A coumarin-based turn-on fluorescent sensor for the determination of Al3+: single crystal X-ray structure and cell staining properties

An efficient Al3+ receptor, 6-(2-hydroxybenzylideneamino)-2H-chromen-2-one (HBC), has been synthesized by condensing salicylaldehyde with 6- aminocoumarin. The molecular structure of HBC has been determined by a single crystal X-ray analysis. It was established that in the presence of Al3+, HBC shows 25 fold enhancement of fluorescence intensity which might be attributed to the chelationenhanced fluorescence (CHEF) process. HBC binds Al(NO3) 3 in a 1 : 1 stoichiometry with a binding constant (K) of 7.9 x 104 M-1. Fe3+ and Mn2+ quench the emission intensity of the [HBC + Al3+] system to an insignificant extent at a concentration 10 times higher compared to that of Al3+. HBC is highly efficient in the detection of intracellular Al3+ under a fluorescence microscope.