配体结构对铀配位性能影响的理论研究

匙芳廷，文　君，熊　洁，胡　胜，魏贵林，易发成

1.西南科技大学，核废物与环境安全国防重点学科实验室，四川 绵阳　621010；2.中国工程物理研究院 核物理与化学研究所，四川 绵阳　621900



配体结构对铀配位性能影响的理论研究

匙芳廷1,2，文君2,*，熊洁2，胡胜2，魏贵林1，易发成1

1.西南科技大学，核废物与环境安全国防重点学科实验室，四川 绵阳621010；2.中国工程物理研究院 核物理与化学研究所，四川 绵阳621900

海水提铀；密度泛函；配体结构设计；分子轨道

1　计算方法

2　结果与讨论

2.1几何结构优化

(1)

图2　配体的构型Fig.2　Geometric configuration of ligands

2.2热力学参数、配位稳定常数

配离子(配原子)的配位稳定常数用K来表示，配位稳定常数越大，形成配离子(配原子)越稳定。配合物的形成过程可以简单的理想化为反应式(2)。

(2)

通过计算配位过程中焓变(ΔH)、熵变(ΔS)、热力学能变(ΔU)、吉布斯自由能(ΔG)和配位稳定常数(lgK)，进一步比较了配合物的稳定性，上述参数列入表3。ΔH、ΔG和lgK可以用公式(3)—(5)求得。

(3)

(4)

(5)

表3配合物[UO2(Ax)(H2O)3]+的热力学参数与配位稳定常数

Table 3Thermodynamic parameters and coordination stability constants of uranyl ligand complexes([UO2(Ax)(H2O)3]+)

配体类型气态ΔS/(cal·mol-1·K-1)ΔU/(kcal·mol-1)ΔH/(kcal·mol-1)ΔG/(kcal·mol-1)lgKk2-A1-135.8927.969-245.219-204.72335.897k2-A2-126.6658.553-458.861-421.11573.840k2-A3-127.4028.952-469.399-431.43375.649k2-A4-140.0587.839-448.537-406.80071.330η2-A4-125.2969.240-466.554-429.21675.260配体类型水溶液ΔS/(cal·mol-1·K-1)ΔU/(kcal·mol-1)ΔH/(kcal·mol-1)ΔG/(kcal·mol-1)lgKk2-A1-130.117.485-82.063-43.2907.590k2-A2-129.6976.779-126.612-87.96215.424k2-A3-127.7456.754-137.049-98.98117.356k2-A4-123.8668.323-119.726-82.81414.521η2-A4-120.9558.395-136.974-100.92917.697

2.3分子轨道

(a)——[UO2(η2-A4)(H2O)3]+，(b)——[UO2(k2-A1)(H2O)3]+，(c)——[UO2(k2-A2)(H2O)3]+，(d)——[UO2(k2-A3)(H2O)3]+，(e)——[UO2(k2-A4)(H2O)3]+ OLP：氧原子的孤对电子；NLP：氮原子的孤对电子；π(N-O)：N-O形成的π键 图3　配合物[UO2(Ax)(H2O)3]+典型的分子轨道(MO)Fig.3　Representative diagram of molecular orbital of [UO2(Ax)(H2O)3]+ complexes

[UO2(Ax)(H2O)3]+轨道能量/eV分子轨道(MO)分子轨道主要组成[UO2(η2-A4)(H2O)3]+-8.558OLP,π(N-O)1δuOpz,Npz,Ufz-10.140π(N-O)3σuOpz,Npz,Uf3z-10.192OLP,NLP1φuOpx,Opy,Ufx-11.165OLP3σuNpz,Opz,Cpz,Uf3z-11.319π(N-O)2πuOpx,Opy,Npx,Uf2zx,Uf2zy-11.6162πuOpx,Opy,Uf2zx,Uf2zy-13.108π(N-O)1πgOpz,Cpz,Npz,Ud3z[UO2(k2-A1)(H2O)3]+-15.460OLP2σgOpx,Npx,Ufx,Uf2zx-17.012OLP1σgOpz,Udxz[UO2(k2-A2)(H2O)3]+-10.994N-OLPσgUf3z,Opz-12.047C=OLPσgOpx,Opy,Uf2zx,Uf2zy-12.049N-OLPσgOpx,Opy,Opz,Uf2zx,Uf2zy-12.356N-OLPσgOpz,Opx,Opy,Ud2z,Uf2zx-12.629C=OLPσgOpx,Opy,Opz,Udyz,Udxz[UO2(k2-A3)(H2O)3]+-10.651NLPσgUf3z,Npz-10.798OLPσgNpz,Uf3z,Ufz,Uf2zy-11.798OLPσgOpx,Opy,Uf2zy,Uf2zx-11.853NLPσgNpx,Uf2zx[UO2(k2-A4)(H2O)3]+-10.840OLPσgUf3z,Opz-11.934NLPσgNpy,Uf2zy-13.100π(N-O)1πgUdzy,Opy,Npz

由图3(e)可知，与[UO2(η2-A4)(H2O)3]+相比，π电子云没有有效地与U轨道重叠，只有Opz轨道重叠形成σ键，同时N连有两个H因此电子云密度低于[UO2(k2-A3)(H2O)3]+中A3的N的电子云密度，综合两个因素，k2-A4与U配位能力低于η2-A4和k2-A3。

通过分析配合物典型的成键分子轨道，得到配位原子O或N主要成键轨道为p轨道，中心原子主要成键轨道为d、f轨道；当配体螯合构型配位时，主要形成σ键，当配位原子的邻位是给电子基团时有利于σ键的形成；配体π电子云重叠成键时，π键周围有给电子时有利于配位；因此容易与U配位的是k2-A3和η2-A4，分子轨道分析与水溶液条件下配位常数lgK计算结果一致。

3　结　论

(3) 通过热力学参数、分子轨道分析，当配体螯合构型(k2)配位时，主要形成σ键，当配位原子的邻位是给电子基团时有利于σ键的形成；当配体π电子云重叠成键时，π键周围有给电子基并能形成共轭时有利于配位；因此容易与U配位的是k2-A3和η2-A4，与水溶液条件下配位常数lgK计算结果一致。

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Density Functional Theory Study on Selective Complexation of Uranyl(Ⅵ) With Ligands Possessing Different Configuration

CHI Fang-ting1,2, WEN Jun2,*, XIONG Jie2, HU Sheng2, WEI Gui-lin1, YI Fa-cheng1

1.Fundamental Science on Nuclear Wastes and Environmental Safety Laboratory,Southwest University of Science and Technology, Mianyang 621010, China；2.Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, China

recovery uranium from seawater; density functional theory; designation of ligand structure; molecular orbital

2015-09-11；

2015-11-19

国家自然科学基金项目(21401152)；西南科技大学博士研究基金项目(13zx7130)；西南科技大学核废物与环境安全国防重点学科实验室预研项目(15yyhk08)；西南科技大学核废物与环境安全国防重点学科实验室团队项目(14tdhk01)

匙芳廷(1982—)，女，山东聊城人，博士，副教授，从事海水提铀吸附剂研究与放射性废物处理研究

*通信联系人：文君(1985—)，男，四川乐山人，副研究员，放射化学专业，E-mail: junwen@caep.cn

TL941

A

0253-9950(2016)04-0238-09

10.7538/hhx.2016.38.04.0238