辛醇溶液、水溶液、固态及液-液萃取体系中TRDGA与Pr(Ⅲ)的配位研究

为加深对四烷基-3-氧杂-戊二酰胺（TRDGA）类配体与三价锕/镧离子配位的认识，利用光谱及单晶X射线衍射分析技术，分别在含水辛醇溶液、水溶液、晶体及液-液萃取体系中对比研究了脂溶性N，N′-二甲基-N，N′-二辛基-3-氧杂-戊二酰胺（DMDODGA，L）以及水溶性四甲基-3-氧杂-戊二酰胺（TMDGA，L′）与Pr(Ⅲ)的配位。光谱滴定实验结果表明，两配体在溶液中均可与Pr(Ⅲ)形成金属离子与配体比值为1∶1、1∶2及1∶3的配合物，并获得了配合物稳定常数及标准吸收光谱。配合物中金属离子与配体比值相同时，L和L′与Pr(Ⅲ)形成的每对配合物中Pr(Ⅲ)特征吸收峰的位置及形状均几乎完全相同，说明每对配合物的内配位层结构相同或相近。PrL′3(ClO4)3晶体漫反射光谱与PrL3+3及PrL′3+3标准吸收光谱的特征也相同，说明1∶3配合物均为三帽三棱柱配位构型。与加入硝酸根的光谱滴定实验相结合，通过有机相吸收光谱与已知固体/溶液配合物的漫反射/吸收光谱对比，确定了液-液萃取萃合物中，Pr(Ⅲ)至少有PrL2(NO3)(H2O)2+和PrL3+3 2种化学形态。

Complexation of Pr(Ⅲ) with Tetraalkyl Diglycolamides in Wet n-octanol,Aqueous Solution,Solid State and Solvent Extraction

To further understand the complexation of An(Ⅲ) and Ln(Ⅲ) with tetraalkyl diglycolamides (TRDGA), the complexation of Pr(Ⅲ) with water-insoluble N, N′-dimethyl-N,N′-dioctyl-diglycolamide (DMDODGA, L) and water-soluble tetramethyl-diglycolamide (TMDGA, L′) was investigated in wet n-octanol, aqueous solution, solid state and solvent extraction respectively by using spectrophotometry and X-ray crystallography. Three successive Pr(Ⅲ) complex species (1∶1, 1∶2 and 1∶3 of metal ion to ligand) for both ligands were identified in both solutions by using spectral titration method. The stability constants and standard reference absorption spectra of these complexes were acquired by spectra deconvolution. The almost identical spectra of the corresponding Pr(Ⅲ)-DMDODGA complexes in wet n-octanol and the Pr(Ⅲ)-TMDGA complexes in aqueous solution indicate each related pair shares similar coordination geometry. By using slow evaporation method, PrL3(ClO4)3 and PrL′3(ClO4)3 single crystals of sufficient quality were grown successfully from ethanol solution and aqueous solution respectively, and their structures were determined by using X-ray diffraction method. The bond lengths and stability constants of these complexes were discussed and compared with those of corresponding Am(Ⅲ)-TMDGA and Pr(Ⅲ)-TEDGA complexes. The diffuse reflectance spectra of PrL′3(ClO4)3 solid compound collected and the absorption spectra of PrL3+3 and PrL′3+3in solutions have the same characteristics, which suggests that Pr(Ⅲ) in these 1∶3 complexes shares a same inner coordination sphere. And the X-ray diffraction analysis results show that Pr(Ⅲ) ions in these two 1∶3 crystals are both coordinated with three tridentate ligands (DMDODGA or TMDGA) to form a geometry of distorted tricapped trigonal prism (TCTP). Using varying concentrations of DMDODGA in 40% n-octonol-60% kerosene (V/V) as initial organic phases and 1.0 mol/L HNO3 0.05 mol/L Pr(NO3)3 as initial aqueous phases, a set of samples of the extracted Pr(Ⅲ) complexes were prepared and their absorption spectra were collected. The factor analyses of these spectra show that there were no less than two extracted Pr(Ⅲ) species existing in these samples. To probe into the role of nitrate played in the extraction process, using the mixture of Pr(Ⅲ) and DMDODGA in wet n-octanol as the starting solution, a nitrate involved spectral titration experiment was carried out. Unlike the way it does in aqueous solutions, the result shows that the nitrite may bind to metal center of the Pr(Ⅲ)-DMDODGA complexes directly in wet n-octanol. Combining all of the experimental results, the extracted Pr(Ⅲ) complex species were identified as PrL2(NO3)(H2O)2+ and PrL3+3 for the first time.