A highly selective fluorescent chemosensor for silver(I) in water/ethanol mixture

Synthesis, photophysical, and complexation properties of fluorescent chemosensors, L1 and L2, with ‘receptor-spacer-fluorophore’ motif (L1: NS2O2-cyclic receptor, L2: acyclic analogue receptor) are described. Maximum chelation-enhanced fluorescence effect (TURN-ON type) was observed in the presence of Ag+ for both fluoroionophores in a 1:1 (v/v) aqueous ethanol solution: remarkably superior selectivity of L1 (150-fold) with cyclic receptor than that of the L2 (50-fold) with acyclic analogue was found. According to the fluorescence and NMR titrations, the excellent selectivity of L1 is attributed to its topology-based higher affinity in complexation.