Strategies for the design of luminescent lanthanide complexes, especially Nd(III) complexes are introduced in this review. The relatively low efficiency of Nd(III) emission in solution has been attributed to: (1) the radiationless transition process via vibrational excitation of the surrounding medium; (2) dipole–dipole non-radiative energy transfer processes via cross-relaxation and excitation migration; and (3) characteristics of perturbation of Nd(III) f orbitals by the surrounding environment. A Nd(III)-doped organic medium could be used as a strong luminescent material if these contributions could be controlled via the design of ligands for the Nd(III) complexes. Furthermore, recent photonic applications using Nd(III), Eu(III) and Tb(III) complexes are demonstrated in this paper. The design of lanthanide(III) complexes and luminescence-based applications, including the fabrication of devices, are expected to open up pioneering fields in materials science.

Strategies for the design of luminescent lanthanide(III) complexes and their photonic applications

Strategies for enhancing photoluminescence of Nd3+ in liquid media

The deuterated tris(hexafluoroacetylacetonato)neodymium(III) complex, Nd(HFA-D)3, was obtained by keto−enol tautomerism reaction of Nd(HFA)3 in methanol-d4 The emission of Nd(HFA-D)3 was observed in the following anhydrous deuterated organic solvents:  methanol-d4, acetone-d6, THF-d8, DMF-d7, and DMSO-d6 The intensity and lifetime of the emission in DMSO-d6 are much superior to those in other deuterated solvents The specific interaction of DMSO molecules with Nd(HFA)3 was confirmed by 13C NMR and 19F NMR analysis The strong coordination ability of DMSO to Nd3+ ion in Nd(HFA-D)3 led to the enhanced emission in DMSO owing to the suppression of radiationless transition via vibrational excitation of D2O molecules in the vicinity of Nd(HFA-D)3

Enhanced Emission of Deuterated Tris(hexafluoroacetylacetonato)neodymium(III) Complex in Solution by Suppression of Radiationless Transition via Vibrational Excitation

Publisher Summary This chapter describes molecular, near infrared (NIR)-emitting compounds containing Nd III , Er III , or Yb III 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 Ln III 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.

Charles Brecher

Papers

Comparison of aprotic solvents for neodymium(III) ion liquid laser systems: selenium oxychloride and phosphorus oxychloride