物理化学学报2019，Vol.35Issue(6)：637-643,7.DOI:10.3866/PKU.WHXB201807004
通过增强电荷转移激发态构建激发态下稳定的基于氰基二苯乙烯的E/Z构型
Stabilization of the E/Z Configuration for Cyanostilbene-based Luminogens by Enhanced Charge Transfer Excited State
摘要
Abstract
The E/Z isomerization reaction is found extensively in most organic molecules containing double bond unit.This limits their practical application as luminescent materials partly,especially under photoirradiation.Therefore,it is important to obtain E/Z isomers with stable configuration in the excited state after photoirradiation.It is well known that cyanostilbene and its analogues play an important role in the development of organic opto/electronic materials.The substituted cyano group on C =C double bonds has strong electron-withdrawing ability and large steric hindrance,which benefits the formation of donor-acceptor (D-A) structures and formation of intramolecular charge transfer.In our previous work,we reported a triphenylamine-cyanostilbene molecule (TPNCF) formed by modifying the cyanostilbene structure with triphenylamine,which maintained a stable E/Z configuration as a film and in high polar solvents.According to solvatochromism mechanisms and the results of theoretical calculations,we proposed that the charge transfer (CT) excited state between the triphenylamine donor and cyanostilbene acceptor groups induced the stable configuration of the E-and Z-isomers under photoirradiation.Under irradiation,the E/Z isomerization process occurring at a higher energy locally excited (LE) state was suppressed by a rapid internal conversion process from the LE to CT state.This work inspired us to provide a universal and effective molecular design strategy by modifying D-A substituents on double bonds that can successfully stabilize E/Z isomers.To further confirm that the CT excited state induced stable E-and Z-isomers in the cyanostilbene structure under photoirradiation,we designed and synthesized a donor-acceptor phenoxazine-cyanostilbene molecule (PZNCF) and successfully characterized its two E/Z isomers.In comparison with the reported TPNCF molecule,the in-situ NMR and UV spectra of E-and Z-isomers of PZNCF demonstrated that the E/Z isomerization rate became slower under photoirradiation,which indicated that the stronger electron-donating group of phenoxazine substituted in the cyanostilbene structure induced a more stable E/Z isomer configuration in its excited state.DFT calculations and photophysical results indicated that a stronger CT state was generated in both E-and Z-isomers of PZNCF.This further confirmed our hypothesized mechanism where the stable E/Z configuration can be obtained under photoirradiation by forming a suitable donor-acceptor structure to suppress the E/Z isomerization reaction in the LE state by a rapid internal crossing process from the LE to CT state.This molecular design strategy is of great significance to organic photochemistry and photoelectronics for molecules with double bond units.关键词
E/Z构型/电荷转移激发态/氰基二苯基乙烯/给受体结构/局域激发态Key words
E/Z configuration/Charge transfer excited state/Cyanostilbene/Donor-acceptor structure/Locally excited state分类
化学化工引用本文复制引用
董玉杰,许晨东,王士昭,李维军,宋庆宝,张诚..通过增强电荷转移激发态构建激发态下稳定的基于氰基二苯乙烯的E/Z构型[J].物理化学学报,2019,35(6):637-643,7.基金项目
The project was supported by the China Postdoctoral Science Foundation (2018M632498),the Zhejiang Provincial Postdoctoral fellowship,China(Z71101009),the National Natural Science Foundation of China (51603185,51673174),and the Zhejiang Provincial Natural Science Foundation,China(LY17E030001).中国博士后科学基金(2018M632498),浙江省博士后基金(Z71101009),国家自然科学基金(51603185,51673174),浙江省自然科学基金(LY17E030001)资助项目 （2018M632498）
