Glycerol‐Triazole Conjugated Rhodamine as Colorimetric and Fluorimetric Sensor for Cu2+.

A glycerol‐triazole tethered rhodamine based colorimetric and fluorimetric sensor 3′,6′‐bis(diethylamino)‐2‐(((1‐(1,3‐dihydroxypropan‐2‐yl)‐1H‐1,2,3‐triazol‐4‐yl)methylene)aminospiro [isoindoline‐1,9′‐xanthen]‐3‐one (L1) is designed and synthesized for the selective recognition of Cu2+ ion. The sensor L1 allows naked eye detection of Cu2+ ion with a fast response (<1 min). Among the various metal ions tested, the sensor L1 shows selective binding with Cu2+ through turn‐on fluorescence mechanism. The sensor shows 1 : 2 binding stoichiometry with binding constant, Ka=1.1×106 M−2 as revealed by job's plot & Benesi‐Hildebrand plot (B−H plot), respectively. The detection limit of L1 with Cu2+ ion is found to be 3.3 μM. Further, the experimental results are also validated using density functional theoretical (DFT) study. The optimized geometries indicates that the formation of the L1‐Cu2+ complex is thermodynamically favourable by ΔG=−11.7 kcal/mol. The HOMO‐LUMO gap of the ligand L1 is found to be 3.49 eV, which decreases to 1.76 eV upon complexation with copper. [ABSTRACT FROM AUTHOR]