pH-triggered assembly of organometallic receptors for lithium ions.
The reaction of half-sandwich complexes of ruthenium, rhodium, and iridium with amino-substituted 3-hydroxy-2-pyridone ligands in aqueous solution gives monomeric O,O'-chelate complexes. Upon addition of base, the complexes assemble to form trimeric metallamacrocycles, as evidenced by NMR spectroscopy and single-crystal X-ray analyses. The macrocycles are able to act as highly selective receptors for lithium ions. 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 K(a) = 5.8 (+/-1.0) x 10(4) M(-1) and a Li+-Na+ selectivity of 10 000:1 can be obtained. The fact that the assembly process of 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 chemical reaction with FeCl(3). This allows the detection of Li+ in the pharmacologically relevant concentration range of 0.5-1.5 mM by the "naked eye".
Grote
Zacharias
Z
Institute of Chemical Sciences and Engineering, Swiss Federal Institute of Technology Lausanne (EPFL), 1015 Lausanne, Switzerland.
Scopelliti
Rosario
R
Severin
Kay
K
D002414:Cations, Monovalent; D003124:Colorimetry; D018360:Crystallography, X-Ray; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008094:Lithium / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D009942:Organometallic Compounds / Q000737:chemistry*; D011728:Pyridones / Q000737:chemistry; D011955:Receptors, Drug / Q000737:chemistry; D012428:Ruthenium / Q000737:chemistry
D002414:Cations, Monovalent; D009942:Organometallic Compounds; D011728:Pyridones; D011955:Receptors, Drug; D012428:Ruthenium; D008094:Lithium