Synthesis, characterization, Density Functional Theory (DFT) calculation, and fluorescent study of an efficient and novel Schiff base Cu(II) sensor

A Schiff base fluorescent “turn-off” sensor L based on 2, 4-diamino-6-hydroxypyrimidine, and 2-hydroxy-1-naphthaldehyde was synthesized, which shows excellent selectivity and sensitivity towards Cu²⁺ ions in an aqueous medium. The detection limit of the probe was found to be 11.92 µM which is much lower than the acceptable level of Cu²⁺ ions in drinking water as set by the World Health Organization (30 µM) and the U. S. Environmental Protection Agency (20 µM). Furthermore, a 1: 0.5 binding stoichiometry between the probe and Cu²⁺ ion was confirmed from the fluorescence titration data, Job’s plot, and DFT calculation. The binding constant (K_a) of Cu²⁺ ion with the probe was found to be 6.3 × 10⁴ M⁻¹. Thus, the overall study reveals that the synthesized Schiff base ligand is a potential fluorescent sensor for Cu²⁺ions.

Graphical abstract

The research study includes the synthesis of a novel and efficient Schiff base ligand L, which is highly sensitive and a selective fluorescent sensor for Cu²⁺ ions with a very low detection limit.