A FLUORESCENT CHEMOSENSOR FOR THE COPPER(II) ION

Abstract The two-component system anthracene-9-carboxylic acid 1,4,8,11-tetrathia-cyclotetradecan-6-ylester ( 1 ) has been synthesized, structurally characterized and investigated as a fluorescent chemosensor for the Cu 11 ion. Crystallographic details for 1 : space group P 2 1 / c with α = 9.894(2), b = 24.608(2), c = 10.759(2) A , α = 90, β = 105.88, γ = 90°; V = 2519.7 A 3 , Z = 4 (R = 0.088, R w = 0.066) . In ethanolic solution 1 selectively incorporates Cu 11 into its tetrathia crown component in the presence of other 3d metal ions and signals the recognition through the quenching of the fluorescence of the anthracene fragment. Quenching of the photo-excited state (which has a charge transfer nature) takes place through a photo-induced electron transfer from the fluorophore to the metal center and involves the Cu II /Cu I couple. The d 10 cation Ag 1 competes successfully with Cu 11 for the tetrathia cavity of 1 in an ethanolic solution (not in an acetonitrile solution), but the occurrence of the metal/receptor interaction cannot be signalled, due to the poor redox activity of the non-transition cation Ag 1 .