School of Chemistry , The University of Birmingham , Edgbaston B15 2TT , United Kingdom.
Department of Chemistry , Southern University of Science and Technology , Shenzhen 518055 , China.
Inorg Chem. 2019 Oct 7;58(19):13268-13275. doi: 10.1021/acs.inorgchem.9b02090. Epub 2019 Sep 25.
The design of coordination sites around lanthanide ions has a strong impact on the sensitization of their luminescent signal. An imidodiphosphonate anionic binding site is attractive as it can be functionalized with "remote" sensitizer units, such as phenoxy moieties, namely, HtpOp, accompanied by an increased distance of the lanthanide from the ligand high-energy stretching vibrations which quench the luminescence signal, hence providing flexible shielding of the lanthanide. We report the formation and isolation of Ln(tpOp) complexes where Ln = Er, Gd, Tb, Dy, Eu, and Yb and the Y(tpOp) diamagnetic analogue. The complexes are formed from reaction of KtpOp and the corresponding LnCl·6HO salt either by titration and in situ formation or by mixing and isolation. All complexes are seven-coordinated by three tpOp ligand plus one ethanol molecule, except for Yb(tpOp) which has no solvent coordinated. Phosphorus NMR shows characteristic shifts to support the coordination of the lanthanide complexes. The complexes display visible and near-infrared luminescence with long lifetimes even for the near-infrared complexes which range from 3.3 μs for Nd(tpOp) to 20 μs for Yb(tpOp). The ligand shows more efficient sensitization than the imidodiphosphinate analogues for all lanthanide complexes with a notable quantum yield of the Tb(tpOp) complex at 45%. We attribute this to the properties of the remote sensitizer unit and its positioning further away from the lanthanide, eliminating quenching of high energy C-H vibrations from the ligand shell. Calculations of the ligand shielding support the photophysical properties of the complexes. These results suggest that these binding sites are promising in the further development of the lanthanide complexes in optoelectronic devices for telecommunications and new light emitting materials.
镧系离子配位位点的设计对其发光信号的敏化有很大的影响。亚氨基二膦酸阴离子结合位点很有吸引力，因为它可以用“远程”敏化剂单元（例如苯氧基部分）进行功能化，即 HtpOp，并伴有增加的镧系元素与配体高能伸缩振动的距离，从而猝灭发光信号，从而提供镧系元素的灵活屏蔽。我们报告了 Ln(tpOp)配合物的形成和分离，其中 Ln = Er、Gd、Tb、Dy、Eu 和 Yb 以及 Y(tpOp)反磁性类似物。这些配合物是通过 KtpOp 和相应的 LnCl·6HO 盐反应形成的，要么通过滴定和原位形成，要么通过混合和分离。所有配合物均由三个 tpOp 配体加一个乙醇分子七配位，除了 Yb(tpOp)，它没有溶剂配位。磷 NMR 显示出特征位移以支持镧系元素配合物的配位。这些配合物显示出可见和近红外发光，寿命长，即使对于近红外配合物，其范围从 Nd(tpOp)的 3.3 μs 到 Yb(tpOp)的 20 μs。与所有镧系元素配合物相比，该配体显示出更高的敏化效率，其中 Tb(tpOp)配合物的量子产率为 45%。我们将这归因于远程敏化剂单元的性质及其与镧系元素的更远距离定位，从而消除了配体壳层中高能 C-H 振动的猝灭。配体屏蔽的计算支持了配合物的光物理性质。这些结果表明，这些结合位点在进一步开发用于电信和新型发光材料的光电设备中的镧系元素配合物方面具有广阔的前景。
