A new photoresponsive coumarin-derived Schiff base: Chemosensor selectively for Al3+ and Fe3+ and fluorescence “turn-on” under room light

A novel coumarin Schiff base compound (L) prepared from 4-(diethylamino)salicylaldehyde and 6-amino-7-hydroxycoumarin was synthesized and evaluated as a chemoselective Fe3+ and Al3+ sensor utilizing “turn-on” fluorescence enhancement. There were 7-fold and 4-fold fluorescence enhancement of L at λem,max = 488 nm upon the addition of 1 equiv. of Al3+ and Fe3+, respectively. Other metal ions, such as K+, Li+, Na+, Cu+, Mg2+, Ca2+, Ba2+, Cu2+, Fe2+, Hg2+, Ni2+, Sb3+, Sn2+, Zn2+, Ce3+, Cr3+, Pr3+, Sm3+ and Sn4+ had no such significant effect on the fluorescence of L, whereas In3+ and Ga3+ induced slightly fluorescence enhancement of L. In addition, rapid photoresponse through fluorescence “turn-on” signaling displayed L via intramolecular OH⋯NCH interaction in photoisomerized product (L′) has been described, where showed 130-fold and 65-fold fluorescence enhancement at λem,max = 488 and 516 nm, respectively. The results indicated L′ was less reactive or inert toward metal ions.