| Abstract
| - The reaction of half-sandwich complexes of ruthenium, rhodium, and iridium with amino-substituted3-hydroxy-2-pyridone ligands in aqueous solution gives monomeric O,O‘-chelate complexes. Upon additionof base, the complexes assemble to form trimeric metallamacrocycles, as evidenced by NMR spectroscopyand single-crystal X-ray analyses. The macrocycles are able to act as highly selective receptors for lithiumions. The binding constants depend on the nature of the half-sandwich complex, the ligand, and the pH.With a commercially available (cymene)Ru complex, a receptor with a Li+ binding constant of Ka = 5.8(±1.0) × 104 M-1 and a Li+−Na+ selectivity of 10 000:1 can be obtained. The fact that the assembly processof the receptor is pH-dependent can be used to detect the presence of lithium ions by a pH measurement.Furthermore, it is possible to transduce the binding of Li+ into a change of color by means of a chemicalreaction with FeCl3. This allows the detection of Li+ in the pharmacologically relevant concentration rangeof 0.5−1.5 mM by the “naked eye”.
|
