Synthesis and Properties of Sodium and Europium(III) Cryptates Incorporating the 2,2′‐Bipyridine 1,1′‐Dioxide and 3,3′‐Biisoquinoline 2,2′‐Dioxide Units

The sodium and europium cryptates of the new macrobicyclic ligands 2 and 3 incorporating the 2,2′‐bipyri dine 1,1′‐dioxide and 3,3′‐biisoquinoline 2,2′‐dioxide units, respectively, have been prepared. The Eu III complexes present characteristic 1 H‐NMR spectra, showing large shifts, and are strongly luminescent in aqueous solution. These markedly improved luminescent properties, compared to the europium cryptate of the parent macrobicyclic ligand 1 , may be ascribed at least in part to a better shielding of the bound cation by the N ‐oxide sites.