Schiff base fluorescence probes for Cu2+ based on imidazole and benzimidazole

•Two new Schiff base fluorescence probes were designed and synthesized.•Theoretical calculations showed the compounds could coordinate with metal ions.•Experiments showed that the compounds have outstanding fluorescence properties.•The fluorescence probes exhibited excellent sensitivity and selectivity for Cu2+.

Two novel Schiff base fluorescence probes for Cu2+ were designed and synthesized by reactions between p-fluorobenzaldehyde, p-phenylenediamine and heterocyclic compound (including imidazole and benzimidazole). The optimized geometries, frontier orbitals, molecular orbital contributions and excitation energies for the probes were predicted at B3LYP/6-31G* by theoretical calculation. And the probes were characterized by FTIR, 1H NMR, UV–vis and fluorescence spectroscopy. Test results showed the probes had a high selectivity for Cu2+ compared to other metal ions measured (Ag+, Co2+, Mg2+, Ni2+, Pb2+, Zn2+, Cd2+ and Fe3+). From test results, a high selectivity for Cu2+ was discovered in this type of probes, especially, the probe based on benzimidazole exhibited more significant enhancement in fluorescence intensity compared with imidazole-based due to its relative large conjugate rigid plane structure. The detection mechanism of the synthesized probes with high selectivity for Cu2+ was also discussed.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slide