Tuning structural topologies of five photoluminescent Cd(II) coordination polymers through modifying the substitute group of organic ligand

Five new Cd(II) coordination polymers based on mixed 5-position substituted 1,3-benzenedicarboxylate ligands (R=-NO2/-OH/-CH3) and 1,4-bis(imidazol-1-yl)benzene (Li)or 1,4-bis(1-imidazol-yl) 2,5- dimethyl benzene (L-2), namely [Cd(5-NO2-iP)(L-1)center dot H2O] (1), [Cd(5-OH-ip)(L-1)](n) (2), [Cd(5-NO2-iP) (11)(0.5)(H2O)(2)](5) (3), {[Cd(5-NO2-iP)(L2)(0.5)(H2O)center dot H2O} (4), [Cd(5-CH3-ip)(L-2)(H2O)(2)](n), (5), have been synthesized hydrothermally and structurally characterized. With different substituted groups in the organic ligands, five compounds exhibit five distinct framework structures. By changing the pH value, compound 1 with 2-fold interpenetrating (4,4)-layer structure and compound 3 with three-dimensional diamond-type framework are obtained, respectively, from the assembly of Cd(NO3)(2). 4H(2)O, 5-NO2-ip and L-1 ligand. The replacement of 5-NO2-ip with 5-OH-ip leads to a compound 2 which features a doubly pillared layered structure with pcu topology. Compounds 4 and 5 are constructed from L-2 ligand with 5-NO2-ip or 5-CH3-ip, respectively. Compound 4 has non-interpenetrating (4,4) layer, while compound 5 shows unusual 2D- > 3D polycatenation of bilayers. The results reveal a new approach toward tuning structural topologies of coordination polymers through modifying the substitute groups in organic ligands. Furthermore, the photoluminescent properties of compounds 1-5 have been studied in the solid state at room temperature. (C) 2012 Elsevier Inc. All rights reserved.