Covalent linking of a Ru(terpy)(2)(2+) substituent improves recognition and sensing properties of the urea subunit toward anions. Urea's anion affinity is enhanced by the electrostatic attraction exerted by the Ru-II cation and by the electron-withdrawing effect exerted by the entire polypyridine-metal complex. Such an enhancement of the anion affinity, which results from the combination of a through-space and a through-bond effect, is greater than that exerted by the classical neutral electron-withdrawing substituent nitrophenyl. Small yet significant modifications of pi-pi* and MLCT bands of the Ru(terpy)(2)(2+) chromophore, detected through UV-vis spectrophotometric titrations, allowed the determination of the constants for the formation of receptor-anion H-bond complexes in diluted MeCN solution. On H-1 NAIR titration experiments, carried out under more concentrated conditions, the interaction of a second Cl- ion was observed, taking place through an outer-sphere mechanism. The Ru(terpy)(2)(2+) substituent favors the deprotonation of a urea N-H fragment on addition of a second equivalent of fluoride, with formation of HF2-.