Chen Xiuting, Xiong Zhixin, Gong Yu
Department of Radiochemistry, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China.
School of Nuclear Science and Technology, University of Chinese Academy of Sciences, Beijing 100049, China.
Inorg Chem. 2020 Oct 5;59(19):14486-14492. doi: 10.1021/acs.inorgchem.0c02285. Epub 2020 Sep 3.
Electrospray ionization of LnCl and tetramethylpyridine-2,6-dicarboxamide (TMPDA) mixtures in methanol generated abundant tripositively charged Ln(TMPDA) ions with an unprecedented 1:2 stoichiometry in the gas phase. Different from the very common 1:3 Ln(L) (L = TMGA, tetramethyl glutaramide; TMOGA, tetramethyl-3-oxaglutaramide; TMTDA, tetramethyl-3-thiodiglycolamide) complexes, Ln is coordinated by four O and two N atoms from two perpendicular TMPDA ligands based on the DFT calculations. The observation of 1:2 Ln(TMPDA) in the gas phase is due to the desolvation of Ln(TMPDA)(MeOH) that is predominant in the methanol solution of LnCl and TMPDA according to the extended X-ray absorption fine structure analysis, and the 1:3 Ln(TMOGA) and Ln(TMGA) complexes observed in the gas phase also parallel the speciation in relevant solutions. Such a difference in solution speciation is most likely a result of the unfavorable steric effect caused by the pyridine ring of TMPDA.
在甲醇中，对氯化镧（LnCl）和2,6 - 二甲基吡啶二甲酰胺（TMPDA）的混合物进行电喷雾电离，在气相中产生了大量具有前所未有的1:2化学计量比的三价正电荷Ln(TMPDA)离子。与非常常见的1:3 Ln(L)（L = TMGA，四甲基戊二酰胺；TMOGA，四甲基 - 3 - 氧代戊二酰胺；TMTDA，四甲基 - 3 - 硫代二甘醇酰胺）配合物不同，基于密度泛函理论计算，Ln由来自两个垂直的TMPDA配体的四个O原子和两个N原子配位。根据扩展X射线吸收精细结构分析，在气相中观察到1:2的Ln(TMPDA)是由于Ln(TMPDA)(MeOH)在LnCl和TMPDA的甲醇溶液中占主导地位的去溶剂化作用，并且在气相中观察到的1:3 Ln(TMOGA)和Ln(TMGA)配合物也与相关溶液中的物种形成情况相似。溶液物种形成的这种差异很可能是由TMPDA的吡啶环引起的不利空间效应导致的。
