Microwave Synthesis and Luminescence Efficiencies in Mixed-Ligand Europium Complexes.

The microwave-assisted methodology is now extended and fine-tuned for the synthesis of mixed-ligand europium complexes with an average reaction time of 12 min. Overall, 14 different complexes were synthesized to improve luminescence using our previously proposed strategy to boost luminescence through ligand diversification, specifically by applying it to quaternary europium complexes with at least one DBM (1,3-diphenylpropane-1,3-dionate) ligand. DBM is a strong absorbant of UV radiation that can dissipate energy through nonradiative channels; thus, it is a useful molecular scaffold for sunblockers and cosmetics.

NMR and luminescence experiments reveal the structure and symmetry adaptation of a europium ionic liquid to solvent polarity.

By combining NMR data (nuclear Overhauser effect and pseudocontact shifts) with luminescence measurements, we uncover how the structure of an anionic europium complex adapts to different solvent polarities as a result of the different relative proximities of the ion pairs. In nonpolar solvents, the detected contact ion pairs, CIPs, indicate that the ions remain in proximity, with the molecular cation, and then perturbing and distorting the coordination polyhedron of the anion complex to a low symmetry configuration, which promotes luminescence. Differently, solvent separated ion pairs occur in polar solvents, indicating that the molecular ions have been disconnected.

Substantial Intensification of the Quantum Yield of Samarium(III) Complexes by Mixing Ligands: Microwave-Assisted Synthesis and Luminescence Properties.

A luminescence quantum yield of 7.8% was obtained for a quaternary mixed-ligand samarium complex; this value is higher than those previously reported in the literature for such complexes in solution. The complex was prepared by microwave-assisted synthesis in 15 min with a yield of 69%; that is, ∼400 times faster than the usual synthesis that required 4 days and led to a yield of only 30%.