Lanthanide Complexes with 2‑(Tosylamino)-benzylidene‑N‑(aryloyl)hydrazones: Universal Luminescent Materials

Lanthanide complexes Ln­(L1)­(HL1) (Ln = Lu, Yb, Er, Gd, Eu, Sm) and Ln­(L2)­(HL2) (Ln = Lu, Yb, Gd, Eu) with 2-(tosylamino)-benzylidene-N-(aryloyl)­hydrazones (H2L1, aryloyl = 2-hydroxybenzoyl; H2L2, aryloyl = isonicotinoyl) were obtained with the aim to explore them as new luminescent materials. They were found to form monomeric species independently on the aryloyl group, and their crystal structures were determined from single-crystal X-ray data (Yb­(L2)­(HL2)·0.5­(C2H5OH)), as well as from powder X-ray data by Rietveld refinement (Eu­(L1)­(HL1)). Ytterbium complexes exhibited intense luminescence, which allowed using them in host-free organic light-emitting diodes, which demonstrated remarkable efficiency of near infrared electroluminescence (50 μW/W) at low voltage (5 V). The special mechanism of europium luminescence quenching allowed using europium complexes as luminescent thermometers, which demonstrated very high sensitivity up to 12%/K. The theory of luminescence thermometry based on a three-level system was proposed, which allowed predicting sensitivity with high accuracy (error within 20%).