A highly selective fluorescent chemosensor for Al³⁺ based on 2,2':6',2'-terpyridine with a salicylal schiff base

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⁺. (author)