Developing new organic chromophores with a large electro-optic coefficient (r₃₃) is highly desirable for fabricating electro-optic (EO) materials. Building on the fact that the 1,1,7,7-tetramethyl julolidine fused furan ring is a good electron donor and lengthening the π-bridge of a chromophore with a five-membered heterocycle ring could lead to the improvement of r₃₃. Here we design and synthesize two new chromophores C1 and C2 by using a 1,1,7,7-tetramethyl julolidine fused furan ring as the electron donor and 2-(3-cyano-4,5,5-trimethyl-5H-furan-2-ylidene)-malonitrile (TCF) as the acceptor, but with two different π-bridges (furan-vinylene and thiophene-vinylene accordingly). When doping C1 or C2 into PMMA with a loading density of 20 wt%, the poled films containing C1 or C2 exhibited an r₃₃ value of 75 pm V⁻¹ and 94 pm V⁻¹, respectively. When compared with chromophore C3 (an ene unit as the π-bridge, r₃₃ = 52 pm V⁻¹), an enhanced r₃₃ of C1 and C2 was achieved due to the introduction of a heterocycle ring into the π-bridge. This work uncovers the influence of the heterocycle ring on the julolidine fused furan based chromophore's physical and chemical properties and demonstrates that the new chromophores are a promising candidate for EO material application.

中文翻译：

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通过引入杂环以实现高电光活性，优化基于1,1,7,7-四甲基甲氧吡啶的呋喃基生色团的分子结构†

为了制造电光（EO）材料，非常需要开发具有大的电光系数（r ₃₃）的新有机发色团。基于1,1,7,7-四甲基甲氧嘧啶稠合的呋喃环是一个良好的电子供体，延长具有五元杂环的发色团的π桥可以延长r ₃₃。在这里，我们设计和合成两个新的生色团C1和C2，使用1,1,7,7-四甲基甲氧嘧啶稠合的呋喃环作为电子供体和2-（3-氰基-4,5,5-三甲基-5 H-呋喃-2-亚烷基）-丙二腈（TCF）作为受体，但具有两个不同的π-桥（相应地有呋喃-亚乙烯基和噻吩-亚乙烯基）。当以20重量％的负载密度将C1或C2掺杂到PMMA中时，包含C1或C2的极化膜的r ₃₃值分别显示为75 pm V ^-1和94 pm V ^-1。当与发色团相比，C3（一个烯单元作为π桥，- [R ₃₃ = 52点V ^-1），增强- [R ₃₃的C1和C2由于在π-桥中引入了杂环，从而实现了这一点。这项工作揭示了杂环对基于聚吡啶的呋喃核苷的生色团的物理和化学性质的影响，并证明了新的生色团是EO材料应用的有前途的候选者。