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

Abstract

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)]·1.5H 2 O} n ( 1 ), {[Cd 5 (tttmb) 2 (tbi) 5 (H 2 O) 4 ]·2H 2 O} n ( 2 ), {[Cd 3 (tttmb) 2 (bdc) 3 (H 2 O) 3 ]·0.5H 2 O} n ( 3 ), {[Cd 2 (tttmb) 2 (btc)Cl]·3H 2 O} n ( 4 ), and {[Cd 2 (tttmb) 2 (btec)(H 2 O) 3 ]·H 2 O} 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 Schläfli 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.