Bhattacharyya Arunasis, Ansari Seraj A, Gadly Trilochan, Ghosh Sunil K, Mohapatra Manoj, Mohapatra P K
Radiochemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai-400085, India.
Dalton Trans. 2015 Apr 7;44(13):6193-201. doi: 10.1039/c5dt00149h.
Mutual separation of trivalent actinide (An(3+)) and lanthanide (Ln(3+)) using several soft (N) donor ligands (bis(5,6-dialkyl-1,2,4-triazinyl)pyridine (R-BTP)) is attempted for the first time in room temperature ionic liquid (RTIL) medium. The results indicate a spectacular enhancement in the selectivity as compared to that in molecular diluents with a separation factor (S.F.) of >3000 for Am(3+) over Eu(3+) using the methyl derivative (Me-BTP) in RTIL medium using [C(n)mim]·[NTf2] as the diluents (where n = 2, 3, 4, 6 or 8). Such a high S.F. value has never been reported before with any of the R-BTP derivatives in molecular diluents. An opposite trend in the distribution ratio values of both Am(3+) and Eu(3+) with the increasing size of the alkyl (R) group is observed in RTIL medium when compared with that in molecular diluents. The differences in the extraction behaviour of R-BTPs in RTILs vis-à-vis molecular diluents are explained on the basis of the difference in the nature of complexes extracted in these two distinctly different media as supported by the time resolved fluorescence (TRFS) study. An unusually high extractability and selectivity for Am(3+) over Eu(3+) with Me-BTP was attributed to the formation of a 1 : 4 complex for Am(3+), which was never reported earlier with any of the R-BTP derivatives in molecular diluents. DFT studies indicated higher metal 'd' and 'f' orbital participation (covalence) in the bonding with R-BTP in the case of Am(3+) complexes as compared to that in the case of Eu(3+) complexes, which resulted in the selectivity of these classes of ligands. The observed results may have a great significance in the radioactive waste management involving the partitioning and transmutation strategy.
首次尝试在室温离子液体（RTIL）介质中使用几种软（N）供体配体（双（5,6-二烷基-1,2,4-三嗪基）吡啶（R-BTP））实现三价锕系元素（An(3+)）和镧系元素（Ln(3+)）的相互分离。结果表明，与分子稀释剂相比，选择性有显著提高，在以[C(n)mim]·[NTf2]为稀释剂的RTIL介质中（其中n = 2、3、4、6或8），使用甲基衍生物（Me-BTP）时，Am(3+)对Eu(3+)的分离因子（S.F.）>3000。在分子稀释剂中，从未有任何R-BTP衍生物报道过如此高的S.F.值。与分子稀释剂相比，在RTIL介质中观察到Am(3+)和Eu(3+)的分配比值随烷基（R）基团尺寸增大呈现相反趋势。基于时间分辨荧光（TRFS）研究的支持，根据在这两种截然不同的介质中萃取的络合物性质差异，解释了R-BTPs在RTILs和分子稀释剂中的萃取行为差异。Me-BTP对Am(3+)相对于Eu(3+)具有异常高的萃取率和选择性，这归因于形成了Am(3+)的1∶4络合物，在分子稀释剂中，从未有任何R-BTP衍生物报道过这种情况。密度泛函理论（DFT）研究表明，与Eu(3+)络合物相比，在Am(3+)络合物中，金属“d”和“f”轨道在与R-BTP键合中的参与度（共价性）更高，这导致了这类配体的选择性。观察到的结果在涉及分离和嬗变策略的放射性废物管理中可能具有重大意义。
