Colorimetric detection of fluoride ion by 5-arylidenebarbituric acids: dual interaction mode for fluoride ion with single receptor.
Two 5-arylidenebarbituric acid derivatives (IH and IM) have been synthesized by the Knoevenagel condensation of barbituric acid with 4-N,N-dimethylamino benzaldehyde and studied for anion sensing activities. Both receptors sense fluoride ion with high selectivity and sensitivity and the sensing action has been demonstrated by naked eye detection, UV-visible absorption, and fluorescence spectral changes in the presence of F(-). Indeed, the F(-) sensing mechanism for receptor IH depends on F(-) ion concentration. While at higher concentrations F(-) forms strong hydrogen bonding interaction with the N-H proton of the receptor, at lower concentrations sensing is influenced by the deprotonation of the methylene proton, followed by the chemical reaction, which is also confirmed by the (1)H-NMR technique. On the other hand, when replacing the N-H proton with a methyl group, IM does not show any concentration dependent behaviour with F(-). The F(-) concentration dependent sensing is attributed to the changes in the receptor-anion interaction equilibrium, where at higher F(-) concentrations, F(-) interacts with the receptor through hydrogen bonding and at lower concentrations it induces a chemical reaction.
Center for Condensed Matter Sciences, National Taiwan University, Taipei, 106, Taiwan, Republic of China. leewang@ntu.edu.tw.
Chinnusamy
C
Saravanan
Shanmugam
S
Easwaramoorthi
Leeyih
L
Wang
D001463:Barbiturates / Q000138:chemical synthesis / Q000737:chemistry*; D003124:Colorimetry; D005459:Fluorides / Q000032:analysis* / Q000737:chemistry
D001463:Barbiturates; D005459:Fluorides