N-Amino-thieno[3,2-c]pyridin-4-ones: a new class of aggregation induced emissive Pd2+ chemosensors

Abstract

N-Amino-thieno[3,2-c]pyridin-4-one derivatives 5a–c were synthesized in three steps using ketene dithioacetal as the primary precursor. Treatment of 3-amino-4-oxo-6-aryl-4H-thieno[3,2-c]pyran-2-carboxylate with hydrazine hydrate resulted in 3,5-diaminothieno[3,2-c]pyridine-4-one derivatives (5). The photophysical properties of different functionalized N-amino-thieno[3,2-c]pyridin-4-ones 5a–c were studied and were explored for metal sensing, which resulted in selective recognition of the Pd²⁺ metal ion over other metal ions with fluorescence turn-off properties. The fluorescence changes were observed with the “naked eye” under a 365 nm UV lamp after the addition of Pd²⁺ to the sample solution. Compounds 5b and 5c exhibit aggregation-induced emission (AIE).