Amino acid recognition by fine tuning the association constants: tailored naphthalimides in pillar[5]arene-based indicator displacement assays

Three aminonaphthalimide derivatives were synthesized bearing different anchoring groups in their 4-position in order to adjust the supramolecular interactions with carboxylato-pillar[5]arene (WP5), an anionic, water-soluble host. The modification of the anchor groups resulted in varying association constants embracing three orders of magnitude (K-a from similar to 10(3) to similar to 10(6)) in buffered water. Since the fluorophore responded significantly to the electronic environment, large fluorescence quenching was observed with the anionic WP5 host. The naphthalimide indicator-WP5 supramolecular assemblies were used to detect arginine and lysine with complete selectivity over other non-basic alpha-amino acids by turnon fluorescence. The same assemblies proved to be highly sensitive fluorescence displacement assays for the detection of cadaverine.