Herein, we describe a new rotaxane-based molecular recognition system incorporating 2,2´-bipyridinium ions and crown ether-like macrocycles. The 1H NMR spectra of the corresponding “neutral” [2]rotaxane recorded in the presence of a mixture of the physiologically important Li+, Na+, Mg2+, and Ca2+ ions feature distinct signals for each of the complexes, with the chemical shifts of pertinent probe protons identifying the chemical nature of each metal ion. That is to say, the identification of these metal ions in solution is possible from the analysis of a single 1H NMR spectrum of a single molecular sensor.