A research group led by Prof. XU Zhaochao from the Dalian Institute of Chemical Physics (DICP)
of the Chinese Academy of Sciences, as well as LIU Xiaogang’s group from Singapore University of Technology and Design, recently reported a reliable prediction method for twisted intramolecular charge transfer (TICT) formations in various fluorophores. Their study was published in Angew. Chem. Int. Ed.
TICT is a general photophysical process that can significantly quench the fluorescence and reduce the photo-stability of a dye. During such process, the donor or acceptor fragment will twist towards a perpendicular molecular conformation, resulting in a non-emissive and completely charge-separated species.
Therefore, the suppression of TICT can greatly enhance the fluorescence intensity and photo-stability, meeting the requirements of modern single molecular biosensing and super resolution bioimaging. However, it is still challenging to accurately predict the TICT formations in various systems towards the quantitative design of bright and stable fluorophores.
The researchers aim to deeply understand and explore the unique fluorescence mechanisms by combining experiments and calculations. Based on the preliminary mechanistic understanding, they realized accurate predictions in various TICT-related fluorophores.
According to the nature of TICT formation, researchers summarized S1 potential energy surfaces (PESs) of 13 types of fluorophores. They found the rotation barrier (ERB) and driving energy (EDE) is the key in describing TICT formations.
In particular, the fluorophore is more likely to stay in its bright state (LE or ICT states) with the larger ERB and EDE; If ERB > 0 and EDE < 0, the fluorophore will partly form TICT states; If ERB = 0 and EDE < 0, the fluorophore will significantly form TICT states, resulting in the substantial quenching of fluorescence. In short, the TICT formations can be accurately predicted via ERB and EDE.
Different types of S1 potential energy surface. (Image by WANG Chao)
This work is supported by National Natural Science Foundation of China and Chinese Academy of Sciences Special Research Assistant Project.