三亚苯及其卤键复合晶体的螺旋结构和超长寿命室温磷光  

The helical structures and ultralong lifetime room-temperature phosphorescence of triphenylene and its halogen-bonding cocrystals

作　　者：刘正扉 陈雪 高妍 朱慧敏 吴文新 张家新 晋卫军[1] Zheng-Fei Liu;Xue Chen;Yan Gao;Huimin Zhu;Wen-Xin Wu;Jiaxin Zhang;Wei-Jun Jin(College of Chemistry,Beijing Normal University,Beijing 100875,China)

机构地区：[1]北京师范大学化学学院,北京100875

出　　处：《中国科学：化学》2022年第6期989-1002,共14页SCIENTIA SINICA Chimica

基　　金：国家自然科学基金(编号:21974011)资助项目。

摘　　要：本文利用σ-穴键、π-穴键、氢键以及π–π堆积相互作用,组装了具有P2_(1)2_(1)2_(1)空间群的三亚苯(TP)、2-溴三亚苯(2-BrTP)晶体,以及三亚苯与三氯–三氟苯和三溴–三氟苯的复合晶体(TClTP和TBrTP).所组装的晶体材料都具有超长寿命的室温磷光,发光主要源于自旋–禁阻和对称性禁阻的双禁阻跃迁行为.另外,固态基体中分子间的相互作用,也提供了外在的刚性化条件,减弱了非辐射跃迁途径.内重原子溴或复合晶体中外重原子氯和溴增强了磷光光谱中禁阻的0–0跃迁.并且,由于氯原子具有较弱的自旋–轨道耦合作用,TP和TClTP具有同一数量级的磷光寿命,大约700 ms,并分别呈现红色和黄色余辉.而2-BrTP和TBrTP中,溴原子具有较强的自旋–轨道耦合作用,大大抑制了荧光,磷光寿命达到100 ms以上,分别呈现紫红色和亮黄色余辉.氯和溴的自旋–轨道耦合作用具有纯电子特征,不涉及电子–振动耦合.在2-BrTP晶体中,Br作为取代基和内重原子微扰剂,破坏了三亚苯的对称性,除了使得0–0跃迁增强外,磷光光谱的振动精细结构变得更差.相对于三亚苯晶体,复合晶体起到了调制磷光特征的作用.此外,相对于低温磷光光谱,晶体的室温磷光光谱普遍向红移.这应该归因于以下方面:第一,低温条件下,取向极化来不及弛豫到稳定态,发光分子仍然具有未弛豫的弗兰克–康登(Franck–Condon)态,发射波长较短;第二,相对于离散态的低温溶液,由固态密堆积所导致的各种分子间相互作用导致向红移.Crystal triphenylene(TP),2-bromotriphenylene(2-BrTP)with P2_(1)2_(1)2_(1) space group,and the cocrystals of triphenylene with 1,3,5-trichloro-/1,3,5-tribromo-2,4,6-trifluorobenzene(TClTP and TBrTP)were assembled by using theσ-hole bond,π-hole bond,hydrogen bond andπ–πstacking interaction.The assembled crystal materials have ultralong phosphorescence lifetime at room temperature,which originates mainly from the double forbidden transition behavior of spin-and symmetry-forbidden T_(1)→S_(0).The interactions between the molecules in solid matrix also provide external rigid conditions,which weakens the nonradiation pathway.The internal heavy atom,bromine in 2-BrTP or the external heavy atoms,chlorine and bromine in the cocrystal(TClTP and TBrTP)enhance the forbidden 0–0 transition in the phosphorescence spectra.Moreover,the chlorine atom has weaker spin–orbital coupling,so TP and TClTP crystals have almost same phosphorescence lifetime of about 700 ms,and they show red and yellow afterglow,respectively.While the bromine atom has stronger spin–orbital coupling in 2-BrTP and TBrTP crystals,the fluorescence is greatly inhibited,and phosphorescence lifetime of more than 100 ms is detected.They show magenta and light-yellow afterglow,respectively.The spin–orbital coupling of chlorine and bromine atoms has pure electronic characteristics and does not involve vibronic coupling in nature.In addition,bromine,as the substituent and internal heavy-atom perturber in the 2-BrTP crystal,reduces high symmetry of triphenylene and makes the vibrational fine-structure of phosphorescence spectra become poor in addition to enhancing the 0–0 transition.It is also noticed that compared with the TP crystal,the cocrystal plays a role in modulating the phosphorescence characteristics.In addition,compared with the low-temperature phosphorescence spectra,the room-temperature phosphorescence spectra of the crystals produce red-shift effect generally.This should be attributed to the following aspects.First,at low temperature,th

关 键 词：室温磷光 卤键 π-穴键 超长余辉 三亚苯 复合晶体 螺旋 

分 类 号：O641.3[理学—物理化学] O76[理学—化学]