Dinuclear lanthanide (Ln=Tb 3+ or Eu 3+) complexes (Ln 2 L2) of two octadentate macrocyclic polyaminopolycarboxylic ligands connected through a benzophenone (BP) moiety ( L2) have been synthesized. Sensitized luminescence properties of Ln 2 L2 in water have been studied in comparison to those of BP-conjugated mononuclear Ln complexes (Ln L1). The luminescence intensity of Tb 2 L2 is lower than that of Tb L1 because of lower triplet quantum yield of the BP moiety. In contrast, Eu 2 L2 shows higher intensity than Eu L1. For both Eu complexes, energy level of triplet excited-state BP ( 3BP*) is only 3 kJ mol −1 higher than that of 5D 2 excited-state of Eu 3+. The 5D 2 state formed by a triplet-energy transfer (TET) from 3BP* is therefore deactivated by a back energy transfer (BET) to the ground-state BP, resulting in low luminescence intensity of Eu L1. In contrast, within Eu 2 L2, TET from 3BP* to 5D 0 state of two Eu 3+ ions is accelerated, thus leading to higher luminescence intensity. Another notable feature of Eu 2 L2 is the luminescence quantum yield independent of its concentration. In contrast, for Eu L1 system, an intermolecular BET occurs from 5D 2 state of Eu 3+ to the ground-state BP conjugated to another Eu L1 complex, resulting in a yield decrease with the concentration increase.