π‑Conjugated Polymers Composed of BODIPY or Aza-BODIPY Derivatives Exhibiting High Electron Mobility and Low Threshold Voltage in Electron-Only Devices

We present efficient electron-transport materials based of polymers. π-Conjugated copolymers composed of boron dipyrromethene (BODIPY) or Aza-BODIPY were synthesized via the efficient Suzuki–Miyaura cross-coupling reaction of (2,5-bis­(2-(2-(2-(pyridin-2-yloxy)­ethoxy)­ethoxy)­ethoxy)-1,4-phenylene)­diboronic acid with each of the diiodo-substituted BODIPY and Aza-BODIPY. Synthesized polymers exhibited high solubility even in polar solvents such as acetic acid. Their electronic and optical properties were studied by cyclic voltammetry, UV–vis absorption, and photoluminescence spectroscopies. The absorption and photoluminescence spectra of the obtained polymers were red-shifted in comparison with the corresponding monomers due to the increase in the HOMO level by the formation of donor–acceptor interactions and the expansion of main-chain conjugations, explained by their cyclic voltammograms and theoretical calculations of the model compounds using the density-functional theory method. Finally, the electron mobilities of the polymers were determined from the space-charge-limited current with electron-only device structure of ITO/Ca/polymer/BCP/LiF/Al. As a result, owing to their high electron acceptability and strong stacking interaction among the BODIPY or Aza-BODIPY units, it was found that the mobilities for the polymers ((1.5–3.6) × 10^–4 [cm² V^–1 s^–1]) were much higher than the value of Alq₃ (5.8 × 10^–5 [cm² V^–1 s^–1]), and their threshold voltages (5–7 V) were much smaller than that of the Alq₃ device (12 V)

Cyclo‑<i>meta</i>‑phenylene Revisited: Nickel-Mediated Synthesis, Molecular Structures, and Device Applications

From a one-pot nickel-mediated Yamamoto-type coupling reaction of <i>m</i>-dibromobenzene, five congeners of [<i>n</i>]­cyclo-<i>meta</i>-phenylenes were synthesized and fully characterized. The [<i>n</i>]­cyclo-<i>meta</i>-phenylenes possessed a commonly shared arylene unit and intermolecular contacts but varied in packing structures in the crystalline solid state. Columnar assembly of larger congeners yielded nanoporous crystals with carbonaceous walls to capture minor protic or aliphatic solvent molecules. The concise and scalable synthesis allowed exploration of the macrocyclic hydrocarbons as bipolar charge carrier transport materials in organic light-emitting diode devices

Modular Synthesis of Aromatic Hydrocarbon Macrocycles for Simplified, Single-Layer Organic Light-Emitting Devices

A method for the modular synthesis of aromatic hydrocarbon macrocycles has been developed for base materials in single-layer organic light-emitting devices. The method with Ir-catalyzed direct C–H borylation and Suzuki–Miyaura coupling was concise and scalable, which allowed for a gram-scale preparation of aromatic hydrocarbon macrocycles that have bulky substituents at the periphery. The new arylated hydrocarbon macrocycles enabled a quantitative electro-optical conversion in organic light-emitting devices with a phosphorescent emitter, which is, notably, in a single-layer architecture consisting of two regions of doped and undoped materials. The highest external quantum efficiencies reached 24.8%, surpassing those of previous hydrocarbon base materials