推拉电子基团区域异构苯并咪唑的发射行为与力致荧光变色性能研究  

Research on Emission Behavior and Mechanofluorochromic Activity of Benzo[d]imidazoles with Region-isomerized Push-Pull Groups

作　　者：贾彦荣[1] 徐凯[1] 赵彦英[1] 倪华钢[1] 吴滢 夏敏[1] Jia Yanrong;Xu Kai;Zhao Yanying;Ni Huagang;Wu Ying;Xia Min(School of Chemistry and Chemical Engineering,Zhejiang Sci-Tech University,Hangzhou 310018;Ningbo Municipal Bureau of Ecology and Environment,Ningbo 315000)

机构地区：[1]浙江理工大学化学与化工学院,杭州310018 [2]宁波市生态环境局,宁波315000

出　　处：《化学学报》2023年第12期1716-1723,共8页Acta Chimica Sinica

基　　金：国家自然科学基金(No.22273086);金华市重大(重点)科学技术研究计划项目(No.2021-3-168)资助。

摘　　要：以芘基和4-腈基苯基为取代基,分别合成了两者在苯并咪唑环上N_(1)位与C_(2)位区域异构的两个化合物BIMNPy和BIM_(CPy),研究了两种化合物在溶液中以及固态下的荧光发射性质与力致荧光变色行为.在溶液中, BIM_(CPy)的荧光发射波长表现出中等幅度的正向溶剂变色效应,而BIMNPy的荧光发射波长则对溶剂极性的变化无响应.两种化合物的晶体在受力后均出现发射波长的蓝移,且在BIMNPy晶体上产生的力致荧光变色活性比在BIM_(CPy)晶体上更为显著.此外,BIMNPy的力致荧光变色性在溶剂熏蒸及热退火状态下均可逆,并在室温下具有部分自恢复特性;BIM_(CPy)的力致荧光变色性在溶剂熏蒸下可逆而在热退火处理时不可逆.根据示差热扫描、粉末与单晶衍射、发射衰变光谱以及理论计算的结果,对两种化合物发射行为差异性的原因进行了分析与探讨,认为溶液态下的差异起源于高能级电子激发态的发射特征不同而固态下的差异起源于分子堆积模式的区别,但推拉电子基团区域异构所引起的分子偶极矩以及π-共轭程度的变化则是异构体产生宏观性能不同的根本原因.Through the oxidation-cyclization of N-(4-cyanophenyl)-o-phenylenediamine and 1-pyrenylaldehyde or N-(1-pyrenyl)-o-phenylenediamine and 4-cyanobenzaldehyde in dimethyl sulfoxide under air,the two isomers BIMNPy and BIM_(CPy) with pyrenyl and 4-cyanophenyl interchanged at N_(1) and C_(2) position on benzo[d]imidazole core were prepared while the photophysical properties of the double isomers in both solution and solid state were investigated.In solution,the emission of BIM_(CPy) exhibited a moderate solvatochromic effect but the emission of BIMNPy was inert to the change of solvent polarity.The crystals of the two isomers displayed the blue-shifted mechanofluorochromic(MFC)behavior in response to force stimuli,but BIMNPy crystals possess the larger MFC activity.Moreover,the MFC on BIMNPy was reversible by fuming in solvent vapor or annealing and could be partly self-recovered at room temperature thanks to the less dense intermolecular interactions.However,the MFC on BIM_(CPy) was irreversible under annealing and could only be recovered by fuming due to the indispensability of solvent molecules to form crystal lattices.In aid of differential scanning calorimetry,powder and single crystal X-ray diffraction,emission decay spectra as well as theoretical calculations,the reasons for the different emission behavior of the two isomers in solution and solid state were explored.It was revealed that the S2 excited state with both intramolecular charge transfer(ICT)and local emission(LE)features may account for the sensitive solvatochromism of BIM_(CPy),while the S2 excited state with only LE emission feature may be responsible for the inert solvatochromism of BIMNPy.Moreover,the different solid-state emission performance and MFC activity should be attributed to the particular molecular packing in crystals of the two isomers.Fundamentally,the varied dipole moments and the distinguishingπ-conjugation extents induced by the region-isomerization of pyrenyl and 4-cyanophenyl with the push-pull electronic capability could be con

关 键 词：力致荧光变色 区域异构 苯并咪唑 芘基 分子堆积 

分 类 号：O626[理学—有机化学]