Eliseeva Svetlana V, Kotova Oxana V, Gumy Frédéric, Semenov Sergey N, Kessler Vadim G, Lepnev Leonid S, Bünzli Jean-Claude G, Kuzmina Natalia P
Department of Chemistry, Department of Materials Sciences, Lomonosov Moscow State University, Leninskie Gory 1-3, 119991 Moscow, Russia. eliseeva@ inorg.chem.msu.ru
J Phys Chem A. 2008 Apr 24;112(16):3614-26. doi: 10.1021/jp711305u. Epub 2008 Mar 22.
Two types of dimeric complexes [Ln2(hfa)6(mu2-O(CH2)2NHMe2)2] and [Ln(thd)2(mu2,eta2-O(CH2)2NMe2)]2 (Ln = YIII, EuIII, GdIII, TbIII, TmIII, LuIII; hfa- = hexafluoroacetylacetonato, thd- = dipivaloylmethanato) are obtained by reacting [Ln(hfa)3(H2O)2] and [Ln(thd)3], respectively, with N,N-dimethylaminoethanol in toluene and are fully characterized. X-ray single crystal analysis performed for the TbIII compounds confirms their dimeric structure. The coordination mode of N,N-dimethylaminoethanol depends on the nature of the beta-diketonate. In [Tb2(hfa)6(mu2-O(CH2)2NHMe2)2], eight-coordinate TbIII ions adopt distorted square antiprismatic coordination environments and are O-bridged by two zwitterionic N,N-dimethylaminoethanol ligands with a Tb1...Tb2 separation of 3.684(1) A. In [Tb(thd)2(mu2,eta2-O(CH2)2NMe2)]2, the N,N-dimethylaminoethanol acts as chelating-bridging O,N-donor anion and the TbIII ions are seven-coordinate; the Tb1...Tb1A separation amounts to 3.735(2) A within centrosymmetric dimers. The dimeric complexes are thermally stable up to 180 degrees C, as shown by thermogravimetric analysis, and their volatility is sufficient for quantitative sublimation under reduced pressure. The EuIII and TbIII dimers display metal-centered luminescence, particularly [Eu2(hfa)6(O(CH2)2NHMe2)2] (quantum yield Q(L)Ln = 58%) and [Tb(thd)2(O(CH2)2NMe2)]2 (32%). Consideration of energy migration paths within the dimers, based on the study of both pure and EuIII- or TbIII-doped (0.01-0.1 mol %) LuIII analogues, leads to the conclusion that both the beta-diketone and N,N-dimethylaminoethanol ligands contribute significantly to the sensitization process of the EuIII luminescence. The ancillary ligand increases considerably the luminescence of [Eu2(hfa)6(O(CH2)2NHMe2)2], compared to [Ln(hfa)3(H2O)2], through the formation of intra-ligand states while it is detrimental to TbIII luminescence in both beta-diketonates. Thin films of the most luminescent compound [Eu2(hfa)6(O(CH2)2NHMe2)2] obtained by vacuum sublimation display photophysical properties analogous to those of the solid-state sample, thus opening perspectives for applications in electroluminescent devices.
通过分别使[Ln(hfa)3(H2O)2]和[Ln(thd)3]与N,N - 二甲基氨基乙醇在甲苯中反应，得到了两种二聚配合物[Ln2(hfa)6(μ2 - O(CH2)2NHMe2)2]和[Ln(thd)2(μ2,η2 - O(CH2)2NMe2)]2（Ln = YIII、EuIII、GdIII、TbIII、TmIII、LuIII；hfa- = 六氟乙酰丙酮基，thd- = 二新戊酰甲烷基），并对其进行了全面表征。对TbIII化合物进行的X射线单晶分析证实了它们的二聚结构。N,N - 二甲基氨基乙醇的配位模式取决于β - 二酮酸酯的性质。在[Tb2(hfa)6(μ2 - O(CH2)2NHMe2)2]中，八配位的TbIII离子采用扭曲方形反棱柱配位环境，并由两个两性离子N,N - 二甲基氨基乙醇配体通过O桥连，Tb1...Tb2间距为3.684(1) Å。在[Tb(thd)2(μ,η - O(CH2)2NMe2)]2中，N,N - 二甲基氨基乙醇作为螯合 - 桥连的O,N供体阴离子，TbIII离子为七配位；在中心对称二聚体中，Tb1...Tb1A间距为约3.735(2) Å。热重分析表明，二聚配合物在高达180℃时热稳定，其挥发性足以在减压下进行定量升华。EuIII和TbIII二聚体表现出以金属为中心的发光，特别是[Eu2(hfa)6(O(CH2)2NHMe2)2]（量子产率Q(L)Ln = 58%）和[Tb(thd)2(O(CH2)2NMe2)]2（32%）。基于对纯的以及EuIII或TbIII掺杂（0.01 - 0.1 mol%）的LuIII类似物的研究，对二聚体内的能量迁移路径进行考量后得出结论，β - 二酮和N,N - 二甲基氨基乙醇配体对EuIII发光的敏化过程都有显著贡献。与[Ln(hfa)3(H2O)2]相比，辅助配体通过形成配体内态极大地增强了[Eu2(hfa)6(O(CH2)2NHMe2)2]的发光，而在两种β - 二酮酸酯中它对TbIII发光都有不利影响。通过真空升华得到的最具发光性的化合物[Eu2(hfa)6(O(CH2)2NHMe2)2]薄膜表现出与固态样品类似的光物理性质，从而为电致发光器件的应用开辟了前景。
