The development of molecules with efficient dual-state emission in the red/NIR region is significant for their broader application prospects in the biological field, but still remains a great challenge. Guided by in-depth TDDFT calculations, herein we firstly demonstrate a phenyl-removing strategy in TPE-merged squaraine dyes for accessing intense red/NIR emissions in both solution and crystalline states, on the basis of fully decoding the bidirectional TICT/ESIPT mechanism. By removing one phenyl rotor in the TPE segment, both less TICT formation and phenyl rotations facilitate the brightest red emission (λ_em = 586/622 nm, Φ_PL = 57.5%) of SQHTPE in solution, while the reserved hydrogen-bonding packing and the ESIPT process guarantee the intense red/NIR emission (λ_em = 670 nm, Φ_PL = 51.2%) in its crystalline state. Moreover, efficient red bioimaging in HUVECs has been achieved via naked SQHTPE, which provides a new vision for directly applying squaraine dyes in biological applications.

中文翻译：

---

由TDDFT计算指导的在红色/近红外区域访问高效双态发射极的苯去除策略

在红色/近红外区域中具有有效双态发射的分子的开发对于它们在生物领域的更广阔的应用前景具有重要意义，但仍然是一个巨大的挑战。在深入的TDDFT计算的指导下，本文首先在完全解码双向TICT / ESIPT机制的基础上，首先演示了TPE合并的方酸类染料中的苯基去除策略，该溶液可在溶液态和结晶态中获得强烈的红色/ NIR发射。通过在TPE段中除去一个苯基转子，均不TICT形成和苯基的旋转促进最亮的红色发光（λ _EM =622分之586纳米，Φ _PL = 57.5％）的SQHTPE在溶液中，而保留的氢键填料和ESIPT过程保证了强烈的红色/ NIR发射（λ _EM = 670纳米，Φ _PL = 51.2％）在其结晶状态。此外，已经通过裸露的SQHTPE在HUVEC中实现了有效的红色生物成像，这为将方酸菁染料直接应用于生物应用提供了新的视野。