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