Pyrene appended bis-triazolylated 1,4-dihydropyridine as a selective fluorogenic sensor for Cu2+

Abstract A Pyrene appended bis -triazolylated-1,4-dihydropyridine based fluorescent probe L1 was synthesized using Cu(I)-catalyzed click chemistry approach. Among the various metal ions tested, L1 showed selective binding towards Cu 2+ . L1 formed a 1:1 ligand-metal complex with an association constant, K a  = 6.63 × 10 4  M −1 as revealed by Job's plot and Benesi-Hildebrand plot, respectively. The detection limit of L1 for Cu 2+ was found out to be 0.53 μM. The fluorescence response of L1 and L1 -Cu 2+ with varying pH was determined which showed that L1 works well, over a broad pH range. The binding mechanism of L1 with Cu 2+ was well explored by density functional theory studies. Further, the probe was found to be non toxic under experimental conditions in various cancerous and normal cell lines. Fluorescence microscopy showed that L1 was cell permeable and could be served as a fluorescent probe for the detection of the presence and absence of Cu 2+ analytes in human primary glioblastoma cells (U-87). Also, paper strips of L1 were tested in aqueous media to set up a cost effective method for detection of Cu 2+ ions.