Construction of Lanthanide Luminescence Sensing Systems using Near-infrared Spectral Region

为了将稀土离子的近红外发光性质应用于溶液状态下的发光传感，需要通过选择合适的配体结构来提高发光量子产率和抑制发光猝灭过程。为此，研究人员利用稳定和高发光的“武装环烯”稀土络合物与更高过渡金属络合物进行杂交。他成功地开发了逐步合成程序来获得镧系元素-过渡金属双核配合物。当使用铂(II)或稀土(V)配合物时，它们与稀土离子的双核配合物可以分离出来形成晶体，并通过X-射线结晶学和核磁共振分析确定了它们的固体和溶液结构。在Re(V)配合物中发现了包括线形Re-O-Ln键在内的前所未有的结构，从而有效地实现了过渡金属络合物向能量较低的稀土离子的能量转移，产生了来自稀土离子的近红外发光。含Re(V)的双核配合物在室温溶液中也能发出强烈的近红外发光，是一种新型的近红外发光配合物。结果表明，利用这些过渡金属络合物的电荷转移吸收带可以有效地实现可见光到近红外光的转换。本研究的主要结果是：(1)合成了各种稀土过渡金属配合物；(2)两种配合物可以固定在相互作用较强的附近；(3)实现了从可见光到近红外光的高效转换。基于这些发现，本研究将通过将较轻的过渡金属络合物与稀土络合物结合起来，开发具有新的光磁功能的金属络合物。

To apply the near-infrared luminescent properties of lanthanide ions for luminescence sensing in the solution states, enhancements of luminescence quantum yields and suppression of the luminescence quenching processes by using proper ligand architecture are necessary. For this purpose, the investigator utilized stable and highly luminescent "armed cyclen"-lanthanide complexes for hybridization with higher transition metal complexes. He has succeeded to develop stepwise synthetic procedures to obtain lanthanide-transition metal dinuclear complexes. When Pt(II) or Re(V) complexes were employed, their dinuclear complexes with lanthanide ions could be isolated as crystals, and their solid and solution structures were determined by X-ray crystallography and NMR analysis. Unprecedented structures including linear Re-O-Ln bonds were found in the Re(V) complexes.As the results, the energy transfer from the transition metal complexes to the energetically lower-lying lanthanide ions efficiently took place, giving near-infrared luminescence from the lanthanide ions. The dinuclear complexes including Re(V) moieties, which gave intense near-infrared luminescence even in solution at room temperature, were found to be novel near-infrared luminescent complexes. It was demonstrated that effective visible to near-infrared light conversion was possible by using the charge-transfer absorption bands of these transition metal complexes. The main results of this research are (1) that various lanthanide-transition metal complexes have been synthesized, (2) that the two complexes could be fixed in a proximity where strong interaction between two complexes are possible, and (3) that efficient visible to near-infrared light conversion was achieved. Based on these findings, the present research will lead to the development of metal complexes with novel photo-magnetic functions by combiing lighter transition metal complexes and lanthanide complexes.