华东师范大学Jinquan Chen课题组的一项最新研究提出了通过螺环连接的分子促进近统一三线态的生成。这一研究成果发表在2021年11月17日出版的国际学术期刊《德国应用化学》上。

螺环连接的双色荧光分子系统在三线态激发态产生方面具有优势。首先，两个发色团被拉近到一个不能通过其他连接获得的近距离，促进了螺环连接介导的电荷转移（CT）。其次，螺环的正交性抑制了FRET型非辐射失活，高刚性又极大地抑制了振动能量耗散。目前已知的最高系间跨越（ISC）速率常数1.0×10¹¹ s^-1是在螺-双二苯甲酮骨架上实现的。

因此，该课题组人员设想，通过稳定螺环电子转移状态，合理设计由富电子的二苯醚作为螺环CT供体、缺电子的双萘酮作为螺环CT受体组成的螺环化合物家族（SCT），可以进一步提高三线态的产生效率。通过对CT和高能三线态之间的能级进行微调，研究人员获得了近统一的三线态量子产率，并通过超快光谱和量子化学计算揭示了潜在的系间跨越机制。最后，研究人员还在SCT分子中展示了三线态增敏的潜在应用。

他们的发现表明，具有增强的螺环电荷转移的螺环-双色荧光分子系统保证了高效的三线态生成，并代表了一种强大的无重原子三线态敏化剂的设计策略，且具有可预测的ISC特性。

附：英文原文

Title: Near-Unity Triplet Generation Promoted via Spiro-Conjugation

Author: Meng Lv, Xicun Lu, Yanrong Jiang, Marí, David Casanova, Haitao Sun, Zhenrong Sun, Jianhua Xu, Youjun Yang, Jinquan Chen

Issue&Volume: 2021-11-17

Abstract: Spiro-linked bichromophoric molecular systems are superior for triplet excited state generation. First, the two chromophores are tethered into a close proximity not accessible via alternative linkage, promoting spiro-conjugation mediated charge-transfer (CT). Second, the spiro-orthogonality inhibit FRET-type non-radiative deactivation and high rigidity largely suppresses vibronic energy dissipation. An intersystem crossing (ISC) rate constant of 1.0×10  11  s  -1  was previously registered with a spiro-bis-benzophenone scaffold. We envisage that triplet generation efficiency could be further enhanced by stabilizing the spiro-CT state and rationally designed a family of spiro-compounds (SCTs), which consist of electron-rich diphenyl ether as the spiro-CT donor and electron-deficient dinaphthyl ketone as the spiro-CT acceptor. Through fine-tuning of the energy level between the CT and high energy triplet states, near-unity triplet generation quantum yield was achieved and the underlying ISC mechanism is revealed by using ultrafast spectroscopy and quantum chemical calculations. Finally, potential triplet sensitizing application was demonstrated in SCTs. Our findings suggest that spiro-bichromophoric molecular system with an enhanced spiro-charge transfer warrants efficient triplet generation and represents a powerful design strategy of heavy-atom-free triplet sensitizers with predictable ISC property.

DOI: 10.1002/anie.202113190

Source: https://onlinelibrary.wiley.com/doi/10.1002/anie.202113190