ACQ‐to‐AIE Transformation: Tuning Molecular Packing by Regioisomerization for Two‐Photon NIR Bioimaging
Yuanyuan Li, Shunjie Liu, Huwei Ni, Haoke Zhang, Hequn Zhang, Clarence Chuah, Chao Ma, Kam Sing Wong, Jacky W. Y. Lam, Ryan T. K. Kwok, Jun Qian, Xuefeng Lu, Ben Zhong Tang
Abstract
The traditional design strategies for highly bright solid-state luminescent materials rely on weakening the intermolecular π-π interactions, which may limit diversity when developing new materials. Herein, we propose a strategy of tuning the molecular packing mode by regioisomerization to regulate the solid-state fluorescence. TBP-e-TPA with a molecular rotor in the end position of a planar core adopts a long-range cofacial packing mode, which in the solid state is almost non-emissive. By shifting molecular rotors to the bay position, the resultant TBP-b-TPA possesses a discrete cross packing mode, giving a quantum yield of 15.6±0.2 %. These results demonstrate the relationship between the solid-state fluorescence efficiency and the molecule's packing mode. Thanks to the good photophysical properties, TBP-b-TPA nanoparticles were used for two-photon deep brain imaging. This molecular design philosophy provides a new way of designing highly bright solid-state fluorophores.