Syntheses, Structures And Properties Of Metal-Organic Frameworks Based On A Thiacaliaxarene Ligand

By using a novel thiacalix[4]arene ligand 25,26,27,28-tetrakis[?1-propyl-1H-imidazole?]-5,11,17,23-tetra-tert-butyl-2,8,14,20-thiacalix[4]arene?TIT4A?and five kinds of dicarboxylic acids,five Cd?II?-based compounds,[Cd₂?TIT4A??L1?₂]·DMF?1?,[Cd₂?TIT4A??L2?₂]?2?,[Cd₂?TIT4A??L3?₂]?3?,[Cd₂?TIT4A??L4?₂]·MeOH·DMF?4?and[Cd?TIT4A?_0.5?L5?]·EtOH?5??H₂L1=isophthalic acid,H₂L2=4,4'-stilbene-dicarboxylic acid,H₂L3=azobenzene-4,4'-dicarboxylic acid,H₂L4=4,4'-biphenyl-dicarboxylic and H₂L5=4-[4-?4-carboxyphenyl?phenyl]benzoic acid?have been constructed.Their structures were determined by single crystal X-ray diffraction.In compound 1,Cd?II?is coordinated with TIT4A ligands to form a layered structure,and L1^2-anion further connects these layered structures to form a three-dimensional network structure.Compounds 2 and 3 are isomorphic and have the same connection mode as compound 1,however,the three-dimensional network structure is different from compound 1 because of the difference between the nitrogen atoms on the imidazole and the Cd?II?connection angle.Specially,4 and 5 display 2-fold and 3-fold interpenetrating three-dimensional frameworks because of the diverse spacer length of dicarboxylic acids.By fluorescence detection of metal cations,anions and organic small molecules,1-5 show fluorescence quenching to Cr₂O₇^2-,MnO₄^-,Fe³⁺and nitrobenzene.1,4and 5 display apparent fluorescence enchantment effect to CO₃^2-or Al³⁺.