Introducing Spiro-locks into the Nitrogen/Carbonyl System towards Efficient Narrowband Deep-blue Multi-resonance TADF Emitters.

The current availability of multi-resonance thermally activated delayed fluorescence (MR-TADF) materials with excellent color purity and high device efficiency in the deep-blue region is appealing. To address this issue in the emerged nitrogen/carbonyl MR-TADF system, we propose a spiro-lock strategy. By incorporating spiro functionalization into a concise molecular skeleton, a series of emitters (SFQ, SOQ, SSQ, and SSeQ) can enhance molecular rigidity, blue-shift the emission peak, narrow the emission band, increase the photoluminescence quantum yield by over 92 %, and suppress intermolecular interactions in the film state. The referent CZQ without spiro structure has a more planar skeleton, and its bluer emission in the solution state redshifts over 40 nm with serious spectrum broadening and a low PLQY in the film state. As a result, SSQ achieves an external quantum efficiency of 25.5 % with a peak at 456 nm and a small full width at half maximum of 31 nm in a simple unsensitized device, significantly outperforming CZQ. This work discloses the importance of spiro-junction in modulating deep-blue MR-TADF emitters.

Two-Channel Space Charge Transfer-Induced Thermally Activated Delayed Fluorescent Materials for Efficient OLEDs with Low Efficiency Roll-Off.

Enhancing the reverse intersystem crossing (RISC) process of thermally activated delayed fluorescent (TADF) emitters is an effective approach to realize efficient organic light-emitting diodes (OLEDs) with low efficiency roll-off. In this work, we designed two novel TADF emitters, SAT-DAC and SATX-DAC, via a spiro architecture. Efficient maximum external quantum efficiencies (EQEs) of 22.6 and 20.9% with reduced efficiency roll-off (EQEs of 17.9 and 17.0% at 1000 cd m-2) were achieved via a "two-RISC-channel" strategy. X-ray diffraction shows close donor (D)/acceptor (A) spacing and suitable D/A orientation in crystals of the two emitters favoring both intra- and intermolecular through-space charge transfer (TSCT) processes. Transient photoluminescence decay measurements show that both emitters have two RISC channels leading to kISCT exceeding 106 s-1. These results suggest that the "two-RISC-channel" design can be a novel approach for enhancing performance of TADF emitters, in particular at high excitation densities.

Yuccalides A-C, three new phenolic compounds with spiro-structures from the roots of Yucca gloriosa.

Three new phenolic compounds, yuccalides A-C (1-3), were isolated from the roots of Yucca gloriosa L., along with four known compounds (4-7). The structures of the new compounds were established by extensive NMR spectroscopic analyses. Inducible nitric oxide synthase (iNOS) mRNA levels induced by lipopolysaccharide (LPS) in mouse macrophage-like RAW 264.7 cells were effectively suppressed by compounds 2, 4, and 6, all of which had the (2R*, 3R*)-configuration. IL-1ß and IL-6 mRNA levels induced by LPS were significantly attenuated by compounds 4, 5, and 6, but not by 2.

Studies of Grafted and Sulfonated Spiro Poly(isatin-ethersulfone) Membranes by Super Acid-Catalyzed Reaction.

Spiro poly(isatin-ethersulfone) polymers were prepared from isatin and bis-2,6-dimethylphenoxyphenylsulfone by super acid catalyzed polyhydroxyalkylation reactions. We designed and synthesized bis-2,6-dimethylphenoxyphenylsulfone, which is structured at the meta position steric hindrance by two methyl groups, because this structure minimized crosslinking reaction during super acid catalyzed polymerization. In addition, sulfonic acid groups were structured in both side chains and main chains to form better polymer chain morphology and improve proton conductivity. The sulfonation reactions were performed in two steps which are: in 3-bromo-1-propanesulfonic acid potassium salt and in con. sulfuric acid. The membrane morphology was studied by tapping mode atomic force microscope (AFM). The phase difference between the hydrophobic polymer main chain and hydrophilic sulfonated units of the polymer was shown to be the reasonable result of the well phase separated structure. The correlations of proton conductivity, ion exchange capacity (IEC) and single cell performance were clearly described with the membrane morphology.