Colorimetric detection of achiral anions and chiral carboxylates by a chiral thiourea-phthalimide dyad.

The chiral chemosensor 1, based on a thiourea-activated phthalimide, is available by four reaction steps from 4-nitrophthalimide. 1 detects fluoride, chloride, acetate, and dihydrogen phosphate anions by changes in UV-vis absorption. Fluoride in excess induces deprotonation whereas the other anions show only complex formation in the ground state. (1)H-NMR studies confirm the formation of these H-bonded complexes and the fluoride-induced receptor deprotonation in the recognition process. Moderate chiral recognition was observed for sodium D/L-lactate with K(ass)(D)/K(ass)(L) = 1.93.