Colorimetric and fluorescence “turn-on” recognition of fluoride by a maleonitrile-based uranyl salen-complex

- Two new uranyl-salen complexes based on a 1,2-diaminomaleonitrile are described.
- Spectroscopic studies proof their potential use for fluoride detection.
- The presence of two bulky substituents favors the molecular recognition process.
- DFT calculations support the experimental data.

The synthesis and characterization of two new uranyl-salen complexes, 1-2, based on a 1,2-diaminomaleonitrile unit, is described. Spectroscopic studies to evaluate their potential as colorimetric probes for fluoride detection in chloroform and dichloromethane were undertaken. Compound 2 exhibits a 'turn-on' response characterized by a naked-eye colorimetric change for the selective recognition of fluoride in both solvents. DFT calculations show that the stabilization energy for the formation of the host:guest complex follows the trend F− > Cl− > Br− hence supporting the experimental data.