Using lithium carbonate-based electron injection structures in high-performance inverted organic light-emitting diodes.

A lithium carbonate-based bi-layered electron injection layer was introduced into inverted organic light-emitting diodes (OLEDs) to reduce operation voltages and achieve carrier balance. Ultraviolet photoemission spectroscopy was used to confirm the existence of an interfacial dipole between the organic and lithium carbonate layers, which is a dominating factor related to the device performance. The respective maximum efficiencies of 15.9%, 16.9%, and 8.4% were achieved for blue, green, and red phosphorescent inverted OLEDs with identical architectures, indicating that carrier balance was easily obtained. Moreover, adoption of this sophisticated electron injection layer design resulted in respective turn on voltages of only 3.4 V, 3.2 V, and 3.2 V. Furthermore, the inverted OLEDs equipped with silicon dioxide nanoparticle based light-extraction films achieved an approximately 1.3 fold efficiency improvement over pristine devices due to the low refractive index of the silicon dioxide nanoparticles along with an effective scattering function. The blue, green, and red inverted OLEDs with the nanocomposite layer achieved respective peak efficiencies of 20.9%, 21.3%, and 10.1%.

Pt(II) metal complexes tailored with a newly designed spiro-arranged tetradentate ligand; harnessing of charge-transfer phosphorescence and fabrication of sky blue and white OLEDs.

Tetradentate bis(pyridyl azolate) chelates are assembled by connecting two bidentate 3-trifluoromethyl-5-(2-pyridyl)azoles at the six position of pyridyl fragment with the tailored spiro-arranged fluorene and/or acridine functionalities. These new chelates were then utilized in synthesizing a series of Pt(II) metal complexes [Pt(Ln)], n = 1-5, from respective chelates L1-L5 and [PtCl2(DMSO)2] in 1,2-dimethoxyethane. The single-crystal X-ray structural analyses were executed on 1, 3, and 5 to reveal the generalized structures and packing arrangement in crystal lattices. Their photophysical properties were measured in both solution and solid state and are discussed in the context of computational analysis. These L1-L5 coordinated Pt(II) species exhibit intense emission, among which complex 5 shows remarkable solvatochromic phosphorescence due to the dominant intraligand charge transfer transition induced by the new bis(pyridyl azolate) chelates. Moreover, because of the higher-lying highest occupied molecular orbital of acridine, complex 5 can be considered as a novel bipolar phosphor. Successful fabrication of blue and white organic light-emitting diodes (OLEDs) using Pt(II) complexes 3 and 5 as the phosphorescent dopants are reported. In particular, blue OLEDs with 5 demonstrated peak efficiencies of 15.3% (36.3 cd/A, 38.0 lm/W), and CIE values of (0.190, 0.342) in a double-emitting layer structure. Furthermore, a red-emitting Os(II) complex and 5 were used to fabricate warm-white OLEDs to achieve peak external quantum efficiency, luminance efficiency, and power efficiency values as high as 12.7%, 22.5 cd/A, and 22.1 lm/W, respectively.

Design, synthesis, and biological evaluation of pyrrolo[2,1-c][1,4]benzodiazepine and indole conjugates as anticancer agents.

A series of novel pyrrolo[2,1-c][1,4]benzodiazepine (PBD) hybrids linked with indole carboxylates is described. These compounds were prepared by linking C-8 of 3 (DC-81) with an indole 2-carbonyl moiety (9) through carbon chain linkers to afford PBD hybrid agents 17-21 in good yields. Preliminary in vivo tests show that these hybrid agents have potent antitumor activity. The cytotoxic studies of the hybrid agents on human melanoma A2058 cells indicate most of the hybrids induced higher cytotoxicity, better DNA-binding ability, an increase in the apoptotic sub-G1 population, and a significant reduction in deltapsi(mt) relative to compound 3. In addition, DNA flow cytometric analysis shows that hybrids actively induce a marked loss of cells from the G2/M phase of the cell cycle, which progresses to early apoptosis as detected by flow cytometry after double-staining with annexin V and propidium iodide (PI). Thus, we suggest that the hybrid agents are potent inducers of cell apoptosis in A2058 cells.

Novel borane reduction of ether-protected aromatic lactams.

Borane reduction of ether-protected aromatic lactams produces 1-alkyl-1,2,3,4-tetrahydroquinolines (5 and 6) in excellent yields. This reaction provides a novel one-pot tandem process for reduction of amide group and N-protected groups. Experimental results demonstrate that the reaction proceeds through two consecutive elimination and reductions via two C-O bond cleavages to form the foresaid products.