Circularly polarized phosphorescence (CPP) is a spin-forbidden radiative process, and its underlying mechanism is not comprehensively understood, mainly due to the limited examples of efficient triplet emission from small chiral organic molecules with well-defined structures. Here we investigate a pair of chiral enantiomers, R- and S-BBTI, that feature highly distorted spiral ring-locked heteroaromatics with heavy iodine atoms. These chiral molecules are found to exhibit large dissymmetry factors up to 0.013 and emit near-infrared CPP with an efficiency of 4.2% and a lifetime of 119 μs in dimethyl sulfoxide solution excited by ultraviolet irradiation. Their crystals show efficient CPP with 7.0% quantum efficiency and a lifetime of 166 μs. Extensive experimental chiroptical investigations combined with theoretical calculations reveal an efficient spin-flip process that modulates the electron and magnetic transition dipole moments to enhance CPP performance. Moreover, the phosphorescence of R/S-BBTI is oxygen-sensitive and photoactivatable in dimethyl sulfoxide. Therefore, R/S-BBTI can be applied for hypoxia imaging in cells and tumours, expanding the application scope of CPP materials.

圆偏振磷光（CPP）是一种自旋禁阻辐射过程，其潜在机制尚不完全清楚，主要是由于具有明确结构的小手性有机分子的有效三重态发射的例子有限。在这里，我们研究了一对手性对映体， R - 和S -BBTI，其特征是具有重碘原子的高度扭曲的螺旋锁环杂芳族化合物。这些手性分子表现出高达 0.013 的大不对称因子，并在紫外线激发的二甲亚砜溶液中发射近红外 CPP，效率为 4.2%，寿命为 119 μs。他们的晶体表现出高效的 CPP，量子效率为 7.0%，寿命为 166 μs。广泛的实验手性光学研究与理论计算相结合揭示了一种有效的自旋翻转过程，可以调节电子和磁跃迁偶极矩以增强 CPP 性能。此外， R / S -BBTI的磷光对氧敏感并且在二甲基亚砜中可光活化。因此， R / S -BBTI可应用于细胞和肿瘤的缺氧成像，扩大了CPP材料的应用范围。