Fluorescent nitric oxide detection by copper complexes bearing anthracenyl and dansyl fluorophore ligands

Abstract

Anthrancenyl and dansyl fluorophore ligands [AnCH(2)pipCS(2)K (1), Ds-Hen (2), Ds-HAMP (3), Ds-HAQ (4), and Ds-HAPP (5)] were prepared for coordination to Cu-II. Five Cu complexes, [Cu(AnCH(2)pipCS(2))(2)] (6), [Cu(Ds-en)(2)] (7), [Cu(Ds-AMP)(2)] (8), [Cu(Ds-AQ)(2)] (9), and [Cu(Ds-APP)(OTf)] (10), were synthesized as candidates for detecting nitric oxide (NO) by fluorescence and characterized by X-ray crystallography. A decrease in fluorescence compared to that of the free ligands (1-5) was measured following the formation of the corresponding five Cu-II complexes 6-10. Fluorescence was restored in the presence of NO in CH3OH/CH2Cl2 solutions of the compounds. Complexes 7, 8, and 10 exhibited a fluorescence response to NO in pH 7.0 or 9.0 buffered aqueous solutions. Spectroscopic studies revealed that NO-induced fluorescence enhancement in these Cu-II complexes occurs by reduction to Cu-I. The present studies demonstrate that Cu-II complexes are effective as fluorescent probes for detecting NO in both organic and aqueous environments.