Wang Yun-Guang, Li Yu-Qian, Tang Hui-Hui, Lin Li-Rong, Ma Li-Hua
Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, P. R. China.
Department of Chemistry, College of Science and Computer Engineering, University of Houston-Clear Lake, 2700 Bay Area Blvd, Houston, Texas 77058, United States.
ACS Omega. 2018 May 21;3(5):5480-5490. doi: 10.1021/acsomega.8b00386. eCollection 2018 May 31.
Two mononuclear and one binuclear ytterbium complexes with dual near-infrared (NIR) photoluminescence and reversible trans-to-cis photoisomerization functions were synthesized and characterized. The central ytterbium(III) ion coordinates with two β-diketonate (4,4,4-trifluoro-1-phenylbutane-1,3-dionate (tfd)) ligands and one deprotonated azobenzene-containing tetradentate ligand [()-4-(phenyldiazenyl)-,-bis(pyridin-2-ylmethyl) benzohydrazide (HL), ()-4-((4-(dimethylamino)phenyl)diazenyl)-,-bis(pyridin-2-ylmethyl)benzohydrazide (HNL), or ()-4,4'-','-bis(pyridin-2-ylmethyl)benzohydrazide azobenzene (HDL)] to form a neutral ternary complex ([Yb(tfd)L], [Yb(tfd)(NL)], or [Yb(tfd)(DL)], respectively), where the ytterbium(III) ion is eight-coordinated to NO donor sets. X-ray crystallographic analysis shows that all three complexes form a trigonal dodecahedron geometry with similar -N=N- distances that are slightly longer than those of the pure azobenzene-containing ligands. The NIR luminescence properties of the Yb(III) complexes were determined at a wavelength of about 980 nm with quantum yields in the range of 0.4-0.6% in ethanol and acetonitrile solutions at room temperature, and trans-to-cis photoisomerization was determined with the quantum yields (Φ = 10) at the same level as their pure ligands. The trans-to-cis photoisomerization rates of the complexes (10 s) are slightly higher than those of the pure ligands and similar to azobenzene (10 to 10 s). From time-dependent density functional theory calculations of the energy levels of the first excited triplet states of the ligands, the energies of the lowest excited triplet states of all of the ligands are higher than the resonance level of Yb (2F, 1.2722 eV). We suggest that these azo-containing ligands may participate in energy transfer to the ytterbium ion, in addition to the main "antenna effect" ligand tfd. This is the first report of azobenzene group-functionalized ytterbium complexes with dual NIR luminescence and photoisomerization properties, indicating that azobenzene-containing lanthanide(III) complexes have potential applications as dual function materials in biological systems.
合成并表征了两种具有双近红外（NIR）光致发光和可逆反式到顺式光异构化功能的单核和一种双核镱配合物。中心镱（III）离子与两个β-二酮（4,4,4-三氟-1-苯基丁烷-1,3-二酮（tfd））配体和一个去质子化的含偶氮苯四齿配体[（）-4-（苯基重氮基）-，-双（吡啶-2-基甲基）苯甲酰肼（HL）、（）-4-（（4-（二甲基氨基）苯基）重氮基）-，-双（吡啶-2-基甲基）苯甲酰肼（HNL）或（）-4,4'-，'-双（吡啶-2-基甲基）苯甲酰肼偶氮苯（HDL）]配位形成中性三元配合物（分别为[Yb（tfd）L]、[Yb（tfd）（NL）]或[Yb（tfd）（DL）]），其中镱（III）离子与NO供体基团八配位。X射线晶体学分析表明，所有三种配合物均形成三角十二面体几何结构，其-N=N-距离相似，略长于纯含偶氮苯配体的-N=N-距离。在室温下，在乙醇和乙腈溶液中，镱（III）配合物的近红外发光特性在约980nm波长下测定，量子产率在0.4-0.6%范围内，反式到顺式光异构化的量子产率（Φ = <10>）与它们的纯配体处于同一水平。配合物的反式到顺式光异构化速率（<10>-5 s-1）略高于纯配体，与偶氮苯（<10>-5到<10>-4 s-1）相似。通过对配体第一激发三重态能级的含时密度泛函理论计算，所有配体的最低激发三重态能量均高于镱的共振能级（2F5/2，1.2722 eV）。我们认为，除了主要的“天线效应”配体tfd外，这些含偶氮配体可能参与了向镱离子的能量转移。这是关于具有双近红外发光和光异构化性质的偶氮苯基团功能化镱配合物的首次报道，表明含偶氮苯的镧系（III）配合物作为生物系统中的双功能材料具有潜在应用。
