image: Figure 1 | Strategy for diradicaloids design. a, Structure of the previously reported Chichibabin's hydrocarbon, TTM-TTM. b, Structure of the newly synthesized Chichibabin's hydrocarbon, TT-CzPh. c, Synthetic routes are toward TT-CzPh.
Credit: Ting Liu et al.
Diradicaloids, particularly Chichibabin hydrocarbons, have long been of interest in functional materials due to their unique electronic structures and strong spin-coupling effects, which endow them with narrow band gaps and excellent NIR light absorption—ideal properties for photothermal therapy. However, their intrinsic chemical instability and low luminescence efficiency have hindered practical biomedical applications. Though recent progress, such as the chlorine-substituted Chichibabin hydrocarbon TTM-TTM, achieved NIR emission (λem = 780 nm) and improved stability, its low PLQY (only 0.8%) restricted its use in optical imaging and precise therapy.
Recently, in a new paper published in Light: Science & Applications, led by Professor Alim Abdurahman, Professor Xiaomin Liu, and Professor Geyu Lu from the College of Electronic Science and Engineering, Jilin University, China, have been proposed a novel molecular design strategy. By breaking the alternating symmetry of the Chichibabin framework and introducing a mild donor unit, 3-substituted-9-phenyl-9H-carbazole (3PCz), they successfully synthesized a stable Chichibabin diradicaloid TT-CzPh with both excellent near-infrared (NIR) luminescent properties and ultra-high photothermal conversion efficiency (PCE). The TT-CzPh not only achieves a high photoluminescence quantum yield (PLQY) of 6.4% but also exhibits an ultra-high photothermal conversion efficiency of 87.5%. Its assembled water-soluble nanoparticles (TT-CzPh NPs) enable precise near-infrared imaging-guided tumor photothermal ablation in a 4T1 tumor-bearing mouse model. This opens new possibilities for Chichibabin's hydrocarbons in bioimaging and cancer phototherapy applications.
"It is worth considering whether replacing the four peripheral chlorine atoms of TTM-TTM with mild donors could further improve its photophysical properties. Based on this hypothesis, we skillfully incorporated 3-substituted-9-phenyl-9H-carbazole (3PCz) into the skeleton of TTM-TTM, resulting in a novel Chichibabin’s hydrocarbon derivative, TT-CzPh, which exhibits significantly improved luminescence. "
" In contrast, introducing the donor group 3PCz in TT-CzPh reduces electron-hole overlap, which lowers non-radiative losses and enhances oscillator strength. These two effects together contribute to TT-CzPh’s increased PLQY. Moreover, its extended outer structure provides protection, making its photostability ~4 times higher than TTM-TTM. Optimized photophysical properties particularly redshifted NIR emission and higher PLQY highlight its potential as a cancer phototherapeutic agent."
" We found that TT-CzPh exhibited a significantly bright fluorescent signal and a high PCE of 87.5%, making TT-CzPh an ideal candidate for bio-photothermal therapy applications. Based on this, we prepared water-soluble nanoparticles, TT-CzPh NPs, to explore biological applications. TT-CzPh NPs not only exhibit excellent NIR imaging performance but also achieve a PCE of up to 82%. Furthermore, their outstanding imaging capability effectively guided in vivo photothermal tumor therapy."
Journal
Light Science & Applications
Article Title
Efficient Luminescent Stable Chichibabin Diradicaloid for Near-infrared Imaging and Photothermal Therapy