Tunable Morphology and Mesophase Formation by Naphthalene-Containing Poly(aryl ether) Dendron-Based Low-Molecular-Weight Fluorescent Gels

Novel poly­(aryl ether) dendron-based low-molecular-weight organogelaters (LMWG) containing naphthalene units at the core have been synthesized, and the self-assembly of the system has been examined in a variety of solvents and solvent mixtures. The compounds readily form gels with attractive critical gel concentration values associated with gelation-induced enhanced emission (GIEE). In addition to the remarkable properties of the previously reported anthracene and pyrene analogues (Rajamalli, P.; Prasad, E. <i>Org. Lett.</i> <b>2011</b>, <i>13,</i> 3714 and Rajamalli, P.; Prasad, E. <i>Soft Matter</i> <b>2012</b>, <i>8,</i> 8896), the self-assembled systems exhibit distinctly different structure–property relationships. Unlike the reported ones, the present system forms sheetlike morphology in nonpolar solvent mixtures, giant vesicles in polar solvent mixtures, and lamellar or hexagonal columnar phases in single solvents. The unique properties of the self-assembled systems, which were analyzed through electron microscopic (SEM, TEM, AFM) and spectroscopic techniques (POM, fluorescence), are attributed to the replacement of anthracene/pyrene units by naphthalene units. The present work unravels the subtle role of minute structural change in altering the properties of LMWGs based on poly­(aryl ether) dendrons

Palladium-Catalyzed Dehydrogenative β‑Arylation of Simple Saturated Carbonyls by Aryl Halides

A versatile palladium-catalyzed synthesis of highly substituted α,β-unsaturated carbonyl compounds has been developed. In contrast to the known Heck-type coupling reaction of unsaturated carbonyl compounds with aryl halides, the present methodology allows the use of stable and readily available saturated carbonyl compounds as the alkene source. In addition, the reaction proceeds well with low catalyst loadings and does not require any expensive metal oxidants or ligands. A variety of saturated aldehydes, ketones, and esters are compatible for the reaction with aryl halides under the developed reaction conditions to afford α,β-unsaturated carbonyl compounds in good to excellent yields. A possible reaction mechanism involves a palladium-catalyzed dehydrogenation followed by Heck-type cross couplings

New Molecular Design Concurrently Providing Superior Pure Blue, Thermally Activated Delayed Fluorescence and Optical Out-Coupling Efficiencies

Simultaneous enhancement of out-coupling efficiency, internal quantum efficiency, and color purity in thermally activated delayed fluorescence (TADF) emitters is highly desired for the practical application of these materials. We designed and synthesized two isomeric TADF emitters, 2DPyM-<i>m</i>DTC and 3DPyM-<i>p</i>DTC, based on di­(pyridinyl)­methanone (DPyM) cores as the new electron-accepting units and di­(<i>tert</i>-butyl)­carbazole (DTC) as the electron-donating units. 3DPyM-<i>p</i>DTC, which is structurally nearly planar with a very small Δ<i>E</i>_ST, shows higher color purity, horizontal ratio, and quantum yield than 2DPyM-<i>m</i>DTC, which has a more flexible structure. An electro­luminescence device based on 3DPyM-<i>p</i>DTC as the dopant emitter can reach an extremely high external quantum efficiency of 31.9% with a pure blue emission. This work also demonstrates a way to design materials with a high portion of horizontal molecular orientation to realize a highly efficient pure-blue device based on TADF emitters