This report describes the synthesis and study of two new amino-containing donor-acceptor lactone-bridged biaryls as pi-expanded, or benzannulated, coumarins based on the 6H-benzo[]chromen-6-one (benzo[]coumarin) structural unit. These fluorescent and planar compounds exhibit strong intramolecular charge transfer (ICT) through the conjugated biaryl unit via a diethylamino donor on one arene and either a nitro or cyano acceptor unit on the opposing arene. The ICT of these systems can be reversibly altered via two different stimuli: 1) addition of a strong base (hydroxide) results in nucleophilic cleavage of the lactone bridge which dramatically weakens ICT by disrupting conjugation between the individual arenes and 2) addition of a strong acid protonates the diethylamino donor unit, disrupting its ability to donate, thereby causing ICT to be attenuated. The presence of strong acid or base results in dramatic changes in optical absorption and emission properties of these systems which can be readily observed both spectroscopically and visually. Ultimately compounds containing the benzo[]coumarin structural unit with amine donors could act as three-state halochromic molecular switches and dyes.

中文翻译：

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具有内酯桥接单元的含氨基供体-受体联芳基作为三态卤色 pi 扩展香豆素

本报告描述了基于 6H-苯并[]色烯-6-酮（苯并[]香豆素）结构单元的两种新型含氨基供体-受体内酯桥联联芳基化合物的合成和研究，作为 pi 扩展或苯并环化香豆素。这些荧光平面化合物通过一个芳烃上的二乙氨基供体和相对芳烃上的硝基或氰基受体单元通过共轭联芳基单元表现出强烈的分子内电荷转移（ICT）。这些系统的 ICT 可以通过两种不同的刺激进行可逆改变：1）添加强碱（氢氧化物）会导致内酯桥发生亲核断裂，从而破坏各个芳烃之间的共轭，从而显着削弱 ICT；2）添加强碱（氢氧化物）酸使二乙氨基供体单元质子化，破坏其供体能力，从而导致 ICT 减弱。强酸或强碱的存在会导致这些系统的光学吸收和发射特性发生巨大变化，这可以通过光谱和视觉轻松观察到。最终，含有苯并[]香豆素结构单元和胺供体的化合物可以充当三态卤色分子开关和染料。