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29 Feb 06:39

An Organocopper(III) Fluoride Triggering C−CF3 Bond Formation

by Daniel Joven-Sancho, Andrea Echeverri, Nathalie Saffon-Merceron, Julia Contreras-García, Noel Nebra
An Organocopper(III) Fluoride Triggering C−CF3 Bond Formation

The first organocopper(III) fluoride, [PPh4][CuIII(CF3)3F] (2), has been isolated and authenticated. Despite its stability, 2 reacts with alkynylsilanes leading to industrially relevant trifluoromethylalkynes (RC≡CCF3). Mechanistic investigations, including the trapping of [PPh4][CuIII(CF3)3(C≡CPh)] (4a ), validates the operability of a CuI/CuIII redox shuttle in oxidative C−C couplings occurring through hitherto elusive organocopper(III) fluorides.


Abstract

Copper(III) fluorides are catalytically competent, yet elusive, intermediates in cross-coupling. The synthesis of [PPh4][CuIII(CF3)3F] (2), the first stable (isolable) CuIII−F, was accomplished via chloride addition to [CuIII(CF3)3(py)] (1) yielding [PPh4][CuIII(CF3)3Cl(py)] (1⋅Cl), followed by treatment with AgF. The CuIII halides 1⋅Cl and 2 were fully characterized using nuclear magnetic resonance (NMR) spectroscopy, single crystal X-ray diffraction (Sc-XRD) and elemental analysis (EA). Complex 2 proved capable of forging C−CF3 bonds from silyl-capped alkynes. In-depth mechanistic studies combining probes, theoretical calculations, trapping of intermediate 4a ([PPh4][CuIII(CF3)3(C≡CPh)]) and radical tests unveil the key role of the CuIII acetylides that undergo facile 2e reductive elimination furnishing the trifluoromethylated alkynes (RC≡CCF3), which are industrially relevant synthons in drug discovery, pharma and agrochemistry.

29 Feb 06:39

Narrowband Near‐Infrared Multiple‐Resonance Thermally Activated Delayed Fluorescence Emitters towards High‐Performance and Stable Organic Light‐Emitting Diodes

by Tao Hua, Nengquan Li, Zhongyan Huang, Youming Zhang, Lian Wang, Zhanxiang Chen, Jingsheng Miao, Xiaosong Cao, Xinzhong Wang, Chuluo Yang
Narrowband Near-Infrared Multiple-Resonance Thermally Activated Delayed Fluorescence Emitters towards High-Performance and Stable Organic Light-Emitting Diodes

A molecular design strategy has been developed to achieve both near-infrared emission and narrow full-width at half maximum of multi-resonance thermally activated delayed fluorescence emitters. Record-high external quantum efficiencies of nearly 30 %, and exceptional operational stability (LT97>39084 h) are realized simultaneously in the corresponding NIR organic light-emitting diodes (OLEDs).


Abstract

Multiple-resonance thermally activated delayed fluorescence (MR-TADF) materials are highly coveted for their high efficiency and narrowband emission in organic light-emitting diodes (OLEDs). Nevertheless, the development of near-infrared (NIR) MR-TADF emitters remains a formidable challenge. In this study, we design two new NIR MR-TADF emitters, PXZ−R−BN and BCz−R−BN, by embedding 10H-phenoxazine (PXZ) and 7H-dibenzo[c,g]carbazole (BCz) fragments to increase the electron-donating ability or extending π-conjugation on the framework of para-boron fusing polycyclic aromatic hydrocarbons (PAHs). Both compounds emit in the NIR region, with a full-width at half-maximum (FWHM) of 49 nm (0.13 eV) for PXZ−R−BN and 43 nm (0.11 eV) for BCz−R−BN in toluene. To sensitize the two NIR MR-TADF emitters in OLEDs, a new platinum complex, Pt-1, is designed as a sensitizer. The PXZ−R−BN-based sensitized OLEDs achieve a maximum external quantum efficiency (EQEmax) of nearly 30 % with an emission band at 693 nm, and exceptional long operational stability with an LT97 (time to 97 % of the initial luminance) value of 39084 h at an initial radiance of 1000 mW sr−1 m−2. The BCz−R−BN-based OLEDs reach EQEmax values of 24.2 % with an emission band at 713 nm, which sets a record value for NIR OLEDs with emission bands beyond 700 nm.