Through-space conjugated molecules are interesting building blocks for the construction of functional materials that allow multi-dimensional transport of carrier and energy.However,the well explored through-space conjugated molecules are quite limited,which defers their structure-property correlation establishment and wide-scale application.In this review,we introduce a kind of newly-emerging folded tetraphenylethene derivatives featuring through-space conjugation.Their synthesis,crystal and electronic structures,and optical properties are described,and their representative applications as bipolar charge-transporting materials in organic light-emitting diodes and as single-molecule wires in molecular devices are presented,which are anticipated to provide guidance for the further expansion of through-space conjugated systems.
Tetraphenylethene (TPE) is a popular luminogen characterized by aggregation-induced emission and has been widely used to construct solid-state emissive materials. In this work, two thermally stable polymers (P1 and P2) consisting of TPE conjugated to the 2,7-positions of fluorene and carbazole, respectively, are synthesized and characterized. Both polymers are weakly fluorescent in solutions but show greatly enhanced emission as the aggregate formation, presenting an aggregation-enhanced emission feature. Two kinds of polymer light-emitting diodes are fabricated utilizing P1 and P2 as emitters (EML) (device I: ITO/PEDOT:PSS (45 nm)/PVK:EML (1:1 wt%, 55 nm)/TPBI (38 nm)/Ca:Ag; device II: ITO/PEDOT:PSS (45 nm)/ PVK:OXD-7:EML (3:1:3 wt%, 55 nm)/TPBI (38 nm)/Ca:Ag). The device II of P2 shows the best performances, affording a maximum luminance of 6500 cd/m 2 and a high peak efficiency of 2.11 cd/A.
HE BaiRongYE ShangHuiGUO YanJuCHEN BinXU XiaoFeiQIU HuaYuZHAO ZuJin
Two novel AIE-active salicylaldehyde azine(SAA) derivatives with a typical excited-state intramolecular proton transfer(ESIPT) process are prepared by introducing electron-withdrawing and donating groups at para-position of phenolic hydroxyl group(CN-SAA and TPA-SAA). The effect of the proton activity in SAA framework on their optical behaviors is investigated spectroscopically. The results from NMR and solvation measurements show that the proton of phenolic hydroxyl group has higher activity when there are electron-withdrawing groups, and the absorption and fluorescence spectra in buffers with different pH also provide the same results. After inviting F. as a nucleophilic probe, this proton activity difference in CN-SAA and TPA-SAA becomes more obvious. The potential application of both molecules is investigated. TPA-SAA exhibits good quantitative sensing ability towards F. with a fluorescence "turn-on" mode, whereas the aggregates of TPA-SAA can selectively and sensitively detect Cu2+ in aqueous solution. From these results, a structure-property relationship is established: the occurrence of ESIPT process will become much easier when linking electron-withdrawing groups at the para-position of phenolic hydroxyl group(e.g., CN-SAA),and it is better to introduce electron-donating groups to enhance the sensing ability towards ions(e.g., TPA-SAA). This work will provide guidance for further design and preparation of AIE-active luminogens with ESIPT process for sensing applications.
Tetraphenylethene(TPE)is a popular luminogen characterized by aggregation-induced emission and has been widely used to construct solid-state emissive materials.In this work,two thermally stable polymers(P1 and P2)consisting of TPE conjugated to the 2,7-positions of fluorene and carbazole,respectively,are synthesized and characterized.Both polymers are weakly fluorescent in solutions but show greatly enhanced emission as the aggregate formation,presenting an aggregation-enhanced emission feature.Two kinds of polymer light-emitting diodes are fabricated utilizing P1 and P2 as emitters(EML)(device I:ITO/PEDOT:PSS(45 nm)/PVK:EML(1:1 wt%,55nm)/TPBI(38 nm)/Ca:Ag;device II:ITO/PEDOT:PSS(45 nm)/PVK:OXD-7:EML(3:1:3 wt%,55 nm)/TPBI(38nm)/Ca:Ag).The device II of P2 shows the best performances,affording a maximum luminance of 6500 cd/m2and a high peak efficiency of 2.11 cd/A.
HE BaiRongYE ShangHuiGUO YanJuCHEN BinXU XiaoFeiQIU HuaYuZHAO ZuJin
