Luminescent lanthanide reporters: Characterization of polymetallic dendrimer complexes

CHED 1212

Savannah J. Johnson, savannahjohnson@gmail.com1, Grzegorz Filipcyzk2, and Stéphane Petoud, spetoud@pitt.edu2. (1) Department of Chemistry, Piedmont College, 165 Central Avenue, Demorest, GA 30535, (2) Department of Chemistry, University of Pittsburgh, Chevron Science Center, Pittsburgh, PA 15260
In recent years, lanthanide complexes have gained more attention in the scientific world due to their unique photophysical properties including photostability, sharp emission bands, and long luminescent lifetimes. These characteristics make lanthanides excellent reporters in biological and medical applications, but the insufficient luminescence intensity of the current lanthanide compounds strongly limits their sensitivity in applications. In an effort to improve luminescence efficiency, lanthanide complexes formed with ligands such as dendrimers have been developed and studied in our group. One of the main advantages of this strategy is that a discrete dendrimer ligand has the ability to encapsulate several lanthanide cations and to incorporate a large number of sensitizer groups at its periphery to increase their absorbance. This results in more brilliant polymetallic lanthanide complexes. By making such improvements, these complexes have better ability to fulfill requirements for biomedical applications such as in vivo oxygen sensing. Our investigation includes synthesizing of the dendrimer-lanthanide complexes and characterizing the species formed in solution through spectrophotometric titrations. Photophysical properties have been characterized through different types of experiments including quantum yields measurements, determination of the energy position of the dendrimer singlet and triplet state and of the luminescence lifetimes. The resulting data will help us to rationalize the dendrimer to lanthanides energy transfer and to evaluate their potential for communicating vital information in bioassays.