物理化学学报

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具有聚集诱导发光特性的新型铂(II)金属配合物及其光激发的自敏化氧化反应

王士昭, 李维军, 俞越, 刘进, 张诚   

  1. 浙江工业大学化学工程学院, 绿色化学合成技术国家重点实验室培育基地, 科技部能源材料及应用国际科技合作基地, 杭州 310014
  • 收稿日期:2019-02-19 修回日期:2019-03-18 录用日期:2019-03-21 发布日期:2019-03-28
  • 通讯作者: 张诚, 李维军 E-mail:czhang@zjut.edu.cn;liwj@zjut.edu.cn
  • 基金资助:
    国家自然科学基金(51603185,51673174),浙江省自然科学基金(LQ19E030016,LY19E030006,LZ17E030001),国家博士后科学基金(2018M632498)及浙江省博士后奖学金(Z71101009)资助项目

Aggregation-Induced Emission Property of a Novel Pt(II) Metal Complex and Its Self-Sensitized Oxidation Reaction in Photo-Excitation State

WANG Shizhao, LI Weijun, YU Yue, LIU Jin, ZHANG Cheng   

  1. State Key Laboratory Breeding Base of Green Chemistry-Synthesis Technology, College of Chemical Engineering, International Science & Technology Cooperation Base of Energy Materials and Application, Zhejiang University of Technology, Hangzhou 310014, P. R. China
  • Received:2019-02-19 Revised:2019-03-18 Accepted:2019-03-21 Published:2019-03-28
  • Contact: ZHANG Cheng, LI Weijun E-mail:czhang@zjut.edu.cn;liwj@zjut.edu.cn
  • Supported by:
    The project was supported by the National Natural Science Foundation of China (51603185, 51673174), Zhejiang Provincial Natural Science Foundation of China (LQ19E030016, LY19E030006, LZ17E030001), China Postdoctoral Science Foundation (2018M632498), and the Zhejiang Provincial Postdoctoral fellowship, China (Z71101009).

摘要: 现如今过渡金属配合物因其优良的物理、化学特性应用前景很好,但实际应用中浓度淬灭严重影响其性能。聚集诱导发射(AIE)效应是一种常见的解决措施,但基于金属配合物方面的报道还相对较少。本论文中报道了一个种具有AIE效应的咪唑类金属Pt(II)配合物PtP2IM,通过单晶解析了其结构。在可见光下,该金属配合物可以发生光氧化反应生成一种新的咪唑/苯酰胺基类配合物PtPIMO。通过单晶解析、核磁共振、紫外-可见光谱等测试手段对该反应进行了研究。电子顺磁共振(EPR)测量结果显示PtP2IM的光氧化反应属于单态氧氧化反应。密度泛函理论(DFT)计算显示单线态氧是由配合物MLCT的能量转移激发产生的。去除氧后,PtP2IM具有良好的光稳定性和明显的AIE特性。从晶体堆积中,我们发现PtP2IM的AIE特性可以归因于RIR效应即分子内旋转受限效应。聚集状态下,PtP2IM仍可以发生单线态氧的光氧化反应。综上所述,我们报道了一种具有AIE特性的新型铂(II)金属络合物PtP2IM,光激发下可以发生自敏化反应。本工作旨在研究具有AIE性质的过渡金属配合物的基本光化学和光物理性质。

关键词: 金属铂(II)配合物, 光氧化反应, 单线态氧, 金属-配体电荷跃迁, 聚集诱导发光

Abstract: The excited states of transition metal complexes with a wide range of photochemical and photophysical properties have attracted considerable attention recently. However, the luminescence property is affected by concentration quenching in practical applications. Aggregation-induced emission (AIE) is an effective strategy to solve this problem. In this work, a new imidazole-based N^C^N Pt(Ⅱ) metal complex, PtP2IM, with the AIE property was synthesized and characterized according to its single crystal structure. Under visible light, we found that the metal complex undergoes a photo-oxidation reaction with the generation of a new red-emitting, imidazole/benzoylimino-based N^C^N' Pt(Ⅱ) metal complex, PtPIMO, which was also confirmed by the crystal structure. Additional studies on the reaction process and conditions of this photo-oxidation reaction were conducted using different methods, such as NMR, UV-Vis spectroscopy, and so on. The experimental results showed that the change from PtP2IM to PtPIMO gradually occurred, and the new photochemical reaction was finally concluded as the C=C double bond in either one of the two imidazole rings of the PtP2IM complex was attacked by oxygen to generate a new complex, PtPIMO, under photoirradiation in air. Electron paramagnetic resonance (EPR) measurements demonstrated the production of singlet oxygen, which is an excited state of oxygen with a high energy. Through the density functional theory (DFT) calculations, the electronic transition was determined to be a metal to ligand charge transfer (MLCT) in which more energy could transfer from the triplet excited state of PtP2IM to the ground-state oxygen to generate singlet oxygen (1O2) with a high intersystem crossing (ISC) efficiency due to the spin-orbit coupling of Pt heavy atoms. When large amounts of the singlet capture agent, triethylenediamine (TEDA) were added, the previously observed UV-Vis spectra change that corresponded to the photo oxidation reaction was not detected, which means that the photo-oxidation reaction observed in the case of PtP2IM was because of the oxidation by singlet oxygen. When oxygen was removed, excellent photostability and an obvious aggregation-induced emission (AIE) were observed for PtP2IM with the luminescent quantum efficiency of PtP2IM in solution and as a film at~3% and~20%, respectively. Based on the packing structure in the crystal, we observed that there were no strong intermolecular interactions, such as π-π or Pt-Pt interactions. Additionally, many intermolecular CH-π bonds between the two adjacent PtP2IM molecules were observed, which could effectively limit the rotation of the peripheral phenyl group linked to the imidazole ring. Thus, the AIE property of PtP2IM was attributed to the restricted intramolecular rotation (RIR) effect of the peripheral flexible phenyl group that was linked to the imidazole ring in the solid state in which the vibration of multiple peripheral benzene rings was effectively suppressed. This decreased the non-radiative transition rate and induced the high luminescent quantum efficiency. In the aggregation state, PtP2IM still demonstrated the photo-oxidation reaction by singlet oxygen. Thus, we report a new Pt(Ⅱ) metal complex, PtP2IM, with the AIE property that can undergo an uncommon photo-oxidation reaction in the photo-excitation state. This work aimed to elucidate the basic photochemical and photophysics of transition metal complexes with the AIE property.

Key words: Pt(II) metal complex, Photo-oxidation reaction, Singlet oxygen, MLCT, AIE

MSC2000: 

  • O644