Recognition of Li⁺ by a Salophen−UO₂ Homodimeric Complex

Self-assembly via mutual U-coordination of the salophen−UO2 complex 1 creates a dimeric species which is shown to be useful for metal binding. Indeed, the 1 dimer has affinity for alkali metal cations and, interestingly, a marked selectivity for Li+, determined by electrospray ionization mass spectrometry and 1H NMR techniques. X-ray diffraction helped in the elucidation of the dimeric complex structure, which presents a crown-ether-type coordination site, in analogy to the more familiar 12-crown-4, responsible for the metal interaction. Comparison with isomer 2, and the salen derivative 3, increases the understanding of the behavior of such systems in solution and in the solid state.