Trinuclear metallamacrocycles can be obtained by reactions of (arene)Ru, CpRh and CpIr complexes with pyridonate ligands. Using 3-oxy-pyridonate as the bridging ligand, organometallic analogues of 12-crown-3 are formed, which display an extremely high affinity and selectivity for lithium and sodium ions. In the presence of guest molecules, the redox-potential of the metallamacrocyclic hosts is shifted by more than 300 mV towards positive potential suggesting potential applications as chemosensors. The affinity of the metallacrown complexes is sufficient to allow the stabilization of molecular LiFHF and LiF. The fact that complexes of LiF can be isolated was used to construct a specific receptor for fluoride ions. (C) 2003 Elsevier B.V. All rights reserved.