Abstract:
Conventional photosensitizers used in photodynamic therapy often suffer from aggregation-caused quenching (ACQ) due to their planar structure. This study presents the design and synthesis of a donor-acceptor-donor (D-A-D) photosensitizer with aggregation-induced emission (AIE) properties, which effectively eliminates the ACQ problem. The photosensitizers were synthesized using a Suzuki coupling and Knoevenagel condensation reaction, with triphenylamine as the donor and dicyano vinyl and 2-(2,6-dimethyl-4H-pyran-4-ylidene)malononitrile as acceptors. The donor was connected with a thiophene, 2,1,3-benzothiadiazole, and double bond spacers. Novel 7 photosensitizers were obtained with more than 40%yield. Photosensitizers with spacers containing electron-donating or withdrawing effects could enhance the absorption properties of photosensitizers compared to a neutral phenyl spacer which showed absorption at 530 nm compared to 475 nm, and this effect was further increased with a double bond to maximum of 558 nm. The synthesized photosensitizers showed AIE enhancement in nonpolar solvents, exhibiting a bright yellow to red fluorescence in the range of 550 nm to 655 nm which was influenced by effect of mentioned spacers. However, they exhibited low singlet oxygen generation ability in water as less than 5% ABDA was consumed in 6 minutes. Future work will focus on adjusting the structure to increase AIE properties while maintaining good photophysical properties. This could potentially lead to the development of more efficient photosensitizers for PDT