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Three novel thermally activated delayed fluorescence (TADF) emitters, named MCZ-B-DTM, MCZ-P2-DTM and MCZ-P3-DTM are designed and synthesized for fabricating blue emission devices. The position of nitrogen atom in pyridine ring is varied relative to the donor unit and the presence of CH⋯N hydrogen bonding in MCZ-P3-DTM is confirmed by theoretic simulation and 1H NMR analysis. Due to the introduction of CH⋯N hydrogen bonding between donor and acceptor, the dihedral angles, photophysical properties, together with thermal stabilities, of the targeted compounds are regulated ingeniously. As a consequence, MCZ-P3-DTM displays an increase of the molar extinction coefficient obviously and offers a higher PLQY of 60.1%. The TADF device adopting MCZ-P3-DTM as emitter shows a maximum external quantum efficiency (EQE) of 12.1%, which is superior to those of MCZ-B-DTM and MCZ-P2-DTM, demonstrating the introducing of intramolecular hydrogen bonding interactions between donor and acceptor is an efficient strategy for future structural design of TADF emitters.

Intramolecular through-space charge transfer (TSCT) excited state has been exploited for developing thermally activated delayed fluorescence (TADF) emitters, while the adjustment of excited state dynamics by conformational engineering is still rare. Herein, we designed a series of AIE-active TADF emitters, bearing triphenylamine as donor and phenyl ketone as acceptor unit, and the evolution of charge transfer from through-bond to through-space is realized by controlling the relative position of the donor and acceptor units. Upon transforming the charge transfer categories from through-bond to through-space, the reverse intersystem crossing (RISC) rate is progressively improved by virtue of the narrower energy split between singlet and triplet states (ΔEST), meanwhile, the restricted intramolecular motion suppresses the non-radiative decay effectively, resulting in obviously improved luminescence efficiency. Appointing a bipolar blue TADF material as host to sensitize these emitters, solution-processed organic light-emitting diodes (OLEDs) based on TSCT emitter 1TCPM-Cz achieve maximum current efficiency (CE) of 35.5 cd A−1 and external quantum efficiency (EQE) of 13.3%, respectively, which is higher than that of through-bond charge transfer (TBCT) analogues. The work demonstrates a convenient design strategy to achieve high-performance TSCT emitters by regulating the conformation of the donor and acceptor.

Reactive sulfur species (RSS), primarily containing glutathione (GSH), cysteine (Cys), hydrogen sulfide (H2S) and hydrogen polysulfides (H2Sn, n > 1), were crucial endogenous biological signal molecules. Among them, H2S and H2Sn played extremely momentous roles in many physiological and pathological processes. Limited by the vivo environmental diversity and complexity, it was highly desirable to rely on the single fluorescence probe platform to visualize H2Sn and H2S according different fluorescence signals. Herein, we reported a two-photon excited fluorescent probe MC-Sn that had the following merits: (Ⅰ) ratiometric and colorimetric: reducing detection errors and conducting visual analysis; (Ⅱ) two-photon microscope: better performance in vivo and vitro imaging; (Ⅲ) two specific sulfide reaction sites: studying on the mutual transformation of H2Sn and H2S in biological systems. Furthermore, take advantages of low cytotoxicity (cell viability ≥ 85.99%), low limit of detection (21 nM), significant photostability, excellent pH stability, quick response behavior (175 s) and high penetration depth (110 μm), MC-Sn can be employed to visualize endogenous and exogenous H2Sn and H2S in cells, liver tissues and zebrafish.