A surprising yet highly practical approach to improve the performance of a TADF exciplex blend is reported. Using the TSBPA donor and PO-T2T acceptor to form an exciplex, we are able to blue shift the emission, increase PLQY from 58 to 80%, and increase the device EQE from 14.8 to 19.2% by simply diluting the exciplex with an inert high triplet energy host materialhere either UGH-3 or DPEPO. These effects are explained in terms of an increasing donor–acceptor distance and associated charge separation, while different behaviors observed in the different hosts are attributed to different energy barriers to electron transfer through the host. We expect that the observed performance-enhancing effects of dilution will be general to different exciplex blends and host materials and offer a new way to optimize the electrical properties of exciplex emission layers with narrow blue emission.

New thermally activated delayed fluorescence (TADF) blue emitter molecules based on the known donor−acceptor−donor (D−A−D)type TADF molecule, 2,7-bis(9,9-dimethylacridin-10-yl)-9,9-dimethylthioxanthene-S,S-dioxide (DDMA-TXO2), are reported. The motivation for the present investigation is via the use of rational molecular design, based on DDMA-TXO2, to elevate the organic light emitting diode (OLED) performance and obtain deeper blue color coordinates. To achieve this goal, the strength of the donor (D) unit and acceptor (A) units have been tuned with methyl substituents. The methyl functionality on the acceptor was also expected to modulate the D−A torsion angle in order to obtain a blue shift in the electroluminescence. The effect of regioisomeric structures has also been investigated. Herein, we report the photophysical, electrochemical, and single-crystal X-ray crystallography data to assist with the successful OLED design. The methyl substituents on the DDMA-TXO2 framework have profound effects on the photophysics and color coordinates of the emitters. The weak electron-donating methyl groups alter the redox properties of the D and A units and consequently affect the singlet and triplet levels but not the energy gap (ΔE ST ). By systematically manipulating all of the aforementioned factors, devices have been obtained with acceptor-substituted III with a maximum external quantum efficiency of 22.6% and Commission Internationale de l'E ́clairage coordinates of (0.15, 0.18) at 1000 cd m −2 .

The first direct and straightforward nucleophilic fluoromethylation of organic compounds is reported. The tactic employs a "fleeting" lithium fluorocarbenoid (LiCHF) generated from commercially available fluoroiodomethane. Precise reaction conditions were developed for the generation and synthetic exploitation of such a labile species. The versatility of the strategy is showcased in ca. 50 examples involving a plethora of electrophiles. Highly valuable chemicals such as fluoroalcohols, fluoroamines, and fluoromethylated oxygenated heterocycles could be prepared in very good yields through a single synthetic operation. The scalability of the reaction and its application to complex molecular architectures (e.g., steroids) are documented.

The not so elusive carbenoid fluoroiodomethyllithium disclosed its electrophilic nature in an unprecedented direct and stereoselective fluorocyclopropanation of allylic alcohols.

An expeditious, high-yielding synthesis of rare α-fluoroepoxides and α-fluoroaziridines through the addition of the unkown fluoroiodomethyllithium (LiCHIF)formed via deprotonation the commercially available fluoroiodomethane with a lithium amide baseto carbonyl-like compounds is documented. The ring-closure reactions, leading to α-fluorinated three-membered heterocycles, rely on the diversely reactive C–I and C–F bonds. Excellent chemoselectivity was observed in the presence of highly sensitive functionalitiesaldehyde, ketone, nitrile, alkenewhich remained untouched during the homologation sequence.