Series of Cd(II) Metal-Organic Frameworks Based on a Flexible Tripodal Ligand and Polycarboxylate Acids: Syntheses, Structures, and Photoluminescent Properties

Five novel metal organic frameworks with a 1,3,5-tris-(triazol-1-ylmethyl)-2,4,6-trimethylbenzene (tttmb) flexible tripodal block, namely, {[Cd(tttmb)(atc)]center dot 1.5 H2O}(n) (1), {[Cd-5(tttmb)(2)(tbi)(5)(H2O)(4)]center dot 2H(2)O)(n), (2), {[cd(3)(tumb)(2)(bdc)(3)(H2O)(3)]center dot 0.5H(2)O}(n), (3), {[Cd-2(tttmb)(2)(btc)-Cl]3H(2)O} (4), and {[Cd-2(tttmb)(2)(btec)(H2O)(3)]center dot H2O}(n) (5) (H(2)atc = 1,3-adamantanedicarboxylic acid, H(2)tbi = 5-tert-butylisophthalic acid, H(2)bdc = 1,4-benzenedicarboxylic acid, H(3)btc = 1,2,4-benzenetricarboxylic acid, and H(4)btec = 1,2,4,5-benzenetetracarboxylic acid), have been synthesized. Complex 1 exhibits a two-dimensional structure with left- and right-handed helical chains arranged alternately. Complex 2 displays an intricate two-dimensional framework containing three layers with a 3,4,7-connected topology. It is notable that tbi(2-) takes on five different coordination modes in 2. Complex 3 presents a 3D 3,4-connected network with a point symbol of (6(3))(2)(6(4).8(2))(2)(6(3).8(3)). The structure of complex 4 is a self-penetrating 3D 3,4,8-connected framework with left- and right-handed helical chains arranged alternately. Complex 5 shows a 3D pillar-layered framework, which can be simplified as a 3,4,5-connected 3D topology with a Schlafli symbol of (5(3))(5(2).6(2).7.9)(5(5).6(2).7(2).8). Moreover, the investigation of photoluminescence properties reveals that complexes 1-5 show different fluorescent behaviors.