水溶液中四种脱氧核苷酸与水合铀酰离子相互作用的理论计算

运用密度泛函理论(DFT)方法 M06-2X,在相对论有效势基组水平下研究水溶液中水合铀酰脱氧核苷酸配合物[UO2(dNMP)(H2O)3]2+(d NMP=单磷酸脱氧核苷酸)的几何结构、能量和电子结构等性质,采用极化连续介质模型考虑水溶剂环境。结果表明,除了脱氧胸苷酸,其它脱氧核苷酸均以磷酸基团P=O键与铀原子形成的配位结构最稳定,4类配离子U=O键长值较接近,但配位键键长有所不同。脱氧腺苷酸配离子的总结合能最大,但脱氧腺苷酸变形能最小。振动光谱分析发现U=O键和P=O键伸缩振动频率均发生红移,脱氧腺苷酸配离子的变化程度最大。电子密度拓扑分析表明U-dNMP键和U-OH2键具有离子键性质。电荷转移分析显示配体片段向铀酰离子发生了电子转移,脱氧腺苷酸配离子中配体转移的电荷数最多。轨道成分分析表明,高占据轨道贡献主要来自脱氧核苷酸配体π轨道,而低阶空轨道基本是U的5f轨道组成,脱氧鸟苷酸配离子的HOMO-LUMO能级差最小。     

一系列水合和非水合铀酰卤族(F,Cl,Br)配合物在水溶液中的结构和紫外吸收光谱性质的密度泛函理论研究

本文考虑相对论效应并应用密度泛函理论(DFT)研究水溶液中UO2Xn(H2O)5-n(X=F,Cl,Br;n=1～4)和UO2Xn(X=F,Cl,Br;n=1～6)一系列水合和非水合铀酰化合物的结构和紫外吸收光谱性质。将这一系列物质命名为Xnm(X为F,Cl,和Br;n为卤素配体个数,m为水分子配体的个数)。在水溶液中,溶剂化效应采用类导体屏蔽模型(COSMO)并采用SAS溶剂接触曲面构造空穴模拟水溶剂对配合物的作用。配合物的紫外光谱性质采用考虑旋-轨耦合相对论效应的含时密度泛函(SO-TD-DFT)进行计算。U=O键随着F配体数目的增加而明显伸长,然而随Cl和Br配体数目的增加变化较小。随X配体数目的增加和水分子参与配位,铀与X的结合能逐渐减弱。配合物的紫外光谱计算表明铀酰氟的各种配合物并不出现特征吸收峰,而铀酰氯和铀酰溴的各种配合物均有特征吸收光谱。通过分子轨道分析可以很好解释光谱所体现的特征。     

相对论赝势的从头计算法研究铀酰离子电子结构

用相对论赝势的从头算法研究了铀酰离子的几何构型和电子结构.得到了与实验数据较一致的键长、键角和IR振动频率.铀氧间以U5f与O2p相互作用为主,U6d与O2p间的键合较小;同时,U6p、U7s、U6d和Usd杂化轨道与O2s间也有强的相互作用.不同自旋多重度时对铀酰离子总能量计算结果表明,UO22+的基态为1∑g+的可能性更大.     

聚吡咯铀酰氧-酰亚胺配合物结构、振动光谱和基团交换反应的相对论密度泛函理论计算

铀酰氧-酰亚胺混合型配合物的合成为热力学稳定、动力学惰性铀酰（UO₂²⁺）和等电子体系铀酰亚胺（U（NR）₂²⁺）研究建立了纽带. 使用相对论密度泛函理论计算“Pacman”结构配合物[（THF）（OU^VIE）（A₂L）]（E=O、NH、NMe和NPh; A=H和Li; L为八齿氮供体低聚吡咯大环配体）. 优化得到U=O/U=N距离与实验值符合; 键级和电子结构分析显示U=O_exo/U=N有部分三重键特征; 由于受Li离子扰动,U=O_endo强度则介于单键和双键之间. 计算表明O=U=NH和O=U=O成键相近,均具有对称和反对称伸缩振动频率,而取代基Me和Ph耦合作用使得U=N-C吸收峰出现在高频区域. 酰氧和酰亚胺基团交换反应计算发现独特Pacman结构配合物的反应能相对五角双锥型配合物的有所降低,其中=O与=NMe交换反应最易实现; A离子变换不但能调控配合物结构和特征振动谱,还可降低基团交换反应能.     

金红石TiO2纳米团簇与铀酰相互作用的相对论密度泛函理论计算

采用全电子相对论密度泛函理论方法探索金红石型Ti O_2纳米团簇与铀酰的相互作用。考察金红石团簇模型(包括层数和表面积大小)变化对吸附铀形成复合物结构、吸附作用能等性质的影响,确定2层、表面积为1.1 nm×0.6 nm、包括63个原子的纳米团簇(标记为2L-Ti15)能够合理描述金红石纳米粒子性质的同时,还能节约计算资源。对2L-Ti15-[(UO_2)(H_2O)_3]~(2+)复合物计算表明,纳米团簇和铀酰存在共价键作用;优化得到U-O_(surf)键长0.233~0.238 nm,这一距离在已发现铀酰基配合物U-O距离范围内。在气相条件下,纳米团簇对铀酰吸附反应为放热过程(-3.02 e V);考虑溶剂介质环境的影响,反应则需要吸收少许能量(0.16e V)。U-O_(surf)键的能量分解发现,纳米团簇和铀酰的化学键作用为轨道相互作用主导的(占94%),它的静电吸引略大于Pauli排斥。基于电子密度的QTAIM(quantum theory of atoms in molecule)分析揭示,U-O_(surf)作用是介于离子和共价之间的配位键,其强度高于复合物中的U-OH_2键作用,但比U=O键弱。波函数分析表明,来自纳米团簇的O(2p)贡献HOMO轨道,并混有σ(U=O)成键性质,而LUMO轨道则为Ti(3d)修饰的U(5f)性质,复合物HOMO-LUMO带隙为2.40 e V,相对吸附前的纳米团簇半导体粒子的3.35 e V变窄。从吸收光谱角度而言,复合物体系可能在可见光区域具有更强的捕光性能。     

铀酰-Salophen受体对α, β-不饱和羰基化合物及手性客体的分子识别

基于密度泛函理论(DFT)的计算方法,研究了不对称铀酰-salophen受体对α, β-不饱和羰基化合物客体及手性小分子的分子识别。理论计算结果表明:配合物中受体的U原子与客体的O3原子配位,且受体与客体之间结合能随受体上芳环取代基的增大而增大; R₂, R₃-系列配合物中U―O3键的稳定性比R₁-系列的更强;配位后的α, β-不饱和羰基化合物中C＝C与C＝O之间的共轭效应减弱。而且,通过圆二色谱(CD)及结合能计算表明:芘基铀酰-salophen (受体3)对(R)-1-(2-萘基)乙胺的分子识别选择性优于(S)-1-(2-萘基)乙胺。因而,这些研究结果为不对称铀酰-salophens具有分子识别能力提供了新的信息。     

UO22+·nH2O和PuO22+·nH2O(n=2,4,5,6)密度泛函理论研究

首先用密度泛函理论(DFT)方法研究了铀酰和钚酰离子的几何与电子结构,计算结果与实验基本符合,表明DFT方法也能用于含铀和钚重原子的化合物计算.然后对铀酰和钚酰水合离子的几何构型、Mulliken集居数分布以及铀酰(钚酰)与配体水分子的结合能进行计算,计算结果表明UO22+·5H2O和PuO22+·5H2O分别为铀酰和钚酰系列水合离子中最稳定的配合物.     

Ce（H2O）n3+（n=1～6）水合性质的密度泛函理论研究

以TZ2P为基组,采用Becke- Perdew(BP)等10种密度泛函分别对Ce(H2O)n3+(n=1～6)体系进行几何优化.运用绝对平均误差分析得出在所计算的10种密度泛函中Becke-PBEc为最优泛函.振动光谱分析表明,Ce(H2O)n3+(n=1～6)体系随着n增大,即H2O配位数的增加,Ce和O之间的相互作用越来越弱,O和H之间的相互作用越来越强,振动吸收频率与键长的呈现良好的线性关系.电子结构分析表明,f轨道的孤对电子不参与Ce—O之间的成键.热力学分析表明,Ce3+不易形成低配位的水合离子,但是在适当温度压强以及动力学条件下铈的低配位水合离子有可能实现转变.     

气相和水溶液中铀酰配合物UO2Ln^2-n＊a（L=F^-,CO3^2-,NO3^-;n=0-6,a=1,2）的结构和振动光谱

通过对铀采用相对赝势基组,其它原子使用6-31＋G（d）基组,应用密度泛函理论（DFT）以及B3LYP方法对UO22＋离子与F-、CO23-和NO-3的各配位结构进行优化和频率计算.计算考虑了气相和水溶剂化两种状态,其中溶剂化模型采用连续导体介质理论模型（CPCM）.计算结果显示配体的配位数与O襒U襒O对称伸缩振动频率存在线性关系.配体在气相和水溶液中存在的关系基本符合通式：νs=-Agasn＋983和νs=-Aaqn＋821（Agas和Aaq为常数,表示每增加一个配体振动频率的变化值;n为配体配位数）.其中F-对应Agas=53cm^-1,Aaq=11cm^-1;CO230-对应Agas=85cm^-1,Aaq=19cm^-1;NO-3对应Agas=48cm^-1,Aaq=-10cm^-1.并且Aaq值与实验值一致.     

六聚吡咯大环与铀/超铀酰基离子相互作用:成键、热力学和光谱性质

采用全电子相对论密度泛函理论探索多种六聚吡咯大环锕酰基配合物(nAn;n=1~3;An=U,Np and Pu)的电子结构本质、成键规律和化学反应特性。结构优化发现大环配体空穴大小与锕酰离子尺寸相当时,配合物锕酰基采用性对规则的六角双锥结构,而当空穴尺寸相对大时,配合物则采取扭曲结构以降低体系能量。当配体相同时,随着铀、镎、钚变化,An=O伸缩振动频率逐渐变小,这与优化的键长和键级变化规律相一致。QTAIM(quantum theory of atoms in molecule)拓扑分析显示An-N为弱共价单键特征,具有较大离子性成分。依据不同铀源,得到与大环配体的反应自由能均小于146 kJ·mol~(-1),与实验合成配合物的反应能计算数值相当。对含铀配合物电子吸收光谱计算显示,低能(近红外和可见光区)的吸收带具有全部或较大的配体→金属电荷转移性质贡献。     

Self-interaction artifacts on structural features of uranyl monohydroxide from Kohn�CSham calculations

Invoking a DFT?+?U approach, we explored self-interaction artifacts in results from Kohn?CSham (KS) density functional calculations on the geometry and the vibrational frequencies of uranyl monohydroxide and the corresponding tetra-aqua complex. Exchange?Ccorrelation functionals based on the local density approximation (LDA) and the generalized-gradient approximation (GGA) predict equilibrium geometries for [UO₂(OH)]⁺ that deviate from the results of hybrid DFT calculations and high-level wavefunction-based methods such as CCSD(T). LDA?+?U and GGA?+?U functionals with corrections for the insufficient localization of the U 5f shell yield better agreement, in particular for the angle U-O_h-H. At the LDA level, a linear coordination of the OH ligand results; with the +U correction, the angle U-O_h-H is reduced by ~35°, in good agreement with CCSD(T) results. At the GGA level, the bending angle is changed by ~20°. This relatively strong self-interaction artifact is traced back to a spurious ?? interaction between U 5f and O(p) orbitals which is less pronounced in the presence of further (aqua) ligands.     

Binuclear Uranium(VI) Complexes with a “Pacman” Expanded Porphyrin: Computational Evidence for Highly Unusual Bis‐Actinyl Structures

On the basis of uranyl complexes reacting with a polypyrrolic ligand (H₄L), we explored structures and reaction energies of a series of new binuclear uranium(VI) complexes using relativistic density functional theory. Full geometry optimizations on [(UO₂)₂(L)], in which two uranyl groups were initially placed into the pacman ligand cavity, led to two minimum‐energy structures. These complexes with cation–cation interactions (CCI) exhibit unusual coordination modes of uranyls: one is a T‐shaped ( T ) skeleton formed by two linear uranyls {O_exo?U₂?O_endo→U₁(?O_exo)₂}, and another is a butterfly‐like ( B ) unit with one linear uranyl coordinating side‐by‐side to a second cis‐uranyl. The CCI in T was confirmed by the calculated longest distance and lowest stretching vibrational frequency of U₂?O_endo among the four U?O bonds. Isomer B is more stable than T , for which experimental tetrameric analogues are known. The formation of B and T complexes from the mononuclear [(UO₂)(H₂L)(thf)] ( M ) was found to be endothermic. The further protonation and dehydration of B and T are thermodynamically favorable. As a possible product, we have found a trianglelike binuclear uranium(VI) complex having a O?U?O?U?O unit.     

Intermolecular interactions in uracil–nitrous acid complexes: structures,binding energy,topological properties,and nuclear magnetic resonance study

Molecular interactions between uracil and nitrous acid (U–NA) [C₄N₂O₂H₄? NO₂H] have been studied using B3LYP, B3PW91, and MP2 methods with different basis sets. The optimized geometries, harmonic vibrational frequencies, charge transfer, topological properties of electron density, nucleus‐independent chemical shift (NICS), and nuclear magnetic resonance one‐ and two‐bonds spin–spin coupling constants were calculated for U–NA complexes. In interaction between U and NA, eight cyclic complexes were obtained with two intermolecular hydrogen bonds N(C)HU…N(O) and OH_NA…O_U. In these complexes, uracil (U) simultaneously acts as proton acceptor and proton donor. The most stable complexes labeled, UNA1 and UNA2, are formed via NH bond of U with highest acidity and CO group of U with lowest proton affinity. There is a relationship between hydrogen bond distances and the corresponding frequency shifts. The solvent effect on complexes stability was examined using B3LYP method with the aug‐cc‐pVDZ basis set by applying the polarizable continuum model (PCM). The binding energies in the gas phase have also been compared with solvation energies computed using the PCM. Natural bond orbital analysis shows that in all complexes, the charge transfer takes place from U to NA. The results predict that the Lone Pair (LP)(O)_U → σ*(O? H) and LP(N(O)_NA → σ*(N(C)? H)_U donor–acceptor interactions are most important interactions in these complexes. Atom in molecule analysis confirms that hydrogen bond contacts are electrostatic in nature and covalent nature of proton donor groups decreases upon complexation. The relationship between spin–spin coupling constant (^1hJ_H…_Y and ^2hJ_H…_Y) with interaction energy and electronic density at corresponding hydrogen bond critical points and H‐bonds distances are investigated. NICS used for indicating of aromaticity of U ring upon complexation. © 2013 Wiley Periodicals, Inc.     

Estimation of coordination bond energies of NH3, H2O and Et2NH ligands in the Ni(II) and Cu(II) complexes

Tridentate ligands 2-hydroxyphenylsalicylaldimine (SAPH₂), 2-hydroxyphenyl-2-hydroxy-1-naphtalaldimine (NAPH₂) and Ni(II) complexes with multidentate ligand Bis-N·N′-(salicylidene)-1,3-propanediamine (LH₂) as well as mononuclear complex of Cu(II) were prepared using the same multidentate ligand. Diethylamine (Et₂NH), NH₃ and H₂O monodentate ligands were bound to these complexes coordinatively. The heat absorbed at the temperatures where these ligands thermally dissociated from the complexes were measured using the TG and DSC methods. It is assumed that the states both of the complexes with and without the monodentate ligands are solid and coordination bond energy for the monodentate ligand is calculated. It is seen that these calculated coordination bond energies are comparable with hydrogen bond energies.     

2,7-萘二磺酸阴离子导向五元瓜环基超分子自组装体的制备及其荧光检测性能

通过引入2,7-萘二磺酸(2,7-NDA^2-)阴离子作为结构导向剂,与五元瓜环(Q[5])和过渡金属离子(Co²⁺、Ni²⁺、Zn²⁺、Cd²⁺)在水热条件下制备了4种新颖的Q[5]基超分子自组装体(Q[5]-SA),即{[M(H₂O)4(Q[5])]·(NDA)}·x H₂O(M=Co (1)、Ni (2)、Zn (3))和{[Cd2Cl2(H₂O)4(Q[5])]·(NDA)}·13H₂O (4)。单晶X射线衍射测试结果表明,自组装体1～3同构,其中Q[5]仅一端的部分端口羰基氧原子与金属离子配位形成简单配合物;而4中Q[5]的2个端口均与金属离子Cd²⁺配位形成了一维配位链。在自组装体1～4中,配体2,7-H2NDA均全脱质子,形成2,7-NDA2-阴离子平衡体系电荷,但均未能与金属离子配位,而在2,7-NDA2-阴离子与Q[5]外壁之间的瓜环外壁作用下进一步形成...     

2，7-萘二磺酸导向构筑的五元瓜环-碱金属及碱土金属基超分子自组装体及其溶剂识别

以2,7-萘二磺酸（2,7-H₂NDA）作为结构导向剂,与五元瓜环（Q[5]）和碱金属、碱土离子（K⁺、Rb⁺、Mg²⁺、Ca²⁺）在水热条件下制备出了4种新颖的Q[5]基超分子自组装体[K₂（H₂O）₄（Q[5]）]（2,7-NDA）·4H₂O （1）、[Rb₂（H₂O）₅（Q[5]）]（2,7-NDA）·3H₂O （2）、[Mg （H₂O）₄（Q[5]）]（2,7-NDA）·8H₂O （3）和[Ca （H₂O）₄（Q[5]）]（2,7-NDA）·10H₂O （4）。单晶X射线衍射测试结果表明,自组装体1和2具有相同的结构： Q[5]分子与金属离子配位形成的是“分子胶囊”;而在3中Q[5]与Mg²⁺配位形成的是1：1型简单配合物结构;在自组装体4中,Q[5]与Ca²⁺配位形成的是一维Q[5]-Ca²⁺配位聚合物链结构。这些结构中2,7-NDA^2-阴离子平衡了体系电荷,且通过其与瓜环外壁之间的弱相互作用,促进自组装体最终构筑成三维超分子结构。此外,还研究了自组装体4的溶剂识别荧光传感性能,结果表明其能够作为有机溶剂丙酮和DMF的猝灭型荧光探针。