Wang Wen-Yong, Wang Li, Ma Na-Na, Zhu Chang-Li, Qiu Yong-Qing
Institute of Functional Material Chemistry, Faculty of Chemistry, Northeast Normal University, Changchun 130024, Jilin, People's Republic of China.
Dalton Trans. 2015 Jun 7;44(21):10078-88. doi: 10.1039/c5dt01134e.
The electron donor-acceptor complexes, which undergo intramolecular charge transfer under external stimulus, are an emerging class of materials showing important application in nonlinear optics. Synthesizing ferrocene/fullerene complexes through face-to-face fusion would enjoy the merits of both ferrocene and fullerene due to their strong donor-acceptor interactions. Four ferrocene/fullerene hybrid complexes with the gradual extension of fullerene cage size, including CpFe(C60H5), CpFe(C66H5), CpFe(C70H5), and CpFe(C80H5) (Cp is cyclopentadienyl), have been investigated by density functional theory. These hybrid molecules give eclipsed and staggered isomers. The main reason that the eclipsed isomer is stable is that the eclipsed structure possesses large CpFefullerene bonding energy. The CpFefullerene interaction is smaller than that of CpFefullerene, which must come from two different interfaces. The presence of covalent bond character between CpFe and fullerene is supported by the localized orbital locator, deformation of electron density distribution and energy decomposition analysis. Significantly, the absorption bands and first hyperpolarizabilities of these hybrid complexes are strongly sensitive to the fullerene cage size, which is ascribed to a change in the charge transfer pattern, especially for CpFe(C80H5), which displays reverse π → π* charge transfer from bottom to top cage, leading to notable hyperpolarizability. Investigation of the structure-property relationship at the molecular level can benefit the design and preparation of such hybrid complexes in chemistry and materials science.
电子给体-受体复合物在外部刺激下会发生分子内电荷转移，是一类新兴材料，在非线性光学中显示出重要应用。通过面对面融合合成二茂铁/富勒烯复合物，由于它们之间强烈的给体-受体相互作用，将兼具二茂铁和富勒烯的优点。利用密度泛函理论研究了四种随着富勒烯笼尺寸逐渐增大的二茂铁/富勒烯杂化复合物，包括CpFe(C60H5)、CpFe(C66H5)、CpFe(C70H5)和CpFe(C80H5)（Cp为环戊二烯基）。这些杂化分子存在重叠式和交叉式异构体。重叠式异构体稳定的主要原因是重叠结构具有较大的CpFe-富勒烯键能。Cp-富勒烯的相互作用小于CpFe-富勒烯的相互作用，这一定源于两个不同的界面。定域轨道定位器、电子密度分布变形和能量分解分析支持了CpFe与富勒烯之间共价键特征的存在。值得注意的是，这些杂化复合物的吸收带和第一超极化率对富勒烯笼尺寸非常敏感，这归因于电荷转移模式的变化，特别是对于CpFe(C80H5)，它显示出从笼底部到顶部的反向π→π*电荷转移，导致显著的超极化率。在分子水平上研究结构-性质关系有助于化学和材料科学中此类杂化复合物的设计和制备。
