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

为了将镧系离子的近红外发光特性应用于溶液状态下的发光传感，必须通过适当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，研究者利用稳定且高度发光的“武装环”-镧系配合物与更高的过渡金属配合物进行杂化。他成功地发展了逐步合成方法，以获得镧系过渡金属双核配合物。当Pt（II）或Re(V)配合物与镧系离子的双核配合物可以分离成晶体，并通过x射线晶体学和核磁共振分析确定了其固溶结构。在Re(V)配合物中发现了前所未有的结构，包括线性Re- o - ln键。结果表明，过渡金属配合物的能量有效地转移到能量较低的镧系离子上，镧系离子发出近红外发光。含Re(V)基团的双核配合物是一种新型的近红外发光配合物，即使在室温溶液中也能发出强烈的近红外发光。结果表明，利用这些过渡金属配合物的电荷转移吸收带，可以实现可见光到近红外光的有效转换。本研究的主要结果是：(1)合成了各种镧系过渡金属配合物，(2)两个配合物可以固定在两个配合物之间强相互作用的附近，(3)实现了可见光到近红外光的有效转换。基于这些发现，本研究将通过结合较轻的过渡金属配合物和镧系配合物来开发具有新型光磁功能的金属配合物。

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.