Effect of ß-Ketoiminato Ancillary Ligand Modification on Emissive Properties of New Iridium Complexes.

A series of new bis(benzo[h]quinolinato) Ir(III) complexes with modified ß-ketoiminato ancillary ligands were synthesized, and their electrochemical, photophysical properties were determined with the support of theoretical calculations. Moreover, all the synthesized heteroleptic Ir(III) complexes were examined as dopants of the host-guest type emissive layers in solution-processed phosphorescent organic light emitting diodes (PhOLEDs) of a simple structure. As expected on the basis of voltammetry measurements as well as DFT calculations, all the compounds appeared to be green emitters. Their examination showed that alteration of ß-ketoiminato ligand structure causes frontier orbitals' energy levels to be slightly changed, while significantly affecting photoluminescence and electroluminescence efficiencies of iridium phosphors containing these ligands. It was also found that modification of ancillary ligands might enhance charge trapping on the dopant, thus increasing its efficiency, especially in electroluminescence. From among the iridium complexes studied, the compound bearing 1-naphthyl group bonded to the nitrogen atom of the ancillary ligand proved to be the most efficient emitter. The PhOLED fabricated on the basis of this dopant has reached a luminance level of 16000 cd/m2, current efficiency close to 12 cd/A, and an external quantum efficiency around 3.2%.

Quantum-chemical studies of homoleptic iridium(III) complexes in OLEDs: fac versus mer isomers.

A series of facial fac-[Ir(5-R-bzq)3] and meridional mer-[Ir(5-R-bzq)3] Ir(III) complexes bearing benzo[h]quinoline-based ligands have been studied with the help of density functional theory (DFT) methods. A detailed electronic structure comparison of the two isomers has been addressed to point out the differences in their stability and photophysical properties. An influence of substituent impact on optical and electronic properties of Ir(III) homoleptic complexes was also explored by introducing into the cyclometalated ligands substituents characterized with different electronic properties, e.g., R = H, F, OPh, NMe2, C6F5, and p-C6H4-NPh2. The results herein show that fac and mer isomers exhibit remarkable differences in stability and photophysical properties. The introduction of different functional groups into bzq ligands, despite very similar geometrical structures, significantly affected HOMO and LUMO energy levels and energy gaps of the examined Ir(III) complexes.

Screening of a chemical library reveals novel PXR-activating pharmacologic compounds.

The pregnane X receptor (PXR) is one of the master regulators of xenobiotic transformation. Interactions between pharmacologic compounds and PXR frequently result in drug-to-drug interactions, drug-induced hepatotoxicity, and the development of drug-resistant phenotypes in cancer cells. Potential PXR-mediated effects on drug metabolism can be predicted using high-throughput methods to detect PXR transactivation. We used the reporter cell line nhrtox-hepg2 to screen an 1120-compound library of pharmacologic substances. Using a three-stage screening process combined with a quantitative structure-activity relationships (QSAR) analysis, we detected 16 novel, previously unreported PXR activators capable of upregulating CYP450 expression. For some of these compounds such as mycophenolic acid, leflunomide, and trifluridine, the observed interactions with PXR occurred at clinically significant concentrations and could provide potential mechanistic explanations for observed drug-to-drug interactions and drug-induced toxicity. A parallel QSAR analysis revealed significant correlation between the experimentally measured PXR-dependent bioactivity and the calculated molecular descriptors of the PXR activators.