Series of Cd(II) Metal–Organic\nFrameworks Based\non a Flexible Tripodal Ligand and Polycarboxylate Acids: Syntheses,\nStructures, and Photoluminescent Properties

Abstract

Five novel metal–organic frameworks with a 1,3,5-tris­(triazol-1-ylmethyl)-2,4,6-trimethylbenzene\n(tttmb) flexible tripodal block, namely, {[Cd­(tttmb)­(atc)]·1.5H₂O}<i>_n</i> (<b>1</b>), {[Cd₅(tttmb)₂(tbi)₅(H₂O)₄]·2H₂O}<i>_n</i> (<b>2</b>), {[Cd₃(tttmb)₂(bdc)₃(H₂O)₃]·0.5H₂O}<i>_n</i> (<b>3</b>), {[Cd₂(tttmb)₂(btc)­Cl]·3H₂O}_<i>n</i> (<b>4</b>), and {[Cd₂(tttmb)₂(btec)­(H₂O)₃]·H₂O}_<i>n</i> (<b>5</b>) (H₂atc = 1,3-adamantanedicarboxylic acid, H₂tbi = 5-<i>tert</i>-butylisophthalic acid, H₂bdc = 1,4-benzenedicarboxylic\nacid, H₃btc = 1,2,4-benzenetricarboxylic acid, and H₄btec = 1,2,4,5-benzenetetracarboxylic acid), have been synthesized.\nComplex <b>1</b> exhibits a two-dimensional structure with left-\nand right-handed helical chains arranged alternately. Complex <b>2</b> displays an intricate two-dimensional framework containing\nthree layers with a 3,4,7-connected topology. It is notable that tbi^2– takes on five different coordination modes in <b>2</b>. Complex <b>3</b> presents a 3D 3,4-connected network\nwith a point symbol of (6³)₂(6⁴·8²)₂(6³·8³). The structure\nof complex <b>4</b> is a self-penetrating 3D 3,4,8-connected\nframework with left- and right-handed helical chains arranged alternately.\nComplex <b>5</b> shows a 3D pillar-layered framework, which\ncan be simplified as a 3,4,5-connected 3D topology with a Schläfli\nsymbol of (5³)­(5²·6²·7·9)­(5⁵·6²·7²·8). Moreover,\nthe investigation of photoluminescence properties reveals that complexes <b>1</b>–<b>5</b> show different fluorescent behaviors.