Electronic Coupling in [Mo2]鈥揃ridge鈥揫Mo2] Systems with Twisted Bridges
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- 作者：Hong Li Zhang ; Guang Yuan Zhu ; Gangyi Wang ; Miao Meng ; Chun Y. Liu ; Hao Lei
- 刊名：Inorganic Chemistry
- 出版年：2015
- 出版时间：December 7, 2015
- 年：2015
- 卷：54
- 期：23
- 页码：11314-11322
- 全文大小：493K
- ISSN：1520-510X
文摘
In order to evaluate the impact of bridge conformation on electronic coupling in donor鈥揵ridge鈥揳cceptor triad systems, two Mo2 dimers, [Mo2(DAniF)3]2[渭-1,4-{C(O)NH}2-Naph] (1, DAniF = N,N鈥?di(p-anisyl)formamidinate and Naph = naphthalenyl) and [Mo2(DAniF)3]2[渭-1,4-(CS2)2-2,5-Me2C6H2] (2), have been synthesized and structurally characterized. These two compounds feature a large dihedral angle (>60掳) between the central aromatic ring and the plane defined by the Mo鈥揗o bond vectors, which is distinct from the previously reported phenylene bridged analogues [Mo2(DAniF)3]2[渭-1,4-{C(O)NH}2-ph] (I) and [Mo2(DAniF)3]2[渭-1,4-(CS2)2-C6H4] (II), respectively. Unusual optical behaviors are observed for the mixed-valence (MV) species (1+ and 2+), generated by single-electron oxidation. While 2+ exhibits a weak intervalence charge transfer (IVCT) absorption band in the near-IR region, the IVCT band is absent in the spectrum of 1+, which is quite different from what observed for I+ and II+. Optical analyses, based on superexchange formalism and Hush model, indicate that, in terms of Robin鈥揇ay classification, mixed-valence species 1+ belongs to the electronically uncoupled Class I and complex 2+, with Hab = 220 cm鈥?, is assigned to the weakly coupled Class II. Together with I+ and II+, the four MV complexes complete a transition from Class I to Class II鈥揑II borderline as a result of manipulating the geometric topology of the bridge. Given the structural and electronic features for the molecular systems, the impacts of electrostatic interaction (through-space) and electron resonance (through-bond) on electronic coupling are discussed.