2,2',2"-terpyridine can form complexes with various transition metal or lanthanide cations. Once these complexes are formed a strong room temperature ligand-centered green fluorescence is emitted which is attributed to excited state conformation transitions. If ion and ligand are compartmentalized no fluorescence is emitted but if the two entities are brought to close proximity, e.g. in micellar environments or by association with large poly(ethyleneoxide) chains, it is possible to observe ligand-to-metal energy transfer which leads to metal-centered luminescence, as in the case of Tb3+ or Eu3+. (C) 2003 Elsevier B.V. All rights reserved.