Sign reversal of a large circularly polarized luminescence signal by the twisting motion of a bidentate ligand.
Sign reversal of a large circularly polarized luminescence signal by the twisting motion of a bidentate ligand.
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DOI：
10.1002/chem.201402268
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发表时间：
2014-07
期刊：
影响因子：
--
通讯作者：
J. Yuasa;H. Ueno;T. Kawai
中科院分区：
文献类型：
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作者：
J. Yuasa;H. Ueno;T. Kawai
这项工作证明了在手性铕（III）配合物的顺反异构化过程中，基于双齿配体3,3-二（二苯基磷基）-2,2-联吡啶（BIPYPO）的铰链状扭曲运动的大圆偏振发光（CPL）信号的符号反转。x射线衍射分析表明，BIPYPO的扭转运动提供了含有三[3-（三氟甲基羟亚甲基）-(+)-樟脑酸]（D-1）或三[3-（七氟丙基羟亚甲基）-(+)-樟脑酸]（D-2）的手性Eu（III）配合物的s-顺式和s-反式几何形状。在Eu（III）离子周围的s顺式Eu（III）配合物显示出八坐标的几何形状，其中磷酰氧与Eu（III）离子之间的螯合作用迫使BIPYPO具有s顺式几何形状。相比之下，磷-氮相互作用为BIPYPO配体的s-反式几何结构提供了构象锁，诱导了准七坐标Eu（III）配合物。配位几何的差异导致了顺式和反式两种异构体CPL信号的符号变化，其中Eu（III）配合物的顺式和反式异构体在(5)D0→(7)F1跃迁过程中分别表现出正CPL信号和负CPL信号。当溶剂由[D3]乙腈变为[D6]丙酮时，s-反式d -1与s-顺式d -1的比例增加，导致CPL信号发生符号变化。配合物D-1和D-2表现出两种不同寿命的双指数衰减，表明有两种发光物质，即Eu（III）配合物的s顺式和s反式异构体。在这两种情况下，当溶剂从[D3]乙腈变为[D6]丙酮时，寿命较长的组分（τ1）的比例减小，而寿命较短的组分（τ2）的比例增加。
This work demonstrates sign reversal of large circularly polarized luminescence (CPL) signal based on the hinge-like twisting motion of a bidentate ligand, 3,3-bis(diphenylphosphoryl)-2,2-bipyridine (BIPYPO), in a cis-trans isomerization of chiral europium(III) complexes. X-ray diffraction analysis revealed that twisting motion of BIPYPO provides s-cis and s-trans geometries of a chiral Eu(III) complex containing either tris[3-(trifluoromethylhydroxymethylene)-(+)-camphorate] (D-1) or tris[3-(heptafluoropropylhydroxymethylene)-(+)-camphorate] (D-2). The s-cis Eu(III) complexes show eight-coordinate geometry around the Eu(III) ion, in which the chelate between the phosphoryl oxygen and the Eu(III) ion forces the s-cis geometry of BIPYPO. In contrast, the phosphorus-nitrogen interaction provides a conformational lock for the s-trans geometry of the BIPYPO ligand, inducing a quasi-seven-coordinate Eu(III) complex. The difference in coordination geometry causes the sign change of the CPL signals between the s-cis and s-trans isomers, whereby the s-cis and s-trans isomers of Eu(III) complexes exhibit the positive and negative CPL signals, respectively, for the (5) D0 →(7) F1 transition. The proportion of the s-trans-D-1 against s-cis-D-1 increases upon changing the solvent from [D3 ]acetonitrile to [D6 ]acetone, inducing a sign change of the CPL signals. The complexes D-1 and D-2 show a biexponential decay with two different lifetimes, suggesting two emitting species, that is, the s-cis and s-trans isomers of Eu(III) complexes. In both cases, the proportions of the longer lifetime components (τ1 ) decrease and instead the shorter lifetime components (τ2 ) increase upon changing the solvent from [D3 ]acetonitrile to [D6 ]acetone.