Chapter 235 Lanthanide Near-Infrared Luminescence in Molecular Probes and Devices

This chapter describes molecular, near infrared (NIR)-emitting compounds containing NdIII, ErIII, or YbIII and discrete molecular edifices containing other ions emitting in this range. It also reviews various synthetic strategies proposed for encapsulation of ions into molecular edifices and making use of macrocyclic or acyclic ligands or of d-transition metal complexes. The chapter presents novel approaches resorting to inorganic clusters, inorganic–organic hybrids, nanoparticles, or ionic liquids, and potential applications including medical imaging. The chapter illustrates the potential of organic complexes and materials for NIR-luminescent probes and highlights the difficulty in achieving reasonable emission efficiency. Some promising systems for inclusion of NIR-emitting LnIII ions are ionic liquids in which tetrakis(β-diketonates) act as the anion or doped ionogels generated by the confinement of ionic liquids within a porous silica matrix. These gels have excellent mechanical, thermal, and optical properties and feature high ionic conductivity, a key factor for electroluminescent devices.