Abstract

We report in this paper an unusual beta-cyclodextrin mediated-aluminum (III) ion sensing based on augmented quenching of fluorescence. The fluorescent sensing of metal ions by a new ligand prepared (L = 4-[{4-(1H-imidazol-1-yl)phenyl]imino}methyl]piperazine-1-carboxaldehyde) has been investigated as well as the effect of the supramolecular complex formation with beta-CD. In aqueous solution, L shows an increase of fluorescence due to the interaction with beta-cyclodextrin with a formation constant of 77 (+/- 12) M-1. The ROESY NMR spectrum clearly indicates that L is encapsulated by beta-CD. Theoretical calculations show the possible structure both of the L-beta-CD adduct and of the coordination mode of Al3+ ion to L. In the presence of beta-CD, the piperazine adopts a distorted conformation. It leads to an enhanced Al3+ sensing by the compound in its supramolecular complexed form. The lower limit of detection of Al3+ ions is 6.00 x 10(-8) mol L-1. This detection limit slightly expands for L in the presence of beta-CD.