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.

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