Single-walled carbon nanotubes (SWNTs) were subjected to alkylation using alkyl bromide and alkyl dibromide, and the photoluminescence (PL) properties of the resulting alkylated SWNTs were characterized. Two new PL peaks were observed along with the intrinsic PL peak at 976 nm when alkyl bromide was used (SWNT-Bu: ∼1095 and 1230 nm, SWNT-Bn: 1104 and 1197 nm). In contrast, the use of α,α'-dibromo-o-xylene as an alkyl dibromide primarily resulted in only one new PL peak, which was observed at 1231 nm. The results revealed that the Stokes shift of the new peaks was strongly influenced by the addition patterns of the substituents. In addition, the time-resolved PL decay profiles of the alkylated SWNTs revealed that the PL peaks possessing a larger Stokes shift had longer exciton lifetimes. The up-conversion PL (UCPL) intensity of the alkylated SWNTs at excitation wavelengths of 1100 and 1250 nm was estimated to be ∼2.38 and ∼2.35 times higher than that of the as-dispersed SWNTs, respectively.

Containing two nitrogen atoms, the electron-deficient pyrimidine ring has excellent coordinating capability with transition metal ions. However, compared with the widely used pyridine ring, applications of the pyrimidine ring in phosphorescent Ir(III) complexes are rare. In this research, two highly emissive pyrimidine-based mononuclear Ir(III) complexes and their corresponding dinuclear Ir(III) complexes were prepared with a simple one-pot reaction. The incorporation of the second Ir(III) center can lead to dramatic differences of both photophysical and electrochemical properties between the mono- and dinuclear complexes. Besides, these properties can also be fine-tuned with different substituents. Theoretical calculations have also been performed to understand their photophysical behaviors. The electroluminescent investigations demonstrate that the pyrimidine-based mono- and dinuclear Ir(III) complexes could show impressive device performance. The vacuum-deposited organic light-emitting diode (OLED) based on the mononuclear Ir(III) complex exhibited an external quantum efficiency (EQE) of 16.1% with almost no efficiency roll-off even at 10 000 cd m. More encouragingly, the solution-processed OLED based on the dinuclear Ir(III) complex achieved the outstanding EQE, current efficiency (CE), and power efficiency (PE) of 17.9%, 52.5 cd A, and 51.2 lm W, respectively, representing the highest efficiencies ever achieved by OLEDs based on dinuclear Ir(III) complexes.

Simple trifunctional Ir(III) ppy-type asymmetric phosphorescent emitters with ambipolar character are reported, which afford highly efficient OLEDs.

Several phosphorescent Ir III ppy-type complexes (ppy ¼ 2-phenylpyridine anion) bearing dimesitylboron (B(Mes) 2 ) units have been designed and some of them have been newly prepared. By changing the substitution positions with different electronic characters that can manipulate the electron-accepting ability of the attached B(Mes) 2 moieties, the direction of the metal-to-ligand charge transfer (MLCT) process for these Ir III complexes can be either retained or shifted, which can provide a new strategy toward phosphorescent color tuning. Through computational studies, shifting the substitution position of the B(Mes) 2 moiety on the organic ligand, some electronic features, such as the electron injection/ electron transporting (EI/ET) properties and charge transport balance, can also be conferred to the phosphorescent Ir III complexes to give excellent electroluminescent (EL) characteristics. Highly efficient red phosphorescent bis(5-(dimesitylboryl)-2-phenylpyridinato)iridium(acetylacetonate) (Ir-B-1) based on the above notion shows a very good compatibility with the choice of host materials which can furnish maximum current efficiency (h L ) of 22.2 cd A À1 , external quantum efficiency (h ext ) of 14.7% and power efficiency (h P ) of 21.4 lm W À1 for the devices constructed with the conventional host materials. So, these exciting results will not only provide both the systematic guidelines for the phosphorescent color variation on the Ir III complexes with B(Mes) 2 units as well as a deeper insight into the conventional color-tuning approach on ppy-type Ir III complexes, but also offer a simple outlet to afford unique electronic features to these phosphorescent emitters to show admirable EL performance.

The host–guest complexes formed with [6]cycloparaphenyleneacetylene ([6]CPPA) and its anthracene‐containing derivative ([6]CPPAs) hosts and fullerene C70 guest were explored by density functional calculations. Besides two previously reported configurations in which C70 guest is standing or lying in the cavity of the host, we found a new kind of configuration in which C70 guest is half‐lying in the cavity of the host. More interestingly, the calculated results revealed that the fine‐tuning deformations occur readily during the formations of the complexes, suggesting that both [6]CPPA and [6]CPPAs are highly elastic host molecules. The large host–guest binding energies indicate that both two host molecules, [6]CPPA and [6]CPPAs, have excellent encapsulation ability for C70 guest, and the [6]CPPAs even has much better encapsulation ability for C70 than [6]CPPA. Furthermore, the host–guest interactions regions were detected and visualized in real space based on the electron density and reduced density gradient. Additionally, 1H NMR spectra of those three different kinds of configurations mentioned earlier have been calculated with gage‐independent atomic orbital method, which may be helpful for further experimental characterizations in future. Copyright © 2014 John Wiley & Sons, Ltd.