ACQ‐to‐AIE Transformation: Tuning Molecular Packing by Regioisomerization for Two‐Photon NIR Bioimaging

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.

ACQ‐to‐AIE Transformation: Tuning Molecular Packing by Regioisomerization for Two‐Photon NIR Bioimaging

“…d) Single crystal structure, e) dimer structure, and f) molecular p-p stacking structures TBP-e-TPA. [25] Angewandte Chemie Zuschriften fluorescence signals (collected from 700-800 nm) from twophoton imaging irradiated by a NIR-II pulsed laser at 1040 nm displayed almost identical distribution with that of one-photon imaging (Figure 4 c). It was widely reported that 2PF microscopy (2PFM) shows greater penetration depth, lower photodamage, and better 3D resolution compared to one-photon microscopy.…”

Emerging Designs of Aggregation-Induced Emission Agents for Enhanced Phototherapy Applications

“…Various design strategies have been explored to create AIE agents with high ROS generating efficiency. 72,73 For example, a strong electron donor-acceptor interaction in the molecular skeleton facilitates ICT, thus leading to the enhanced singlet oxygen generation efficacy. 74 Based on these design strategies, Tang et al74 synthesized several zwitterionic compounds, BITT, BITB, ITT, and ITB, which consist of a dimethylaniline or triphenylamine moiety as the donor, thiophene fragment as a donor and π-bridge, double bond for the π-bridge, and a quaternary ammonium salt unit as acceptor.…”

Aggregation‐induced emission materials for nonlinear optics

“…The basic framework of the molecules consisted of the Dithieno[2,3‐a:3′,2′‐c]benzo[i]phenazine (TBP) and the twisted molecular rotor TPA. [ 170 ] From the TBP‐ e ‐TPA molecule with long‐range cofacial packing mode to the TBP‐ b ‐TPA with discrete cross packing mode (Figure 7(H)), the minor modification of the positions of TBP units arose the switch from ACQ to AIE due to the generation of steric hindrance. The AIE active TBP‐ b ‐TPA also expressed the marvelous 2PA property (Figure 7(I)).…”