### 巨型给-受体分子开关化合物的合成及性质研究

1. 中南大学化学化工学院 长沙 410083
• 投稿日期:2022-06-29 发布日期:2022-08-05
• 通讯作者: 徐海
• 基金资助:
国家自然科学基金(21975288); 国家重点研发计划子课题(2018YFC1800401)

### A Gaint Donor-Acceptor Molecular Switch Compound: Synthesis and Properties

Yuguang Sui, Jinrong Zhou, Pan Liao, Wenjie Liang, Hai Xu()

1. College of Chemistry and Chemical Engineering, Central South University, Changsha 410083
• Received:2022-06-29 Published:2022-08-05
• Contact: Hai Xu
• Supported by:
National Natural Science Foundation of China(21975288); National Key Research and Development Plan of China(2018YFC1800401)

A novel donor-acceptor (D-A) molecular switch compound (compound 1) in which porphyrin is the donor and fullerene is the acceptor was synthesized using a conformationally variable resorcin[4]arene cavitand as the molecular switch parent. As far as we know, this molecule is the largest D-A resorcin[4]arene cavitand (molecular weight: 3064.9966). In order to synthesize this D-A molecular switch, firstly, compounds 4 and 9 were synthesized by Sonogashira coupling and Suzuki coupling, respectively. Then, both compounds 4 and 9 react with compound 5 to obtain arm compounds 6 and 10. Considering the low yield in the process of synthesizing porphyrins, compound 6 was first reacted with resorcin[4]arene 11 to obtain compound 12. Undoubtedly, a by-product with two compound 6 arms simultaneously will be produced. So, compound 12 can be obtained in a higher yield by adding compound 6 in batches. Then compound 13 can be obtained by the Prato reaction, and finally, compound 1 can be obtained by reacting with porphyrin arm 10. The structure of 1 was thoroughly confirmed by 1H NMR spectroscopy (nuclear magnetic resonance spectroscopy), 13C NMR spectroscopy, 2D (two-dimensional) NMR spectroscopy and HRMS (high-resolution mass spectrometry). Under pH induction, compound 1 can undergo a conformational change from the original contracted state (vase) to the expanded state (kite). However, the conformational change of 1 cannot be induced under the conditions of lowering the temperature and introducing Zn2+. The reason for the pH-induced conformational change may be that the addition of acid causes the protonation of the N atom on the quinoxaline arm, which makes the formed electrostatic repulsion push the arms away from each other. In addition, the photophysical properties of 1 were also studied. The photophysical processes were investigated with steady-state UV-visible absorption and transient fluorescence spectroscopies. Compound 1 shows efficient intramolecular singlet-singlet energy transfer from the porphyrin moiety to the fullerene moiety. The rate constants and eﬃciency of the singlet-singlet energy transfer are calculated at 1.1×107 s-1 and 9.63%, respectively.