匙芳廷，文　君，熊　潔，胡　勝，魏貴林，易發(fā)成

1.西南科技大學(xué)，核廢物與環(huán)境安全國防重點(diǎn)學(xué)科實(shí)驗(yàn)室，四川 綿陽　621010；2.中國工程物理研究院 核物理與化學(xué)研究所，四川 綿陽　621900

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配體結(jié)構(gòu)對(duì)鈾配位性能影響的理論研究

匙芳廷1,2，文君2,*，熊潔2，胡勝2，魏貴林1，易發(fā)成1

1.西南科技大學(xué)，核廢物與環(huán)境安全國防重點(diǎn)學(xué)科實(shí)驗(yàn)室，四川 綿陽621010；2.中國工程物理研究院 核物理與化學(xué)研究所，四川 綿陽621900

海水提鈾；密度泛函；配體結(jié)構(gòu)設(shè)計(jì)；分子軌道

1　計(jì)算方法

2　結(jié)果與討論

2.1幾何結(jié)構(gòu)優(yōu)化

(1)

圖2　配體的構(gòu)型Fig.2　Geometric configuration of ligands

2.2熱力學(xué)參數(shù)、配位穩(wěn)定常數(shù)

配離子(配原子)的配位穩(wěn)定常數(shù)用K來表示，配位穩(wěn)定常數(shù)越大，形成配離子(配原子)越穩(wěn)定。配合物的形成過程可以簡(jiǎn)單的理想化為反應(yīng)式(2)。

(2)

通過計(jì)算配位過程中焓變(ΔH)、熵變(ΔS)、熱力學(xué)能變(ΔU)、吉布斯自由能(ΔG)和配位穩(wěn)定常數(shù)(lgK)，進(jìn)一步比較了配合物的穩(wěn)定性，上述參數(shù)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]+的熱力學(xué)參數(shù)與配位穩(wěn)定常數(shù)

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

配體類型氣態(tài)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配體類型水溶液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分子軌道

(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：氧原子的孤對(duì)電子；NLP：氮原子的孤對(duì)電子；π(N-O)：N-O形成的π鍵 圖3　配合物[UO2(Ax)(H2O)3]+典型的分子軌道(MO)Fig.3　Representative diagram of molecular orbital of [UO2(Ax)(H2O)3]+ complexes

[UO2(Ax)(H2O)3]+軌道能量/eV分子軌道(MO)分子軌道主要組成[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)1πg(shù)Opz,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)1πg(shù)Udzy,Opy,Npz

由圖3(e)可知，與[UO2(η2-A4)(H2O)3]+相比，π電子云沒有有效地與U軌道重疊，只有Opz軌道重疊形成σ鍵，同時(shí)N連有兩個(gè)H因此電子云密度低于[UO2(k2-A3)(H2O)3]+中A3的N的電子云密度，綜合兩個(gè)因素，k2-A4與U配位能力低于η2-A4和k2-A3。

通過分析配合物典型的成鍵分子軌道，得到配位原子O或N主要成鍵軌道為p軌道，中心原子主要成鍵軌道為d、f軌道；當(dāng)配體螯合構(gòu)型配位時(shí)，主要形成σ鍵，當(dāng)配位原子的鄰位是給電子基團(tuán)時(shí)有利于σ鍵的形成；配體π電子云重疊成鍵時(shí)，π鍵周圍有給電子時(shí)有利于配位；因此容易與U配位的是k2-A3和η2-A4，分子軌道分析與水溶液條件下配位常數(shù)lgK計(jì)算結(jié)果一致。

3　結(jié)　論

(3) 通過熱力學(xué)參數(shù)、分子軌道分析，當(dāng)配體螯合構(gòu)型(k2)配位時(shí)，主要形成σ鍵，當(dāng)配位原子的鄰位是給電子基團(tuán)時(shí)有利于σ鍵的形成；當(dāng)配體π電子云重疊成鍵時(shí)，π鍵周圍有給電子基并能形成共軛時(shí)有利于配位；因此容易與U配位的是k2-A3和η2-A4，與水溶液條件下配位常數(shù)lgK計(jì)算結(jié)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

國家自然科學(xué)基金項(xiàng)目(21401152)；西南科技大學(xué)博士研究基金項(xiàng)目(13zx7130)；西南科技大學(xué)核廢物與環(huán)境安全國防重點(diǎn)學(xué)科實(shí)驗(yàn)室預(yù)研項(xiàng)目(15yyhk08)；西南科技大學(xué)核廢物與環(huán)境安全國防重點(diǎn)學(xué)科實(shí)驗(yàn)室團(tuán)隊(duì)項(xiàng)目(14tdhk01)

匙芳廷(1982—)，女，山東聊城人，博士，副教授，從事海水提鈾吸附劑研究與放射性廢物處理研究

*通信聯(lián)系人：文君(1985—)，男，四川樂山人，副研究員，放射化學(xué)專業(yè)，E-mail: junwen@caep.cn

TL941

A

0253-9950(2016)04-0238-09

10.7538/hhx.2016.38.04.0238