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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Interaction between Monomeric Units of Donor-Acceptor-Functionalized Azobenene Dendrimers:Effects on Macroscopic Configuration and First Hyperpolarizability
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Interaction between Monomeric Units of Donor-Acceptor-Functionalized Azobenene Dendrimers:Effects on Macroscopic Configuration and First Hyperpolarizability

机译：供体-受体功能化的偶氮苯树枝状大分子单体单元之间的相互作用：对宏观构型和第一次超极化的影响。

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To find out why azobenzene dendrimers, which are branched three-dimensional macromolecules with a branch point at each of the donor—acceptor-functionalized azobenzene monomeric units, have large first hyper-polarizabilities, we used theoretical calculations for three types of dimers: (I) two azobenzenes linked covalently head-to-tail; (2) linear dimers where the two azobenzenes are nearly superimposable on the covalently bonded dimers but are not covalently linked; (3) parallel dimers where the two azobenzenes are roughly side by side. We found from ab initio calculations that the optimized geometry is roughly linear for the first type and is nearly parallel and slightly staggered for the third type. We also found that the first hyperpolarizabilities for the linear dimers are larger than those obtained from the sum of the hyperpolarizability tensors for the individual monomers and that those for the parallel dimers are smaller. These findings led us to conclude that the noncentrosymmetric arrangement of the monomeric units forming the azobenzene dendrimers, which causes the large first hyperpolarizabilities, can be partly ascribed to the interaction between the monomeric units and the first hyperpolarizability is increased by the interaction between monomeric units arranged in series. In addition, calculations based on electrical interaction models showed that the changes of the first hyperpolarizability that are due to the interaction between the monomeric units can be qualitatively explained in terms of classical electrostatic interaction, whereas quantum mechanical interactions and/or a more complete electrostatic model need to be considered in accounting for the extent of these changes quantitatively.
机译：为了弄清为什么偶氮苯树枝状大分子是在每个供体（受体官能化的偶氮苯单体单元）上都有一个分支点的支化三维大分子，因此我们对三种类型的二聚体使用了理论计算： ）两个头尾共价连接的偶氮苯; （2）直链二聚体，其中两个偶氮苯几乎重叠在共价键合的二聚体上，但不共价连接; （3）平行的二聚体，其中两个偶氮苯大致并排。从头算开始，我们发现优化的几何形状对于第一种类型大致是线性的，而对于第三种类型则几乎是平行的并且稍微交错。我们还发现，线性二聚体的第一超极化率大于从单个单体的超极化率张量之和获得的值，而平行二聚体的超极化率则较小。这些发现使我们得出结论，形成偶氮苯树枝状大分子的单体单元的非中心对称排列，会引起较大的第一超极化性，部分原因在于单体单元之间的相互作用，并且第一超极化性通过排列的单体单元之间的相互作用而增加。系列。另外，基于电相互作用模型的计算表明，由于单体单元之间的相互作用而引起的第一超极化率的变化可以用经典的静电相互作用来定性地解释，而量子力学相互作用和/或更完整的静电模型在定量考虑这些变化的程度时需要考虑。

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