Département de Chimie Moléculaire, Univ. Grenoble Alpes, UMR-5250 CNRS UGA, CS 40700, 38058 Grenoble Cedex 9, France.
Univ. Grenoble Alpes, CNRS, CEA, INAC-SyMMES, 38000 Grenoble, France.
Dalton Trans. 2018 Aug 21;47(31):10742-10751. doi: 10.1039/c8dt01165f. Epub 2018 Jun 28.
The tripodal ligand TREN-(3,5-di-tert-butylsalicylidene) (HL) was synthesized and its tris(phenolato) lanthanide complexes L-Ln (Ln = Nd, Eu, Tb, Gd, Er, Yb and Lu) were prepared. The X-Ray crystal structures confirm that each metal ion resides in a similar monocapped octahedral geometry, excluding water molecules from the coordination sphere. The coordination bond distances are in agreement with the lanthanide contraction, with Ln-O bond lengths in the range 2.139-2.216 Å. The complexes show three reversible monoelectronic oxidation waves, which are assigned to the successive oxidation of the phenolate moieties to phenoxyl radicals. The L-Nd complex is the easiest to oxidize, with E = 0.11, E = 0.21 and E = 0.34 V vs. Fc/Fc, due to the larger size of the lanthanide ion. The ΔE value (ΔE = E-E) is correlated to the lanthanide radius, with values of 0.10 V for L-Nd and 0.22 V for L-Lu. The monoradical species were persistent in solution, allowing for their characterisation. All exhibit a distinct absorption band at around 445 nm due to the phenoxyl π-π* transitions. The EPR spectrum of L-Lu consists of a single resonance at g = 1.999, confirming the radical nature of the oxidized product. Most of the other complexes (L-Gd, L-Er, L-Yb) show a quenching of the Ln-based resonances upon oxidation, indicative of magnetic interactions between the metal and the radical spins. The L-Ln (L = Nd, Er, Yb) complexes exhibit a metal-based luminescence upon excitation of the ligand. A significant quenching of the luminescence was observed upon radical formation: 92%, 83% and 79% respectively for L-Nd, L-Er and L-Yb.
三齿配体 TREN-（3,5-二叔丁基水杨醛）（HL）被合成，并制备了其三（苯酚）镧系元素配合物 L-Ln（Ln = Nd、Eu、Tb、Gd、Er、Yb 和 Lu）。X 射线晶体结构证实，每个金属离子都位于类似的单帽八面体几何结构中，配位球中不包含水分子。配位键距离与镧系元素收缩一致，Ln-O 键长在 2.139-2.216 Å 范围内。这些配合物显示出三个可逆的单电子氧化波，这归因于酚氧基部分的连续氧化生成酚氧自由基。L-Nd 配合物最容易氧化，E = 0.11、E = 0.21 和 E = 0.34 V 相对于 Fc/Fc，这是由于镧系元素离子的尺寸较大。ΔE 值（ΔE = E-E）与镧系元素半径相关，对于 L-Nd 为 0.10 V，对于 L-Lu 为 0.22 V。单自由基物种在溶液中持久存在，允许对其进行表征。所有配合物在大约 445 nm 处都显示出明显的吸收带，这归因于酚氧自由基的 π-π*跃迁。L-Lu 的 EPR 谱由一个单共振组成，g = 1.999，证实了氧化产物的自由基性质。大多数其他配合物（L-Gd、L-Er、L-Yb）在氧化时显示出镧系元素共振的猝灭，表明金属和自由基自旋之间存在磁相互作用。L-Ln（L = Nd、Er、Yb）配合物在配体激发时表现出基于金属的发光。在自由基形成时观察到发光的显著猝灭：对于 L-Nd、L-Er 和 L-Yb，分别为 92%、83%和 79%。
