Synthesis and spectral investigation of a Turn-On fluorescence sensor with high affinity to Cu2+

Three anthracene derivatives (1a, 1b and 1c) containing a Schiff base moiety were synthesized and investigated as chemosensors for the detection of Cu2+. 1a displayed extremely high selectivity to Cu2+ over other 12 interference ions with 120-fold fluorescence enhancement at 468 nm in the acetonitrile media. The nitrogen atom in Schiff base and sulfur atom of 1a provided a binding scaffold for recognition of Cu2+ with high affinity (Ka = 4.35 × 104 M−1). The formation of 1a-Cu2+ complex caused a decrease of electron density on nitrogen atom and sequentially led to fluorescence enhancement based on the photoinduced electron transfer (PET) mechanism. The design used for these three molecules afforded a new model for construction of fluorescence sensors based on PET mechanism.