Binuclear Uranium(VI) Complexes with a “Pacman” Expanded Porphyrin: Computational Evidence for Highly Unusual Bis‐Actinyl Structures |
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| Authors: | Qing‐Jiang Pan Dr. Grigory A. Shamov Dr. Georg Schreckenbach Prof. |
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| Affiliation: | 1. Department of Chemistry, University of Manitoba, Winnipeg, MB, R3T 2N2 (Canada), Fax: (+1)?204‐474‐7608;2. Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education and Laboratory of Physical Chemistry, School of Chemistry and Materials Science, Heilongjiang University, Harbin 150080 (PR China) |
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| Abstract: | 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 {Oexo?U2?Oendo→U1(?Oexo)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?Oendo 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. |
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| Keywords: | cation– cation interactions density functional calculations macrocycles pacman‐like complexes uranium |
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