A series of novel 3,6-diamino-7,8-dihydroisoquinoline-4-carbonitrile (DDIC) derivatives were prepared from dicyanomethylene-4H-pyran derivatives and secondary amines by a mechanism of ring-opening and sequential ring-closing reactions. This reaction had the advantages of readily available materials, simple operations, mild reaction conditions, a broad substrate scope, and good yields. The DDIC derivatives displayed solid-state fluorescence with the emission wavelengths covering the whole visible light range, and the solid-state emissions were demonstrated to be ascribed to the twisted molecular conformations and loose stacking modes by crystal structural analyses. Among the compounds, 9aa exhibited a bathochromic mechanofluorochromic (MFC) phenomenon from blue to cyan due to increased molecular conjugation upon grinding, whereas 3aj and 3ka exhibited hypsochromic MFC activities with the color changing from orange to green and red to orange, respectively, because of decreased molecular conjugation, revealing that full-color-tunable emissions could also be realized by mechanofluorochromism. Furthermore, MFC-active molecules can be used in the field of encryption of important image or text information. Additionally, 3ka was demonstrated to emit single-molecular white fluorescence in organic solvents through the regulation of the concentration. The unexpected discovery of the DDIC derivatives provides a new possibility for the design and synthesis of novel isoquinoline-based fluorescent materials with excellent performance in the solid state.

中文翻译：

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3,6-二氨基-7,8-二氢异喹啉-4-腈衍生物：意想不到的简便合成，全色可调固态发射和机械变色活性

由二氰基亚甲基-4 H-吡喃衍生物和仲胺通过开环和顺序的闭环反应机理制备了一系列新颖的3,6-二氨基-7,8-二氢异喹啉-4-腈（DDIC）衍生物。该反应的优点是材料容易获得，操作简单，反应条件温和，底物范围宽和产率高。DDIC衍生物显示出固态荧光，其发射波长覆盖整个可见光范围，并且通过晶体结构分析证明固态发射归因于扭曲的分子构象和松散的堆积模式。在化合物中，9aa由于研磨过程中分子的共轭增加，从蓝到青呈现出红色的机械变色（MFC）现象，而3aj和3ka则表现出变色的MFC活性，其颜色从橙色变为绿色，从红色变为橙色，这是由于分子结合减少所致。通过机械荧光致变色也可以实现全色可调发射。此外，MFC活性分子可用于重要图像或文本信息的加密领域。另外，3ka已证明通过调节浓度可在有机溶剂中发出单分子白色荧光。DDIC衍生物的意外发现为固态性能优异的新型基于异喹啉的荧光材料的设计和合成提供了新的可能性。