Preparation of a metal–ligand fluorescent chemosensor and enantioselective recognition of carboxylate anions in aqueous solution

Two chiral fluorescent chemosensors 1 and 2 were synthesized, and the structure characterized by IR, 1H NMR, 13C NMR, MS spectra and elemental analysis. Their recognition ability was studied in aqueous solution (Tris–HCl buffer pH 7.4, MeOH/H2O = 1:1) through fluorescence spectra. Receptors 1 and 2 showed a good binding ability to the copper ion. The host 1-Cu2+ complex showed a chiral recognition ability to mandelate anions with a preferable binding to l-mandelate than d-mandelate anions. The host 1-Cu2+ complex and l- or d-mandelate anions formed 1:1 stoichiometric complex. The binding constant for l-mandelate is 576 M−1, whereas that for d-mandelate is only 38 M−1, which can be distinguished by the different change of fluorescence intensity.

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tert-butyl (S)-1,3-bis(2-((anthracen-10-yl)methylamino)ethylcarbamoyl)propylcarbamateC44H49N5O4[α]D20=-169 (c 0.071, CHCl3)

tert-butyl (S)-1,3-bis(3-((anthracen-10-yl)methylamino) propylcarbamoyl)propylcarbamateC46H53N5O4[α]D20=+81.1 (c 0.074, CHCl3)

(S)-N1, N6-bis(2-((anthracen-10-yl)methylamino)ethyl)2-aminopentanediamideC39H41N5O2[α]D20=-114.2 (c 0.061, CHCl3)

(S)-N1, N6-bis(3-((anthracen-10-yl)methylamino)propyl)-2-aminopentanediamideC41H45N5O2[α]D20=+109 (c 0.064, CHCl3)