Ligands based on 2,2'-bipyridine and valinamide moieties induce circularly polarized luminescence in their europium complexes. Both the R and S enantiomers of the complexes were successfully obtained. Single-crystal X-ray analysis of the racemic crystal confirmed that the ligand is coordinated to the europium ion in a tetradentate fashion. The π-electronic system of the ligand is co-planar with the valinamide moiety, and acts as an efficient photoantenna to sensitize europium luminescence by UV excitation. The luminescence quantum yield (QY) of europium in the valinamide-containing complex was 44 % in acetonitrile. The glum value to evaluate the circularly polarized luminescence was relatively high at |0.13| estimated from their magnetic dipole transitions around 593 nm. For comparison, we prepared hexadentate europium complexes in the S- and R-forms derived from two bipyridine moieties linked by ethylenediamines. The determined QYs were 18 % (S) and 16 % (R), and the glum value |0.12| for the hexadentate complexes. The photophysical properties of the gadolinium complexes of the ligands were also evaluated.

中文翻译：

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镧系元素与Valinamide衍生物在溶液中的配合物光谱学研究。

基于2,2'-联吡啶和缬氨酰胺部分的配体在其complex络合物中诱导圆偏振发光。复合物的R和S对映体均成功获得。外消旋晶体的单晶X射线分析证实，配体以四齿形式与to离子配位。配体的π电子系统与缬氨酰胺部分共面，并充当有效的光天线，通过紫外线激发来敏化euro的发光。含缬氨酰胺的络合物中的in在乙腈中的发光量子产率（QY）为44％。用于评价圆偏振发光的glum值相对较高，为| 0.13 |。根据它们在593 nm附近的磁偶极跃迁估算。为了比较，我们制备了由乙二胺连接的两个联吡啶部分衍生的S和R形式的六齿euro络合物。所确定的QY为18％（S）和16％（R），glum值| 0.12 |。对于六齿配合物。还评估了配体的complex配合物的光物理性质。