PH-dependent fluorescence sensing activities of two water-stable 2-D zinc(II) compounds

Abstract

Two 2-D Zn(II) compounds, namely, [Zn(HL1)(bpy)]n (1) and {[Zn(HL2)(bpe)]·0.5bpe}n (2) (H3L1=5-(2′-carboxyl phenoxy)isophtalic acid, H3L2=1,3-bis(2-carboxylphenoxy)benzoic acid, bpy=4,4′-bipyridine, bpe=4,4′-vinylenedipyridine), have been solvothermally synthesized from two flexible phenolic carboxylic acid ligands. Both compounds exhibit 2-D layered structures with 4-conneted 44 and 3- connected 63 topology, respectively. PXRD indicated that these compounds were stable in the basic conditions with pH range of 7–11 and their fluorescence intensities are strongly correlated with the pH value. The protonated carboxylic groups may have influences on the resulting fluorescence intensities. The possible proton transfer mechanism was discussed for such pH sensors in details through FTIR and ICP measurements. In addition, the analytical efficiency and accuracy in practical applications of these sensors were performed on the real lake water.