Yu Kexin, Pham Thanh Chung, Huang Jianjun, Li Yixuan, Van Meervelt Luc, Van der Auweraer Mark, Escudero Daniel, Dehaen Wim
Sustainable Chemistry for Metals and Molecules, Department of Chemistry, KU Leuven, Celestijnenlaan 200F, 3001 Leuven, Belgium.
Quantum Chemistry and Physical Chemistry, Department of Chemistry, KU Leuven, Celestijnenlaan 200F, 3001 Leuven, Belgium.
Molecules. 2025 Jun 20;30(13):2673. doi: 10.3390/molecules30132673.
BOPAM exhibits high fluorescence quantum yields, along with exceptional photostability, rendering it a promising platform for applications as fluorescence sensors. However, the development of BOPAM-based fluorophores with extended emission wavelengths remains limited, and the underlying mechanisms of fluorescence quenching via the population of dark twisted intramolecular charge transfer (TICT) excited states are not yet fully understood. To address these gaps, we synthesized a series of BOPAM derivatives by incorporating electron-donating groups at the boron atoms and the phenyl rings of the BOPAM core. The introduction of bromide, phenyl, and naphthyl groups preserved the intrinsic locally excited (LE) emission of BOPAM. In contrast, the incorporation of diphenylamine () and triphenylamine () moieties resulted in a red-shifted emission, attributed to an enhanced intramolecular charge transfer (ICT) process. Notably, in acetonitrile, exhibited weak fluorescence originating from a TICT state, which was populated via the S → TICT transition. Furthermore, the emission observed from was associated with a higher-lying excited state, likely the initially populated S state possessing a LE character. These findings not only introduce novel red-emissive BOPAM-based fluorophores, but also offer valuable insights into the role of the S state in governing fluorescence quenching mechanisms in BOPAM derivatives.
BOPAM具有高荧光量子产率以及出色的光稳定性，使其成为有前景的荧光传感器应用平台。然而，具有更长发射波长的基于BOPAM的荧光团的开发仍然有限，并且通过暗扭曲分子内电荷转移（TICT）激发态的填充实现荧光猝灭的潜在机制尚未完全理解。为了填补这些空白，我们通过在BOPAM核心的硼原子和苯环上引入供电子基团，合成了一系列BOPAM衍生物。溴、苯基和萘基的引入保留了BOPAM固有的局域激发（LE）发射。相比之下，二苯胺（）和三苯胺（）部分的引入导致发射红移，这归因于分子内电荷转移（ICT）过程的增强。值得注意的是，在乙腈中，表现出源自TICT态的弱荧光，该TICT态是通过S→TICT跃迁填充的。此外，从观察到的发射与更高能级的激发态相关，可能是最初填充的具有LE特征的S态。这些发现不仅引入了新型的基于BOPAM的红色发射荧光团，还为S态在控制BOPAM衍生物荧光猝灭机制中的作用提供了有价值的见解。
