Supramolecular Architectures, Photophysics, and Electroluminescence of 1,3,4-Oxadiazole-Based Iridium(III) Complexes: From μ-Dichloro Bridged Dimer to Mononuclear Complexes

One μ-dichloro bridged diiridium complex and three mononuclear iridium(III) complexes based on the 1,3,4-oxadiazole derivatives as cyclometalated ligands and acetylacetonate (acac) or dithiolates O,O‘-diethyldithiophosphate (Et2dtp) or N,N‘-diethyldithiocarbamate (Et2dtc) as ancillary ligands have been synthesized and systematically studied by X-ray diffraction analysis. The results reveal that three mononuclear complexes all adopt distorted octahedral coordination geometry around the iridium center by two chelating ligands with cis-C−C and trans-N−N dispositions, which have the same coordination mode as the diiridium dimer. The dinuclear complex crystallizes in the monoclinic system and space group C2/c, whereas three mononuclear iridium complexes are all triclinic system and space group P1̄. In the stacking structure of the dimer, one-dimensional tape-like chains along the b-axis are formed by hydrogen bondings, which are strengthened by π stacking interactions between phenyl rings of 1,3,4-oxadiazole ligands. Then these chains assemble a three-dimensional alternating peak and valley fused wave-shape structure. In each stacking structure of three mononuclear complexes, two molecules form a dimer by the C−H···O hydrogen bondings, and these dimers are connected by π stacking interactions along the b-axis, constructing a zigzag chain. Then these zigzag chains are interacted by π stacking along the a-axis, building up a two-dimensional structure. All complexes emit green with emission wavelengths in the range of 501−535 nm, depending on the structures of cyclometalated ligands and ancillary ligands. Electroluminescent devices using complexes 2−4 as phosphorescent dopants have been fabricated. A high-efficiency green emission device with a maximum luminous efficiency of 5.26 cd/A at a current density of 1.38 mA/cm2 and a maximum brightness of 2594 cd/m2 at 15.5 V has been achieved using 2 as the emitter

Synthesis and Properties of Carbazole Main Chain Copolymers with Oxadiazole Pendant toward Bipolar Polymer Host: Tuning the HOMO/LUMO Level and Triplet Energy

Three new carbazole copolymers, poly(9-(2,5-diarene-[1,3,4]oxadiazole)-carbazole-alt-9-(2-ethylhexyl)-carbazole-3,6-diyl)s (P1), poly(9-(2,5-diarene-[1,3,4]oxadiazole)-2, 7-carbazole-alt-9-(2-ethylhexyl)-3, 6-carbazole-diyl)s (P2), and poly(9-(2,5-diarene-[1,3,4]oxadiazole)-carbazole-alt-9-(2-ethylhexyl)-carbazole-2,7-diyl)s (P3), were synthesized by the Suzuki coupling reaction. The copolymers were characterized by 1H NMR, 13C NMR, and elements analysis, and their molecular weights were estimated using gel permeation chromatography. The TGA and DSC results revealed their good thermal stability with high glass-transition temperatures (Tg) at 211 °C (P1), 194 °C (P2), and 208 °C (P3), respectively. The copolymers exhibited blue emission with significantly improved fluorescence quantum efficiencies compared to their analogous polymers. The triplet energies of P1, P2, and P3 were determined to be 2.52, 2.42, and 2.32 eV, respectively, from their phosphorescent spectra at 77 K. The HOMO/LUMO levels of the carbazole copolymers can be tuned by different coupling positions and substitution at the 9-position of carbazole. P1 by connecting carbazole units via their 3 (6) positions shifts the HOMO/LUMO levels to higher energy compared to P2 via 2 (7) positions, whereas replacing alkyl groups at the 9-position of carbazole with electron-withdrawing diaryl-1,3,4-oxadiazole group shifts the HOMO/LUMO levels to lower energy. Finally, polymer light-emitting diodes employing the P1−3 as host and bis(2,4-diphenylquinolinato-N,C2′)iridium(acetylacetonate) (Ir(ppq)2(acac)) as guest were constructed and characterized electrically

Supramolecular Architectures, Photophysics, and Electroluminescence of 1,3,4-Oxadiazole-Based Iridium(III) Complexes: From μ-Dichloro Bridged Dimer to Mononuclear Complexes

One μ-dichloro bridged diiridium complex and three mononuclear iridium(III) complexes based on the 1,3,4-oxadiazole derivatives as cyclometalated ligands and acetylacetonate (acac) or dithiolates O,O‘-diethyldithiophosphate (Et2dtp) or N,N‘-diethyldithiocarbamate (Et2dtc) as ancillary ligands have been synthesized and systematically studied by X-ray diffraction analysis. The results reveal that three mononuclear complexes all adopt distorted octahedral coordination geometry around the iridium center by two chelating ligands with cis-C−C and trans-N−N dispositions, which have the same coordination mode as the diiridium dimer. The dinuclear complex crystallizes in the monoclinic system and space group C2/c, whereas three mononuclear iridium complexes are all triclinic system and space group P1̄. In the stacking structure of the dimer, one-dimensional tape-like chains along the b-axis are formed by hydrogen bondings, which are strengthened by π stacking interactions between phenyl rings of 1,3,4-oxadiazole ligands. Then these chains assemble a three-dimensional alternating peak and valley fused wave-shape structure. In each stacking structure of three mononuclear complexes, two molecules form a dimer by the C−H···O hydrogen bondings, and these dimers are connected by π stacking interactions along the b-axis, constructing a zigzag chain. Then these zigzag chains are interacted by π stacking along the a-axis, building up a two-dimensional structure. All complexes emit green with emission wavelengths in the range of 501−535 nm, depending on the structures of cyclometalated ligands and ancillary ligands. Electroluminescent devices using complexes 2−4 as phosphorescent dopants have been fabricated. A high-efficiency green emission device with a maximum luminous efficiency of 5.26 cd/A at a current density of 1.38 mA/cm2 and a maximum brightness of 2594 cd/m2 at 15.5 V has been achieved using 2 as the emitter

Assembly of One-Dimensional Organic Luminescent Nanowires Based on Quinacridone Derivatives

The quinacridone derivatives N,N‘-dialkyl-1,3,8,10-tetramethylquinacridone (CnTMQA, n = 6, 10, 14) were used as building blocks to assemble luminescent nano- and microscale wires. It was demonstrated that CnTMQA with different lengths of alkyl chains display obviously different wire formation properties. C10TMQA and C14TMQA showed a stronger tendency to form 1-D nano- and microstructures compared with C6TMQA. The C10TMQA molecules could be employed to fabricate the wires with different diameters, which exhibited a size-dependent luminescence property. The emission spectrum of the C10TMQA wires with diameters of 200−500 nm shows a broad emission band at 560 nm and a shoulder at around 535 nm, while the emission spectrum of the C10TMQA wires with diameters of 2−3 μm reveals a narrower emission band at 563 nm. For the CnTMQA-based samples with different morphologies, the emission property change tendency agrees with that of the powder X-ray diffraction patterns of these samples

Chaperone-mediated autophagy prevents apoptosis by degrading BBC3/PUMA

<p>Autophagy is a potentially inimical pathway and together with apoptosis, may be activated by similar stress stimuli that can lead to cell death. The molecular cues that dictate the cell fate choice between autophagy and apoptosis remain largely unknown. Here we report that the proapoptotic protein BBC3/PUMA (BCL2 binding component 3) is a bona fide substrate of chaperone-mediated autophagy (CMA). BBC3 associates with HSPA8/HSC70 (heat shock 70kDa protein 8), leading to its lysosome translocation and uptake. Inhibition of CMA results in stabilization of BBC3, which in turn sensitizes tumor cells to undergo apoptosis. We further demonstrate that upon TNF (tumor necrosis factor) treatment, IKBKB/IKKβ (inhibitor of kappa light polypeptide gene enhancer in B-cells, kinase β)-mediated BBC3 Ser10 phosphorylation is crucial for BBC3 stabilization via blocking its degradation by CMA. Mechanistically, Ser10 phosphorylation facilitates BBC3 translocation from the cytosol to mitochondria. BBC3 stabilization resulting from either Ser10 phosphorylation or CMA inhibition potentiates TNF-induced apoptotic cell death. Our findings thus reveal that the selective degradation of BBC3 underlies the prosurvival role of CMA and define a previously unappreciated proapoptotic role of IKBKB that acts through phosphorylation-mediated stabilization of BBC3, thereby promoting TNF-triggered apoptosis.</p

Charge Carrier Transporting, Photoluminescent, and Electroluminescent Properties of Zinc(II)-2-(2-hydroxyphenyl)benzothiazolate Complex

Zinc(II)-2-(2-hydroxyphenyl)benzothiazolate complex is an excellent white-light-emitting material. Despite some studies devoted to this complex, no information on the real origin of the unusually broad electroluminescent (EL) emission is available. Therefore, we investigate photoluminescent and EL properties of the zinc complex. Orange phosphorescent emission at 580 nm was observed for the complex in thin film at 77 K, whereas only fluorescent emission was obtained at room temperature. Molecular orbitals, excitation energy, and emission energy of the complex were investigated using quantum chemical calculations. We fabricated the device with a structure of ITO/F16CuPc(5.5 nm)/Zn-complex/Al, where F16CuPc is hexadecafluoro copper phthalocyanine. The EL spectra varied strongly with the thickness of the emissive layer. We observed a significant change in the emission spectra with the viewing angles. Optical interference effects and light emission originating both from fluorescence and from phosphorescence can explain all of the observed phenomena, resulting in the broad light emission for the devices based on the Zn complex. We calculated the charge transfer integral and the reorganization energy to explain why the Zn complex is a better electron transporter than a hole transporter