In-Plane Thorium(IV), Uranium(IV), and Neptunium(IV) Expanded Porphyrin Complexes

Here we report the first series of in-plane thorium­(IV), uranium­(IV), and neptunium­(IV) expanded porphyrin complexes. These actinide (An) complexes were synthesized using a hexa-aza porphyrin analogue, termed dipyriamethyrin, and the nonaqueous An­(IV) precursors, ThCl4(DME)2, UCl4, and NpCl4(DME)2. The molecular and electronic structures of the ligand, each An­(IV) complex, and a corresponding uranyl­(VI) complex were characterized using nuclear magnetic resonance (NMR) and UV–vis spectroscopies as well as single-crystal X-ray diffraction analysis. Computational analyses of these complexes, coupled to their structural features, provide support for the conclusion that a greater degree of covalency in the ligand–cation orbital interactions arises as the early actinide series is traversed from Th­(IV) to U­(IV) and Np­(IV). The axial ligands in the present An­(IV) complexes proved labile, allowing for the electronic features of these complexes to be further modified.本文首次报道了一系列面内型四价钍、四价铀及四价镎扩展卟啉配合物（expanded porphyrin complex）。这些锕系元素（An）配合物以六氮杂卟啉类似物二吡亚甲卟啉（dipyriamethyrin）以及非水四价锕系前驱体ThCl4(DME)2、UCl4和NpCl4(DME)2为原料合成。本研究通过核磁共振（NMR）、紫外-可见（UV–vis）光谱及单晶X射线衍射分析，对该配体、各四价锕系配合物以及相应的六价铀酰（uranyl(VI)）配合物的分子与电子结构进行了表征。对这些配合物的计算分析结合其结构特征，证实了随着锕系早期元素从四价钍到四价铀再到四价镎依次变化，配体与阳离子间的轨道相互作用中共价程度显著提升这一结论。本研究中四价锕系配合物的轴向配体具有易取代性，可对这些配合物的电子特性进行进一步修饰。