Solid phase synthesis of N-alkyl-bis-o-aminobenzamides for metal ion sensing based on a fluorescent dansyl platform.

In this paper, we report the synthesis on Merrifield's resin of alkyl-bis-o-aminobenzamides labeled with a fluorescent dansyl group for use in metal ion recognition. The influence of alkyl groups with different long chains (n = 1, 2, 4, 6) on the spectral fluorescence characteristics was studied. The sensing properties of the beads were evaluated by packing the resins into a flow-through cell for use in a FIA (flow injection analysis)format. Results demonstrated that for those materials with a longer alkyl chain, the fluorescence emission increased upon Li+, Na+, K+, Ca2+, and Mg2+ addition with a higher sensitivity for Mg2+. On the contrary,a fluorescence quenching was observed when Cu2+, Fe3+, or Zn2+ ions were added. The potential applicability of the sensing approach described in this paper for magnesium ions and the sensing response mechanism are outlined.