Molecular Recognition of Strong Acids by Using a 2‐Ureido‐4‐Ferrocenyl Pyrimidine Receptor

The properties of a ferrocenyl ureidopyrimidine derivative, a potential electrochemical sensor for trifluoromethanesulfonic acid and trifluoroacetic acid, were investigated using UV/Vis, NMR, and CV measurements. Upon protonation, a structural change was found to take place leading to the formation of a proper binding site for the anion of the acid. Anion binding has been proved for both CF 3 SO 3 – and CF 3 CO 2 – as well as for the BF 4 – anion by 1 H NMR measurements. Moreover, titration experiments carried out with CF 3 SO 3 H and CF 3 CO 2 H resulted in different responses in the NMR spectra of the pyrimidine host. Cyclic voltammetry was found to be suitable to follow the addition of the acids to the host molecule. DFT calculations and X‐ray diffraction were used to explore the properties of anion binding.