氮氧配位原子分子内协同效应对锕系/镧系元素选择性的影响机理研究

Along with the development of fast neutron reactor, the GANEX concept, addressing the simultaneous partitioning of all transuranium (TRU) elements in a homogeneously separation cycle, becomes the new trend of the researches on the spent fuel reprocessing. Funding the scientific research on the GANEX concept is very important for us to develop the closed fuel cycle based on our fast neutron reactors in the future. The amide derivatives of the quadridentate carboxylic ligands bearing heterocyclic N-donors are of the most potential.It is still unknown for the intra-molecular synergistic effects of ligand, such as the ratio of N and O donors, donor arrangement, and preorgnization, on its selective complexation with actinides over lanthanides. In the present project,the carboxylic ligands with various aromatic N-donors were designed. Their complexation with actinides in solid and aqueous phases would be studied seriously by experiments and calculations, investigating the effects of the intra-ligand synerstic effects of donors on the coordination property of ligands, and exploring the chemical mechanics of the intra-ligand synergism of donors on the acitinide selcetivity of ligands over lantanides. This project is devoted to deepen the theoretial underatanding of the coordination chemistry of actinides, and pays practical guidance for developing efficient extractants for the GANEX concept.

随着快堆技术日益成熟，以单循环分离回收超铀元素的GANEX流程概念成为后处理技术研究的方向。开展GANEX流程萃取剂设计基础研究对推动我国以快堆为基础的闭合燃料循环研究有重要作用。含芳香氮的氮氧混合配体是极具潜力的GANEX流程萃取剂。配位原子的分子内协同效应对配体的络合性能和锕系元素选择性的影响显著，但这种配体骨架结构对配体性能影响的规律和机理还不清楚。本项目以联吡啶和邻菲洛啉为基本结构单元，设计一些列具有不同氮氧比例、配位原子排列方式和预组织性的氮氧混合配体骨架化合物，分别从固体络合物结构、溶液络合反应热力学和配位方式、量子化学计算等多角度，研究配位原子分子内协同效应对配体与锕系元素络合性能的影响规律，揭示配位原子分子内协同效应对5f电子与4f电子配位键强度影响机理。研究成果对深入理解锕系元素配位化学性质特性有重要理论意义，对新型GANEX流程萃取剂设计和结构优化有重要指导作用。

本项目研究芳香性氮氧混合配体与镧系和锕系元素络合物稳定性与配体碱性、配位原子预组织性的关系及其热力学根源和晶体结构特征。通过大量溶液化学热力学性质测量和络合物晶体结构分析、以及适当的量子化学计算，论证了镧系/锕系元素与氮氧混合配体配位的离子键本质。以相同配位原子预组织性的不同碱性的二齿芳香性氮氧配体比较，讨论了配体碱性强度与络合物稳定性和M-N配位键长度的正相关关系；着重以不同配位原子预组织性四齿芳香性氮氧混合配体的镧系/锕系元素络合物比较，证实提高配体预组织性对增强其镧系/锕系元素络合物稳定性的积极作用，其热力学根源在于熵有利，其晶体结构表现为配位结构张力降低。设计了一种新的具有良好配位原子预组织性的三齿芳香性氮氧混合配体，通过配体碱性和预组织性控制，获得良好的Am(III)/Eu(III)萃取分离能力和优良Am(III)/Cm(III)萃取分离能力。本项目研究结果有助于深入理解镧系/锕系元素配位化学性质及其与配体结构的关系、及其热力学推动力和配位结构特征；对镧系/锕系元素分离配体设计和结构优化具有指导作用和重要参考价值。