Carboxylate ligands-directed synthesis of cucurbit[5]uril-based coordination polymers for the detection of norfloxacin

Abstract

Owing to the large-scale abuse of antibiotics and their great threat to human health, developing efficient sensing materials to monitor antibiotics have attracted enormous attention in recent years. In this work, three novel cucurbit[5]uril-based (Q[5]) coordination polymers (CPs) with the formula of [Ba2(NO3)(H2O)3(L1)(Q[5])]‧8H2O (1), [Ca(H2O)3(L2)(Q[5])0.5] (2) and [Ba4(H2O)4(L3)(Q[5])2]‧(NO3)4‧30H2O (3) were synthesized by employing three different aromatic carboxylate ligands [1,1'-biphenyl]-3,4',5-tricarboxylic acid (H3L1), 2,2'-dinitro-[1,1'-biphenyl]-4,4'-dicarboxylic acid (H2L2), and [1,1'-biphenyl]-3,3',5,5'-tetracarboxylic acid) (H4L3) as the second ligand. Crystal structural analysis revealed that complex 1, 2 and 3 displayed an interesting structural variation from 1D coordination chains (1) to 2D coordination networks (2) to unique 3D coordination frameworks (3), suggesting that the substitution groupsand the coordination modes of the introduced second ligands have significant effect on the structural dimensions of the formed Q[5]-based coordination polymers. More impressively, complex 2 showed a unique fluorescence ratiometric sensing capability toward norfloxacin (NFX) in aqueous media with high selectivity, superior sensitivity and low detection limit.