The Role of Ligand Topology in the Decomplexation of Luminescent Lanthanide Complexes by Dipicolinic Acid

In this study, we present the aqueous solution behavior of twoluminescent lanthanide antenna complexes (Eu3+1,Dy3+9)with different ligand topologies in the presence of dipicolinicacid (DPA, pyridine- 2,6-dicarboxylic acid). Macrocyclic (1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid, DO3A, 9) and acyclic(1,4,7-triazaheptane-1,1,7,7-tetraacetic acid, DTTA, 1 ) ligandshave been selected to form a ratiometric pair in which Dy3+9acts as a reference and Eu3+1 acts as a probe for the recog-nition of DPA. The pair of luminescent complexes in water re-veals the capability to work as a DPA luminescent sensor. Thechange of emission intensity of Eu3+indicates the occurr enceof a new sensitization path for the lanthanide cation throughexcitation of DPA. NMR evidence implies the presence of free1 and mass spectrometry shows the formation of emitting[EuDPA2]as a result of a ligand exchange reaction.