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)]·1.5H2O}n (1), {[Cd5(tttmb)2(tbi)5(H2O)4]·2H2O}n (2), {[Cd3(tttmb)2(bdc)3(H2O)3]·0.5H2O}n (3), {[Cd2(tttmb)2(btc)­Cl]·3H2O}n (4), and {[Cd2(tttmb)2(btec)­(H2O)3]·H2O}n (5) (H2atc = 1,3-adamantanedicarboxylic acid, H2tbi = 5-tert-butylisophthalic acid, H2bdc = 1,4-benzenedicarboxylic acid, H3btc = 1,2,4-benzenetricarboxylic acid, and H4btec = 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 tbi2– takes on five different coordination modes in 2. Complex 3 presents a 3D 3,4-connected network with a point symbol of (63)2(64·82)2(63·83). 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 Schläfli symbol of (53)­(52·62·7·9)­(55·62·72·8). Moreover, the investigation of photoluminescence properties reveals that complexes 1–5 show different fluorescent behaviors.