β-二酮具有优异的敏化能力,是应用最广泛敏化镧系配合物发光的配体之一.但由于难以引入手性基团参与共轭体系的电子跃迁,限制了其在镧系圆偏振发光(CPL)材料中的应用.结合螺旋结构的固有手性LR/S,通过引入点手性的方式成功构筑了一对对映体纯的手性双核四股铕螺旋体(HNEt3)2(Eu2L4).结合全面的光谱表征证实了配体取代基的点手性成功诱导两个稀土 Eu3+离子采取相同的 Λ 或 Δ 构型,并形成具有单一 M 或 P 螺旋构象的螺旋体.配合物的镜像圆二色(CD)和CPL光谱进一步验证了一对光学纯对映体的形成.手性光学性质研究显示螺旋体表现出适中的发光不对称因子(|glum| =0.043)和良好的发光量子产率(QY =23%).该研究将螺旋体的手性与β-二酮的优异敏化能力有效地结合起来,为手性镧系CPL材料的合成提供了有效的策略.
Point chirality controlled homochiral self-assembly and circularly polarized luminescence in quadruple-stranded Eu2L4 helicates
β-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 incorporate the electronic transitions of conjugated systems have limited their application in circularly polarized luminescence(CPL)of lanthanide materials.On the basis of the inherent chirality of the helical structure,a pair of enantiopure dinuclear europium quadruple-stranded helicates,(HNEt3)2(Eu2L4),were assembled via a point chirality induced strategy.Comprehensive spectral characterizations demonstrated that the point chirality at the substituent of the ligand successfully induced the formation of P or M helicates with Δ or Λ configuration around two metal centers.The mirror-image CPL and CD spectra further confirmed the formation of the enantiomer pairs.Notably,the helicates exhibited excellent CPL emission with the |glum| values of 0.043 and the modest luminescence quantum yields of 23％.This study provided an effective strategy for the syntheses of chiral lanthanide CPL materials by combining the helical chirality of the helicates with the excellent sensitization ability of the β-diketones.
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