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Multidecker Sandwich Complexes VnBenn+1 (n = 1, 2, 3) as Stronger Electron Donor Relative to Ferrocene for Designing High-Performance Organometallic Second-Order NLO Chromophores: Evident Layer Effect on the First Hyperpolarizability and Two-Dimensional NLO Character

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journal contribution
posted on 12.03.2015, 00:00 authored by Shu-Jian Wang, Yin-Feng Wang, Chenxin Cai
During the past 3 decades, significant progress has been made in multidecker sandwich complexes. Replacing metallocene in the metallocene-based second-order nonlinear optical chromophores with multidecker sandwich complexes will create a variety of new second-order NLO organometallic complexes. To explore the possibility of improving NLO properties of organometallic complexes by using multidecker sandwich complexes, we theoretically design five second-order NLO moleculars VnBzn+1-(C2H2)3-NO2 (n = 1, 2, 3) with widely investigated VnBzn+1 (n = 1, 2, 3) by changing the layer number n or position of conjugation π–A system in the D−π–A structure. The NLO properties of these five complexes are investigated in detail. By comparison with the β0 of ferrocenyl derivative Fe­(η5-C5H5)2-(C2H2)3-NO2, the larger NLO response (β0, 10215–36917 au) is found in VnBzn+1-(C2H2)3-NO2 (n = 1, 2, 3). The dependence of the first hyperpolarizabilities β0 on the layer number n and the position of conjugation π–A system is discussed in the article. The evident layer effect on the first hyperpolarizabilities β0 is shown. And, the enlargement of the first hyperpolarizability β0 by the layer number n can be rationalized by considering the enhancement of parallel-x-MLCT (from more than one metal center to acceptor, −NO2), perpendicular-x-MLCT (from multiple metal centers to multiple C6H6 ligands) transition and two-dimensional NLO character with the two charge transfer axes. By comparison with ferrocene or V1Bz2, the multidecker sandwich complexes VnBzn+1 (n = 2, 3) can be considered as stronger donor group for designing NLO moleculars. We hope, this groundbreaking work may evoke one’s attention to design new, highly efficient second-order NLO molecular materials with excellent building blocks: multidecker sandwich complexes.