A Highly Selective Fluorescent Chemosensor for Al3+ Based on 2,2’:6’,2”-Terpyridine with a Salicylal Schiff Base

Abstract

Two 2,2’:6’,2”-terpyridine-based Schiff bases (TPySSB and TPySB) have been synthesized. The TPySSB shows remarkable selective ‘off-on’ fluorescence for Al3+ in combination with photoinduced electron transfer (PET) mechanism and C=N isomerization mechanism. Chemosensor TPySSB binds Al3+ in a 1:2 ratio with an association constant 6.8 × 105 (correlation coefficient (R2) = 0.98) and this 1:2 stoichiometric model is established on Job’s plot and 1H nuclear magnetic resonance (NMR). Comparing TPySSB and TPySB, it is of great importance the existence of oxygen atom of hydroxyl group in salicylidene due to its strong binding abilities of both phenol and C=N structure to the Al3+