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 (Na<sub>4</sub>L) with various lanthanide ions yields a family of isostructural supramolecular {Na<sub>2</sub>[Ln<sub>2</sub>L<sub>2</sub>]} complexes (<b>1</b>−<b>4</b>), where Ln<sup>III</sup> = Eu, Nd, Gd, and Tb. Strikingly, these complexes luminesce in buffered H<sub>2</sub>O or D<sub>2</sub>O solutions in either the visible or near-IR regions, despite their high hydration states.