4′-N,N-二乙氨基-3-羟基苯并黄酮激发态分子内质子转移机制的溶剂极性效应——实验和理论研究  

Experimental and Theoretical Investigations of Solvent Polarity Effect on ESIPT Mechanism in 4′-N,N-diethylamino-3-hydroxybenzoflavone

作　　者：姜羊林 陈明卿 梁民 尧奕歌 张燕 王鹏[1] 张建平[1] Yanglin Jiang;Mingqing Chen;Min Liang;Yige Yao;Yan Zhang;Peng Wang;Jianping Zhang(Key Laboratory of Advanced Light Conversion Materials and Biophotonics,Department of Chemistry,Renmin University of China,Beijing 100872,China;Information Technology Center,Renmin University of China,Beijing 100872,China;State Key Laboratory for Artificial Microstructure and Mesoscopic Physics,School of Physics,Peking University,Beijing 100871,China;State Key Laboratory of Elemento-organic Chemistry,College of Chemistry,Nankai University,Tianjin 300071,China)

机构地区：[1]中国人民大学化学系,先进光转换材料与生物光子学重点实验室,北京100872 [2]中国人民大学信息技术中心,北京100872 [3]北京大学物理学院,人工微观结构与介观物理国家重点实验室,北京100871 [4]南开大学化学学院,元素有机化学国家重点实验室,天津300071

出　　处：《物理化学学报》2025年第2期116-124,共9页Acta Physico-Chimica Sinica

基　　金：中央高校基本科研业务费专项资金;中国人民大学科学研究基金(21XNH085);中国人民大学校级计算平台支持;国家自然科学基金(21673289)资助项目。

摘　　要：激发态分子内质子转移(ESIPT)反应是一种重要的基础光化学反应,通常发生在具有分子内氢键的发色团中。3-羟基黄酮类衍生物(3-HFs)由于其广泛的天然来源和对环境极度敏感的荧光发光特性而备受关注。与3-HFs相比,4′-N,N-二乙氨基-3-羟基黄酮(D-HBF)具有扩展的共轭体系和大幅红移的吸收特性,而最新研究表明,由于具有ESIPT特性,它可以用作环境极性敏感的生物荧光探针。本研究通过采用多种光谱和理论计算方法,系统研究了D-HBF在极性不同的三种非质子型溶剂(环己烷、乙醚和四氢呋喃)中的ESIPT反应机制。研究结果显示,在这三种溶剂中均能观测到D-HBF的ESIPT典型双发射峰,而这些峰的相对比率受溶剂极性的调控。荧光动力学分析揭示,随着溶剂极性的增加,激发态中正向和反向的质子转移反应速率都降低,同时反向质子转移变得更占优势。该研究还通过密度泛函理论和含时密度泛函理论计算,比较了三种溶剂中D-HBF的基态和激发态分子内氢键的键长和键角参数,确定了ESIPT反应是激发态分子内氢键增强机制。计算结果表明,增加溶剂极性会导致处于S1态的D-HBF分子的3-羟基伸缩振动红外吸收频率向高波数移动,这证明了相应的N^(*)态的分子内氢键减弱。此外,电子密度分析显示,引入在4′-位的强给电子官能团(4′-N,N-二乙氨基)使得D-HBF在激发态下具有典型的分子内电荷转移特征。最后,势能曲线计算结果表明,在激发态下质子转移更容易发生,而溶剂极性增加会导致更高的质子转移势垒,从而阻碍了相应的ESIPT反应。吉布斯自由能分析进一步表明,溶剂极性增加使激发态快速质子转移更倾向于向N^(*)态移动。这项研究为D-HBF类衍生物作为环境极性敏感的生物探针的应用提供了理论基础。Excited-state intramolecular proton transfer(ESIPT)is a fundamental photoreaction of significant importance in both chemical and biological systems.This phenomenon typically occurs in chromophores featuring intramolecular hydrogen bonding.Among the molecules undergoing ESIPT,3-hydroxyflavone derivatives(3-HFs)have garnered significant attention due to their natural origins and environmentally responsive fluorescence properties.A particular 3-HF compound,4′-N,N-diethylamino-3-hydroxybenzoflavone(D-HBF),distinguished by its extendedπ-system and red-shifted electronic absorption,has recently been identified as a potent fluorescent probe highly sensitive to changes in environmental polarity.In this study,we systematically explored the ESIPT reaction mechanism of D-HBF in three aprotic solvents:cyclohexane,diethyl ether,and tetrahydrofuran,each possessing varying polarities.Our investigation involved a combination of spectroscopic and theoretical methods.In all three solvents,we observed the characteristic dual emission bands associated with ESIPT,with the intensity ratio of these bands being influenced by the solvent.As solvent polarity increased,we noted a decrease in the rates of both the forward and reverse proton transfer(PT)reactions based on our analysis of fluorescent kinetics.However,the reverse PT was favored.Through density functional theory(DFT)and time-dependent DFT(TDDFT)calculations of bond lengths and bond angles of the intramolecular hydrogen bond in these solvents,we confirmed that the ESIPT reaction in D-HBF is driven by the strengthening of the excited-state hydrogen bond.Notably,upon increasing solvent polarity,the intramolecular hydrogen bonds in the excited N^(*)state weakened,as evidenced by the up-shifted IR absorption frequency of the O―H stretching mode in the S1 state.Electron intensity analysis of frontier orbitals revealed characteristic intramolecular charge transfer(ICT)occurring in D-HBF upon photoexcitation,attributable to the introduction of a strong electron-donating group at t

关 键 词：4′-N N-二乙氨基-3-羟基苯并黄酮 激发态分子内质子转移 密度泛函理论/含时密度泛函理论 溶剂极性效应 荧光动力学 

分 类 号：O643[理学—物理化学]