Push–pull tetraene chromophores derived from dialkylaminophenyl, tetrahydroquinolinyl and julolidinyl moieties: optimization of second-order optical nonlinearity by fine-tuning the strength of electron-donating groups
Push–pull tetraene chromophores derived from dialkylaminophenyl, tetrahydroquinolinyl and julolidinyl moieties: optimization of second-order optical nonlinearity by fine-tuning the strength of electron-donating groups
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DOI：
10.1039/c2jm32848h
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发表时间：
2012-07
影响因子：
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通讯作者：
Xing‐Hua Zhou;Jingdong Luo;J. Davies;Su Huang;A. Jen
中科院分区：
文献类型：
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作者：
Xing‐Hua Zhou;Jingdong Luo;J. Davies;Su Huang;A. Jen
基于三种不同类型的电子给体，分别是二乙氨基苯基、四氢喹啉基和胡萝卜烷基，合成了一系列具有相同异佛尔酮四烯桥和强CF3-TCF受体的高极化率发色团1-3。随着局部介电环境和极化诱导的偏心有序化，这些生色团的供电子强度逐渐增加，允许微调它们的分子基态极化，对于非常大的超极化率(β)来说，这是非常接近最佳的。溶剂变色研究和密度泛函理论计算表明，在大多数极性溶剂中，更多具有较强给体基团的偶极生色团2和3可以被极化到接近花菁极限的位置，甚至进入两性离子区域，从而使溶剂变色反转，β值减小。这与1的二乙氨基苯基给体在所有被测试的溶剂中具有类似多烯的特性形成了鲜明的对比。最有趣的是，电场极化引起了它们极化薄膜中生色电荷转移吸收带的位置、强度和形状的显著变化。结果表明，固体中分子间的非平凡相互作用可以改变作用于极化和去极化薄膜中的发色团的反应场，并显著影响它们的电光活性。结果表明，1/PMMA和2/PMMA中含有10wt%生色团的客体聚合物的电致发光系数为∼80 pm V−1，而3/PMMA的EO系数急剧下降至20 pm V−1。这些系统的分析导致了一种新的客体-宿主EO聚合物的合理设计，该聚合物含有35wt%的空间修饰生色团AJLZ55，在1.31−m处获得了218 pm Vμ1的超高EO系数。
A series of highly polarizable chromophores 1–3 has been synthesized based on three different types of electron donors, including diethylaminophenyl, tetrahydroquinolinyl and julolidinyl groups respectively, with the same isophorone-derived tetraene bridges and strong CF3–TCF acceptors. The progressively increased electron-donating strength for these chromophores allows for the fine-tuning of their molecular ground-state polarization, being very close to optimal for very large hyperpolarizability (β), as a function of the local dielectric environment and poling-induced acentric ordering. The solvatochromic study and DFT calculations suggested that more dipolar chromophores 2 and 3 with stronger donating groups can be polarized quite close to the cyanine limit, or even beyond that into the zwitterionic regime in the most polar solvents to give the inverted solvatochromism and diminished β values. This is in stark contrast to the polyene-like characteristic of 1 with the diethylaminophenyl donor in all the tested solvents. Most intriguingly, the electric field poling has induced significant changes in the position, intensity and shape of the chromophoric charge-transfer absorption band in their poled thin films. It is thus indicated that the nontrivial intermolecular interaction in solid state can vary the reaction field that acts on the chromophores in poled and depoled films, and significantly affect their achievable electro-optic (EO) activities. As a result, the guest–host polymers containing 10 wt% of chromophores in PMMA showed EO coefficients of ∼80 pm V−1 for 1/PMMA and 2/PMMA, while dramatically dropping to 20 pm V−1 for 3/PMMA. These systematic analyses led to the rational design of a new guest–host EO polymer incorporating 35 wt% of a spatially modified chromophore AJLZ55, which gave ultrahigh EO coefficients of 218 pm V−1 at 1.31 μm.