Preorganized helical chirality controlled homochiral self-assembly and circularly polarized luminescence of a quadruple-stranded Eu2L4 helicate
Preorganized helical chirality controlled homochiral self-assembly and circularly polarized luminescence of a quadruple-stranded Eu2L4 helicate
复制标题
四链 Eu2L4 螺旋的预组织螺旋手性控制同手性自组装和圆偏振发光
DOI：
10.1039/d0dt00062k
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发表时间：
2020-03-14
影响因子：
4
通讯作者：
Yan, Pengfei
中科院分区：
文献类型：
--
作者：
Han, Guoying;Zhou, Yanyan;Yan, Pengfei
由于β -二酮具有优异的致敏能力，是目前应用最广泛的镧系配合物致敏体之一。然而，引入手性基团参与共轭体系电子跃迁的困难限制了它们在镧系圆极化发光（CPL）材料中的应用。鉴于螺旋结构固有的手性，本文基于手性双-二酮酸配体组装了一对同手性四链螺旋体Eu2L4，其中间隔体上的两个点手性中心预先组织了配体(3S,4S)/(3R,4R)-3,4-二（4,4'-二（4,4,4-三氟-1,3-二氧丁基）苯氧基）-1-苄基吡咯烷，L-SS/L-RR。x射线晶体学分析表明，间隔剂中手性碳的R、R构型诱导配体的M螺旋构象，而S、S构型诱导配体的P螺旋构象。通过综合光谱表征，结合Sparkle/RM1模型的半经验几何优化，证实了预组织配体成功地控制了螺旋的同手性。此外，镜像CD和CPL光谱以及核磁共振测量证实了溶液中对映体对的形成及其非对映性。详细的光物理和热学表征研究表明，螺旋体不仅表现出强烈的圆偏振发光（CPL），垂直杆g（lum）垂直杆值达到0.10，而且具有34%的高发光量子收率。本研究有效地将螺旋酸的螺旋手性与β -二酮的优异敏化能力结合起来，为手性镧系CPL材料的合成提供了有效的策略。
beta-Diketones are one of the most widely used ligands for sensitizing the luminescence of lanthanide complexes due to their excellent sensitization abilities. However, the difficulties in introducing chiral groups to take part in the electronic transitions of conjugated systems limit their application in lanthanide circularly polarized luminescence (CPL) materials. In view of the inherent chirality of the helical structure, herein, a pair of homochiral quadruple-stranded helicates, Eu2L4, is assembled based on chiral bis-beta-diketonate ligands, wherein the two point chirality centers in the spacer preorganize the helical conformation of the ligand (3S,4S)/(3R,4R)-3,4-bis(4,4'-bis(4,4,4-trifluoro-1,3-dioxobutyl)phenoxyl)-1-benzylpyrrolidine, L-SS/L-RR. X-ray crystallographic analyses reveal that the R,R configurations of the chiral carbons in the spacer induce the M helical sense of the ligand, while the S,S configurations induce the P helical sense. Through the comprehensive spectral characterization in combination with semiempirical geometry optimization using the Sparkle/RM1 model, it is confirmed that the preorganized ligands successfully control the homochirality of the helicates. Moreover, the mirror-image CD and CPL spectra and NMR measurements confirm the formation of enantiomeric pairs and their diastereopurities in solution. Detailed photophysical and chiroptical characterization studies reveal that the helicates not only exhibit intense circularly polarized luminescence (CPL) with vertical bar g(lum)vertical bar values reaching 0.10, but also show a high luminescence quantum yield of 34%. This study effectively combines the helical chirality of the helicates with the excellent sensitization ability of the beta-diketones, providing an effective strategy for the syntheses of chiral lanthanide CPL materials.