Jingyun Tan

Helicenes are circularly polarized luminescence (CPL)-active but suffer from a fundamental tradeoff between fluorescence quantum yield (Φ_F) and luminescence dissymmetry factor (|g_lum|). Herein, we present a strategy combining lateral π-extension and helical elongation in carbazole-embedded helicenes to address this challenge. Specifically, π-extended diaza[7]helicene (1) and diaza[9]helicene (2) were synthesized and characterized, revealing nearly a 2-fold increase in Φ_F and a 6-fold enhancement in |g_lum| from 1 to 2. This approach offers a new pathway for high-performance CPL emitters.

A benzo[rst]pentaphene (BPP) substituted by an isopropoxy group (BPP-OiPr) was synthesized in a facile manner. Its photophysical properties were investigated by UV–vis absorption and fluorescence spectroscopy in compassion to pristine BPP and its oxidation product, benzo[rst]pentaphene-5,8-dione (BPP-dione). BPP-OiPr exhibited a significantly enhanced photoluminescence quantum yield (PLQY), reaching 73% in comparison to pristine BPP (13%). BPP-dione, when compared to the parent BPP, also displayed improved absorption and emission from the first excited singlet (S₁) state with a PLQY of 62% and an intramolecular charge-transfer character. The rod-like nano- to microcrystals as well as longer wires of these BPPs were also revealed by scanning electron microscopy. The intriguing optical properties of BPP and its derivatives may lead to their application as fluorophores.

Photosensitizers to precise target and change fluorescence upon light illumination could accurately self-report where and when the photosensitizers work, enabling us to visualize the therapeutic process and precisely regulate treatment outcomes, which is the unremitting pursuit of precision and personalized medicine. Here, we report self-immolative photosensitizers by adopting a strategy of light-manipulated oxidative cleavage of C═C bonds that can generate a burst of reactive oxygen species, to cleave to release self-reported red-emitting products and trigger nonapoptotic cell oncosis. Strong electron-withdrawing groups are found to effectively suppress the C═C bond cleavage and phototoxicity via studying the structure-activity relationship, allowing us to elaborate NG1-NG5 that could temporarily inactivate the photosensitizer and quench the fluorescence by different glutathione (GSH)-responsive groups. Thereinto, NG2 with 2-cyano-4-nitrobenzene-1-sulfonyl group displays excellent GSH responsiveness than the other four. Surprisingly, NG2 shows better reactivity with GSH in weakly acidic condition, which inspires the application in weakly acidic tumor microenvironment where GSH elevates. To this end, we further synthesize NG-cRGD by anchoring integrin α_vβ₃ binding cyclic pentapeptide (cRGD) for tumor targeting. In A549 xenografted tumor mice, NG-cRGD successfully deprotects to restore near-infrared fluorescence because of elevated GSH in tumor site, which is subsequently cleaved upon light irradiation releasing red-emitting products to report photosensitizer working, while effectively ablating tumors via triggered oncosis. The advanced self-immolative organic photosensitizer may accelerate the development of self-reported phototheranostics in future precision oncology.

Double helicenes are appealing chiral frameworks. Their π‐extension is desirable to achieve (chir)optical response in the visible and near‐infrared (NIR) region, but access to higher double [n]helicenes (n≥8) has remained challenging. Herein, we report an unprecedented π‐extended double [9]helicene (D9H), unambiguously revealing its structure by single‐crystal X‐ray diffraction.D9Hshows remarkable NIR emission from 750 to 1100 nm with a high photoluminescence quantum yield of 18 %. In addition, optically pureD9Hexhibits panchromatic circular dichroism with a notable dissymmetry factor (g_CD) of 0.019 at 590 nm, which is among the highest in the visible region for reported helicenes.

Double helicenes are appealing chiral frameworks. Their π‐extension is desirable to achieve (chir)optical response in the visible and near‐infrared (NIR) region, but access to higher double [n]helicenes (n≥8) has remained challenging. Herein, we report an unprecedented π‐extended double [9]helicene (D9H), unambiguously revealing its structure by single‐crystal X‐ray diffraction.D9Hshows remarkable NIR emission from 750 to 1100 nm with a high photoluminescence quantum yield of 18 %. In addition, optically pureD9Hexhibits panchromatic circular dichroism with a notable dissymmetry factor (g_CD) of 0.019 at 590 nm, which is among the highest in the visible region for reported helicenes.

The synthesis of a class of contorted electron-deficient polycyclic aromatic hydrocarbons (PAHs) has been achieved by a one-pot bay annulation of perylene diimide involving a mild Suzuki coupling and subsequent air-mediated, ambient-light-induced photocyclization. X-ray crystallography unambiguously confirmed the contorted PAH structure bearing four imide groups. The photophysical and electronic properties of these contorted PAHs were also analyzed, showing a high fluorescence quantum yield of 86% and moderate electron mobility of 0.017 cm² V^–1 s^–1.

Herein we present a synthesis of an S-shaped double helicene with fused imide moieties, achieving a contorted aromatic diimide (DHDI) with good fluorescence properties in both solution and the solid state. DHDI demonstrates distinct mechanofluorochromism from yellow to green emission under grinding of its crystalline powder.

This work describes a facile yet powerful approach to energy-transfer NMOF (nanoscale metal–organic framework) fabrication for ratiometric peroxynitrite (ONOO ⁻ ) sensing.