2O)(2)]center dot H2O (2), [Zn-2(L1)(2)(p-bdc)(2)]center dot 3H(2)O (3), [Zn(L2)(p-bdc)]center dot DMF (4), [Co(L2)(p-bdc)]center dot H2O (5), [Co(L3)(p-bdc)(H2O)]center dot 2DMF (6), have been prepared under hydrothermal conditions. Compound 1 shows a two-dimensional (2D) (4(4))-network with a 2-fold interpenetration structure. Compound 2 possesses a three-dimensional (3D) framework and can be simplified as a qzd (quartz-dual) "dense" net with point (Schlafli) symbol {7(5).9}. Compound 3 displays an infinite one-dimensional (1D) structure containing three different rings, exhibiting a "cryptand ring" structure. Compound 4 presents a 2D framework and exhibits slightly undulating (4(4)) topology. Compound 5 exhibits a 2D network with point (Schlafli) symbol {12}{4.12(5)}{4}. Compound 6 demonstrates a 2D network with point (Schlafli) symbol {8(4).12(2)}{8}(2). A comparison of the six complexes shows that the coordination mode of the terephthalate plays a key role in the construction of the coordination polymers and the three N-containing ligands beautify and enrich the structures. In addition, the powder X-ray diffraction (PXRD), elemental analysis, IR, thermal stability and optical properties of all compounds were investigated.