Alkynyl Ruthenium Colorimetric Sensors: Optimizing the Selectivity toward Fluoride Anion

We report on the synthesis of alkynyl ruthenium colorimetric sensors whose receptors are constituted by
thiazolidinedione, rhodanine, or barbituric heads as recognition centers for anions. As modifications in the charge
density at these recognition centers affect the whole molecule, through the alkynyl ligand acting as a communicating
wire, the effects of hydrogen-bonding interactions with the anions were observed with the naked eye and monitored
by UV−vis absorption spectrometry. The selectivity of the sensors was improved through electronic modifications
of the alkynyl ruthenium subunit:  the higher the electron density at the receptor head, the higher the selectivity is.
TD-DFT calculations rationalize the long-range electronic communication as a main characteristic of the alkynyl
ruthenium species and as a key to improve the selectivity of alkynyl ruthenium-based sensors toward anions.