Multidecker Sandwich Cluster VnBenn+1 (n = 1, 2, 3, 4) as a Polarizable Bridge for Designing 1D Second-Order NLO Chromophore: Metal鈭捪€ Sandwich Multilayer St

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• 作者：Shu-Jian Wang ; Yin-Feng Wang ; Chenxin Cai
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：July 16, 2015
• 年：2015
• 卷：119
• 期：28
• 页码：16256-16262
• 全文大小：324K
• ISSN：1932-7455

文摘

Multidecker sandwich 蟺-coordination complexes with multiple metal atoms and cyclic 蟺-ligands can be considered as building blocks for designing NLO molecules. In a previous work, we found that multidecker sandwich complexes of the form V_nBz_n+1 (n = 1, 2, 3) can be considered as stronger electron donors than metallocene Fe(畏⁵-C₅H₅)₂ for the design of second-order NLO molecules, and a layer-number dependence of the first hyperpolarizability of V_nBz_n+1鈥?C₂H₂)₃鈥揘O₂ (n = 1, 2, 3) and the two-dimensional NLO character was observed from our calculation results. In the present article, by analogy with traditional donor鈥揳cceptor substituted conjugated polyenes, we took the multidecker sandwich complexes V_nBz_n+1 (n = 1, 2, 3, 4) as the polarizable bridge instead of the traditional 蟺-electron conjugated bridge and designed several novel push鈥損ull systems of the form donor鈥?V_nBz_n+1)鈥揳cceptor (n = 1, 2, 3, 4) by introducing electron-donating and electron-withdrawing groups at the terminal benzene ring of V_nBz_n+1. The NLO properties of these new species were investigated in detail. It was found that the first hyperpolarizability 尾₀ of the donor鈥?V_nBz_n+1)鈥揳cceptor complexes increases with the number of layers n for n = 1鈥?. However, when the number of layers was increased to 4, there was an apparent decrease in 尾₀, which is different from the behavior of traditional push鈥損ull 蟺-systems. To understand the optical transition and NLO response, time-dependent density functional theory (TD-DFT) calculations were carried out for these 1D chromophores. By analyzing the excited state that is crucial to the NLO response, we found that metal (d orbital) to 蟺-ligand (antibonding 蟺*-orbital) charge-transfer (MLCT) transitions indeed occur in the metal鈭捪€ sandwich multilayer structure and that small V_nBz_n+1 clusters (n = 2 or 3) could play a role in the polarizable bridge or CT axis. The findings from this quantum-chemical study should provide hints to scientists designing new organometallic multidimensional NLO molecules with metal鈭捪€ sandwich multilayer structures as new charge-transfer axes.