Ligand size dependence of U-N and U-O bond character in a series of uranyl hexaphyrin complexes: quantum chemical simulation and density based analysis.
Ligand size dependence of U-N and U-O bond character in a series of uranyl hexaphyrin complexes: quantum chemical simulation and density based analysis.
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DOI：
10.1039/c6cp08783c
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发表时间：
2017-03
期刊：
影响因子：
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通讯作者：
P. Di Pietro;A. Kerridge
中科院分区：
文献类型：
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作者：
P. Di Pietro;A. Kerridge
在密度泛函理论水平上研究了一系列铀酰与六卟啉配体的配合物，并使用各种基于密度的技术进行了分析。确定的配体的大小和复杂的稳定性之间的关系，由卟啉环中的中间碳中心的存在下控制。与最小的配体，环[6]吡咯的配合物，被发现具有增强的共价特性，在赤道U-N键定义的量子理论的原子在分子中（QTAIM），以及增强的稳定性，相比，较大的配合物。QTAIM数据支持的电子密度差分布，综合电子性能和分析的约化密度梯度（RDG），这都表明明确的证据，电子共享在所有的U-N键。在所有配合物中，发现与自由铀酰相比，共价轴向铀-氧酰基相互作用减弱，有证据表明电子电荷分离导致离子相互作用更强。的U-N键的共价字符和铀酰电荷重新分配的幅度之间的关系被确定，其中更大的U-N相互作用的共价字符，更离子的U-Oyl相互作用出现。与最大的配体，hexaphyrin（1.1.1.1.1）的配合物，被发现有额外的相互作用与铀酰氧中心，扰乱U-Oyl相互作用。
A series of uranyl complexes with hexaphyrin ligands are investigated at the density functional level of theory and analysed using a variety of density-based techniques. A relationship is identified between the size of the ligand and the stability of the complex, controlled by the presence of meso-carbon centres in the porphyrin ring. The complex with the smallest ligand, cyclo[6]pyrrole, is found to have enhanced covalent character in equatorial U-N bonds as defined by the quantum theory of atoms in molecules (QTAIM), as well as enhanced stability, compared to the larger complexes. QTAIM data are supported by electron density difference distributions, integrated electronic properties and analysis of the reduced density gradient (RDG), which all show unambiguous evidence of electron sharing in all U-N bonds. In all complexes, a weakening of the covalent axial U-Oyl interaction in comparison to free uranyl is found, with evidence for a separation of electronic charge resulting in a more ionic interaction. A relationship between covalent character in the U-N bonds and the magnitude of uranyl charge redistribution is identified, where the greater the covalent character of the U-N interaction, the more ionic the U-Oyl interaction appears. The complex with the largest ligand, hexaphyrin(1.1.1.1.1.1), is found to have additional interactions with the uranyl oxygen centres, perturbing the U-Oyl interaction.