New N^N and N^C luminescent ligands with solvatochromic behavior and their iridium complexes were synthesized, characterized and investigated.

The effect of the emission layer deposition method on the characteristics of OLEDs was studied on the example of the europium mixed ligand complex Eu(tta)3DPPZ (tta: 2-thenoyltrifluoroacetone, DPPZ: dipyrido[3,2-a:2’c,3’c-c]phenazine), which...

In this work nine novel heteroleptic Ir(III) complexes of general formulae [Ir(N^C#) 2 (O^O#)] containing four different cyclometallating and four β-diketonate ligands were synthesized and fully characterized. Six of them display phosphorescence in the deep red and NIR regions with quantum yields reaching 24.6 % in degassed solution for one of the NIR emitters. Variation in the nature of orthometalating ligands results in dramatic changes in photophysical behavior: the compounds containing 2phenylpyridine (N^C1) and 2-(benzo[b]thiophen-2-yl)pyridine ( N^C2) ligands give non-emissive complexes, whereas those with methyl 2-phenylquinoline-4-carboxylate (N^C3) and 6-(benzo[b]thiophen-2-yl)phenanthridine) (N^C4) are luminescent, but display different character of electronic transitions respon-sible for absorption and emission. Complexes with the N^C3 ligand luminesce from 3 LC excited state and do not change their emission characteristics upon variations in the nature of βdiketonates. On the contrary, the compounds based on the N^C4 cyclometalating ligand emit from the excited state with considerable contribution of 3 MLCT character and show systematic bathochromic shift of absorption and emission bands upon increase in electron donicity of O^O# ligands. This conclusion was supported by DFT and TD-DFT calculations and by the analysis of correlations between the 13 C chemical shift of the diketonate C(H) carbon and emission maxima of the compounds under study.

Three novel luminescent Eu(III) complexes, Eu1–Eu3, have been synthesized and characterized with CHN analysis, mass-spectrometry and 1H NMR spectroscopy. The complexes display strong emission in dichloromethane solution upon excitation at 405 and 800 nm with a quantum yield from 18.3 to 31.6%, excited-state lifetimes in the range of 243–1016 ms at 20 °C, and lifetime temperature sensitivity of 0.9%/K (Eu1), 1.9%/K (Eu2), and 1.7%/K (Eu3). The chromophores were embedded into biocompatible latex nanoparticles (NPs_Eu1–NPs_Eu3) that prevented emission quenching and kept the photophysical characteristics of emitters unchanged with the highest temperature sensitivity of 1.3%/K (NPs_Eu2). For this probe cytotoxicity, internalization dynamics and localization in CHO-K1 cells were studied together with lifetime vs. temperature calibration in aqueous solution, phosphate buffer, and in a mixture of growth media and fetal bovine serum. The obtained data were then averaged to give the calibration curve, which was further used for temperature estimation in biological samples. The probe was stable in physiological media and displayed good reproducibility in cycling experiments between 20 and 40 °C. PLIM experiments with thermostated CHO-K1 cells incubated with NPs_Eu2 indicated that the probe could be used for temperature estimation in cells including the assessment of temperature variations upon chemical shock (sample treatment with mitochondrial uncoupling reagent).

An approach to increase the efficiency of europium-based OLEDs was proposed through the formation of a mixed-ligand complex. The design of a series of europium complexes, together with an optimization of the solution deposition, including the host selection, as well as the variation of the solvent and deposition parameters, resulted in a noticeable increase in OLED luminance. As a result, the maximum luminance of the Eu-based OLED reached up to 700 cd/m2, which is one of the highest values for an Eu-based solution-processed OLED. Finally, its stability was investigated.