Search

Highlights: [•] Phosphorescence properties of a series of heteroleptic iridium(III) complexes have been theoretically investigated. [•] The –CF3 substitution at different positions at ancillary ligands may be an efficient approach of tuning emitting color. [•] The assumed complex 6 is considered to be potential candidate of blue-emitting material with high quantum yield. [Copyright &y& Elsevier]

Abstract: We report a quantum-chemistry analysis of four heteroleptic iridium(III) complexes (tfmppy)2Ir(tpip) [tfmppy=4-trifluoromethylphenylpyridine, tpip=tetraphenylimido-diphosphinate] (1), (tfmpyN3)2Ir(tpip) [tfmpyN3 =4-trifluoromethylphenyl-[1,2,3]-triazole] (2), (CN-pyN3)2Ir(tpip) [CN-pyN3 =4-cyanophenyl-[1,2,3]-triazole] (3) (ph-pta)2Ir(tpip) [ph-pta=2-(5-phenyl-[1,2,4]-triazol-3-yl)-pyridine] (4), which have been studied by using density functional theory (DFT) and time-dependent DFT (TDDFT) methods, to investigate their electronic structures, injection and transport properties, absorption and phosphorescence mechanism. The results reveal the different cyclometalated ligands have a large impact on the charge transfer performances of the studied complexes. The complex 4 possess better charge transfer abilities and balanced charge transfer rates, which is a potential candidate as blue-emitting material. [Copyright &y& Elsevier]

With the increase of heat treatment temperature, the angle between the fiber axis and the long axis of the pore decreases, the parallelism between the pores become more orderly, the short axis increases and the long axis decreases. [Display omitted] • In-situ SAXS study on the fractal structure change of a kind of pitch-based carbon fiber during HTT (1200 °C ∼ 1700 °C). • From the meridional to equatorial directions, carbon fiber exhibit pore and surface fractal at low (μ ≤ 71°) and high (μ ≥ 73°) azimuth angles, respectively. • During HTT from 1200 °C to 1700 °C, the fractal dimension gradually increases near the meridian direction, decreases in the equatorial direction, and first decreases and then increases in other directions. • Both pore fractal and surface fractal dimension gradually increase with increasing azimuth angle. High-temperature treatment (HTT) is a vital process to change the structure and improve the performance of pitch-based carbon fiber. The complexity of pore structure and their change during heating can be described by a mathematical concept of fractal. This short contribution reports an in-situ synchrotron radiation small angle X-ray scattering (SAXS) study on the fractal structure change of a kind of pitch-based carbon fiber during heating from 1200 °C to 1700 °C with Joule effect in a small furnace. The change of the fractal structure at different azimuth angles with temperature is revealed, and the corresponding mechanism is analyzed. [ABSTRACT FROM AUTHOR]