Triazole based 8-formyl coumarin-glycine conjugate: A specific turn-on fluorescent probe for CuII ion

Department of Chemistry, Jadavpur University, Kolkata-700 032, India E-mail: arunabha.thakur@jadavpuruniversity.in Department of Chemical Science, Indian Institute of Science Education and Research Kolkata, Mohanpur-741 246, West Bengal, India E-mail: babuiitm07@gmail.com Manuscript received online 18 October 2018, accepted 12 November 2018 We have synthesized a new triazole based 8-formyl coumarin-glycine conjugate, (1), which displays turn-on fluorescent signal in presence of Cu2+ ion. The resulting complex displayed high selectivity towards Cu2+ ion not only via fluorescence emission but also exhibited a drastic color change from colorless to light green, which signifies the naked eye detection of Cu2+ ion. Other metal ions, e.g. Cd2+, Co2+, Fe2+, Fe3+, Hg2+, Mg2+, Mn2+, Ni2+, Pb2+ and Zn2+ produced no obvious changes in colorimetric experiment as well as in the fluorescence emission spectra. The binding constant (2.88×104 M–1) and ligand-metal binding ratio (1:1) were determined from fluorescence spectral data and Job’s plot analysis respectively. The detection limit for the present probe towards CuII ion was calculated as low as 78 nM. Furthermore, on the basis of the 1H NMR titration, HRMS and DFT study, probable binding mode of 1 with Cu2+ has been proposed