Polzin P, V Eliani I, Ströh J, Braun M, Ruser N, Heidenreich N, Rönfeldt P, Bertram F, Näther C, Wöhlbrandt S, Suta M, Terraschke H
Institut für Anorganische Chemie, Christian-Albrechts-Universität zu Kiel, Max-Eyth-Str. 2, 24118 Kiel, Germany.
Phys Chem Chem Phys. 2018 Mar 14;20(11):7428-7437. doi: 10.1039/c7cp07142f.
In situ monitoring of the formation of emissive complexes is essential to enable the development of rational synthesis protocols, to provide accurate control over the generation of structure-related properties (such as luminescence) and to facilitate the development of new compounds. In situ luminescence analysis of coordination sensors (ILACS) utilizes the sensitivity of the spectroscopic properties of lanthanide ions to their coordination environment to detect structural changes during crystallization processes. Here, ILACS was utilized to monitor the formation of [Eu(bipy)(NO)] (bipy = 2,2'-bipyridine) during co-precipitation synthesis. Validity of the ILACS results was ensured by concomitant utilization of in situ monitoring of other reaction parameters, including in situ measurements of pH value, ionic conductivity, and infrared spectra, as well as ex situ and synchrotron-based in situ X-ray diffraction analyses. Gradual desolvation of the Eu ions and attachment of ligands were detected by an exponential increase of the intensity of the D → F (J = 0-4) transitions in the emission spectrum. Additionally, the in situ emission spectra show a decrease in the crystallization rate and an increase in the induction time in response to a reduction in the concentration of the starting solutions from 12 mM until crystallization ceased at starting reactant concentrations <6 mM. An increase to a three-fold higher concentration leads to the formation of a reaction intermediate, and its stability was determined to be highly concentration-dependent. The in situ luminescence measurements also demonstrated the existence of a ligand exchange process within the [Eu(bipy)(NO)] complex upon addition of a phen (phen = 1,10'-phenanthroline) solution and the generation of a new phen-containing emissive complex. In attempting to solve the structure of this new phen-containing complex, a different, but nevertheless previously unsynthesized complex, [Eu(phen)(NO)]bipy, was obtained, which shows characteristic Eu luminescence in the red spectral range.
原位监测发光配合物的形成对于开发合理的合成方案、精确控制与结构相关性质（如发光）的产生以及促进新化合物的开发至关重要。配位传感器的原位发光分析（ILACS）利用镧系离子光谱性质对其配位环境的敏感性来检测结晶过程中的结构变化。在此，ILACS被用于监测共沉淀合成过程中[Eu(bipy)(NO)]（bipy = 2,2'-联吡啶）的形成。通过同时利用其他反应参数的原位监测，包括pH值、离子电导率和红外光谱的原位测量，以及非原位和基于同步加速器的原位X射线衍射分析，确保了ILACS结果的有效性。通过发射光谱中D→F（J = 0 - 4）跃迁强度的指数增加检测到Eu离子的逐步去溶剂化和配体的附着。此外，原位发射光谱显示，随着起始溶液浓度从12 mM降低，结晶速率降低，诱导时间增加，直至起始反应物浓度<6 mM时结晶停止。浓度增加到三倍会导致形成反应中间体，并且确定其稳定性高度依赖于浓度。原位发光测量还证明，加入phen（phen = 1,10'-菲咯啉）溶液后，[Eu(bipy)(NO)]配合物内存在配体交换过程，并生成了一种新的含phen的发光配合物。在试图解析这种新的含phen配合物的结构时，得到了一种不同但此前未合成的配合物[Eu(phen)(NO)]bipy，它在红色光谱范围内显示出特征性的Eu发光。
