Synthesis and structural analysis of push-pull imidazole-triazole based fluorescent bifunctional chemosensor for Cu2+ and Fe2+ detection

Ana Da Lama, José Pérez Sestelo, Laura Valencia, David Esteban-Gómez, Luis
A. Sarandeses, M. Montserrat Martínez

Abstract

Dyes and Pigments 205 (2022) 110539, DOI: 10.1016/j.dyepig.2022.110539

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Fluorescent imidazole-triazole based ligands L1 and L2 have been designed as chemical push-pull chemosensors
for divalent metal ions and synthesized through palladium-catalyzed cross-coupling reactions using indium organometallics
and click chemistry. The novel ligands exhibit intense absorption in the ultraviolet region with
high molar extinction coefficients, and strong fluorescence emission with large Stokes displacements. On the
basis of UV–Vis absorption spectroscopy and fluorescence emission data in acetonitrile, L1 is shown as a
bifuncional chemosensor with differential response for Fe2+ and Cu2+ over a range of selected 3d divalent and
other metal ions. The binding site of the ligand was established by single-crystal X-ray diffraction and 1H NMR
spectroscopy studies. The association constants, determined by spectrofluorimetric titrations, show a steady
binding affinity of L1 for Cu2+ and Fe2+ in comparison with other previously reported fluorescent bidentate
chemosensors, offering the lowest limit of detection (LOD) with Cu2+. DFT calculations provide a rationale
properly understanding and interpreting the experimentally observed results. Indeed, a mechanism of the
different optical responses of L1 towards 3d divalent metal ions is proposed.