29 Feb 06:39
by Daniel Joven-Sancho,
Andrea Echeverri,
Nathalie Saffon-Merceron,
Julia Contreras-García,
Noel Nebra
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
by Tao Hua,
Nengquan Li,
Zhongyan Huang,
Youming Zhang,
Lian Wang,
Zhanxiang Chen,
Jingsheng Miao,
Xiaosong Cao,
Xinzhong Wang,
Chuluo Yang
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.