Spontaneous Formation of Novel Luminescent Dinuclear Lanthanide Complexes That Emit in the Visible and Near-IR Regions

The reaction of tetrasodium-4,4′,6,6′-tetracarboxy-2,2′-bipyridine (Na₄L) with various lanthanide ions yields a family of isostructural supramolecular {Na₂[Ln₂L₂]} complexes (1−4), where Ln^III = Eu, Nd, Gd, and Tb. Strikingly, these complexes luminesce in buffered H₂O or D₂O solutions in either the visible or near-IR regions, despite their high hydration states.