SHG-enhancement Study of Chained-Chromophores in their Polar Nematic Liquid Crystal Phase

采用密度泛函理论（DFT）B3 LYP/6- 31 G ^* 方法，通过计算（H2 N-（C6 H4 CONH）n-C6 H4 COOH）（AA低聚酰胺）和（H-（C6 H4 CONH）n-C6 H5）（BA低聚酰胺）的超极化率（β），研究了具有头尾结构的芳香族聚酰胺聚（4-氨基苯甲酸）的二次谐波性质. AA和BA低聚酰胺的β值随着酰胺键数目（n）的增加而增加。由于AA低聚酰胺的β值总是大于BA低聚酰胺的β值，因此对低聚酰胺的β值的终端效应是显著的。两能级模型将AA低聚酰胺大β的来源主要归因于基态和激发态之间的大跃迁矩。对于AA和BA低聚酰胺，激发能几乎是恒定的值，随着酰胺键的数目的增加，使涉及聚合的红移可能是小的。结果表明，聚4-氨基苯甲酸是一种新的具有倍频活性的生色团， 关于我们 ng效率-透明性的权衡问题，然后用密度泛函理论研究了N-甲基化对芳香酰胺的影响。苯甲酰苯胺（BA）为反式构象，其能量比顺式构象低4.60kcal/mol。而N-甲基苯甲酰苯胺（MBA）则为顺式构象，能量为3.23 kcal/mol，低于反式构象。N-甲基化对位连接芳香二酰胺化合物也通过DFT计算进行了研究，它们也倾向于顺式构象。由于存在两种稳定的构象（顺-顺和顺-顺-反），N-甲基化芳族聚酰胺除了失去主链的线性外，还具有大量的各种构象。此外，我们还对N-甲基化芳香二酰胺化合物进行了DFT计算，以验证其结构是否为手性结构。得到了N-甲基化芳香二酰胺六种稳定构象的相对能量。所有这些化合物都倾向于顺式构象，并且大多数是手性的。因此，它是实验上有趣的，以调查是否这些酰胺的chilarity诱导通过添加手性掺杂剂或没有。我们成功地观察到手性胺对N-甲基芳香酰胺的手性诱导作用。这一结果表明，N-甲基芳香酰胺可能是有用的作为一个建筑块，用于构建一个新的手性材料，如手性折叠体和液晶。少

SHG property of poly(4-aminobenzoic acid), an aromatic polyamide with head-tail structure, was investigated by calculating the hyperpolarizability (β) for (H_2N-(C_6H_4CONH)_n-C_6H_4COOH) (AA oligoamides) and (H-(C_6H_4CONH)_n-C_6H_5)(BA oligoamides) at density functional theory (DFT) B3LYP/6-31G^*. The β values of AA and BA oligoamides increase with increasing number of amide bonds (n). Since the β values of AA oligoamides are always larger than those of BA oligoamides, the terminal effect on the β value for oligoamides is significant. The two-level model ascribes the origin of the large β of AA oligoamides mainly to the large transition moment between the ground state and the excited state. For both AA and BA oligoamides, the excitation energies are almost constant values with increasing the number of amide bonds so that the red-shift involved with polymerization may be small. The result indicates that poly(4-aminobenzoic acid) is a new candidate of SHG-active chromophore for improvi … More ng efficiency-transparency trade-off problem.Then N-methylation effect on aromatic amides were investigated by using the DFT calculations. Benzanilide (BA) adopts the trans conformation with lower energy of 4.60 kcal/mol than cis one. On the other hand, N-methylbenzanilide (MBA) adopts the cis conformation with lower energy of 3.23 kcal/mol than trans one. N-methylated para-linked aromatic diamide compounds were also studied by the DFT calculations and they also prefer the cis conformation. Since there are two stable conformations (cis-cis-syn and cis-cis-anti), N-methylated aromatic polyamides have enormous various conformations in addition to losing linearity of main chains. As a result, N-methylated aromatic polyamides is not liquid crystal but amorphous.Moreover, we studied various N-methylated aromatic diamide compounds by using the DFT calculations in order to check these structures are chiral or not. The relative energies for six stable conformers for N-methylated aromatic diamides were obtained. All of these compounds prefer the cis conformation, and most of them are chiral. Therefore, it is experimentally interesting to investigate whether the chilarity of these amides are induced by addition of a chiral dopant or not. We succeeded in observation of chirality induction on N-methy aromatic amides with chiral amines. This result indicates that N-methyl aromatic amides may be useful as a building block for constructing a new chiral material such as a chiral foldamer and liquid crystal. Less