Synthesis and physicochemical characterization of Schiff bases used as optical sensor for metals detection in water

•Mechanochemical synthesis of new imine and physicochemical characterization.•Imine assessment as optical chemical sensor for Cu2+ detection in aqueous medium.•Imine as Cu2+ chemical sensor with detection limit of 4.9 × 10−6 M.•Determination of the coordination complex L+ Cu2+ by IR, NMR and DFT.•Relationship between selectivity and HOMO-LUMO energy orbitals. In this work, chemical mechanic synthesis of six imines is reported, chemical structure and optical characterization is described. The imines 3a-3f were evaluated as colorimetric chemical sensors of metals: Ba2+, Co2+, Fe2+, Mg2+, Ni2+, Pb2+, Zn2+, Cd2+, Hg2+, Cu2+, Sn2+ and Cs+ where 3e being a highly selective colorimetric chemical sensor for Cu2+. The limit detection of the sensor was determined through the titration, which turned out to be 4.9 × 10−6 M with a Ka of 8.264 × 103 M−1. Also, the interference of detection in a mixture of metals was studied. Finally, by the use of IR, NMR, and DFT calculations, the structure of the 3e + M complex formed, and the phenomenon responsible for the color change was determined. Finally, a possible relationship between the selectivity to metal ions and the HOMO energy levels of the molecules is proposed, being a basis for the design of smart organic sensors [Display omitted]