有机荧光分子2-氰基-3-(3, 4-二甲氧基苯基)-2-丙烯酰胺的可逆压致变色和质子刺激响应性能

设计合成了3-芳基-2-腈基丙烯酰胺类有机发光小分子2-氰基-3-(3, 4-二甲氧基苯基)-2-丙烯酰胺(CDMPA)。经研究发现, CDMPA化合物具有明显的压致变色和酸致变色现象。在外力刺激下,化合物CDMPA荧光最大发射峰发生20 nm的红移,经过加热或蒸汽处理后可恢复初始状态。对样品研磨前后粉末的X射线衍射图谱及荧光寿命衰减曲线进行测试分析得出, CDMPA压致变色现象归因于分子构型由晶态到无定形态的转化。另外,在酸刺激下CDMPA发光颜色由蓝光红移至黄光,最大发射波长红移33 nm。经过二甲基甲酰胺(DMF)处理后可恢复到初始状态。由测试得到的红外光谱及分子轨道理论计算推测,酸致变色现象是由氨基取代基的质子化影响了CDMPA前线分子轨道引起的。本研究可使人们深入了解这种类型材料的多刺激响应发光机制,且显著的颜色变化性能使CDMPA在传感器和检测装置方面具有潜在的应用前景。

Reversible Piezochromism and Protonation Stimuli-Response of (Z)-2-Cyano-3-(3,4-dimethoxyphenyl)acrylamide

A 3-aryl-2-cyano acrylamide derivative (Z)-2-cyano-3-(3, 4-dimethoxy-phenyl)acrylamide (CDMPA) was designed and synthesized, which exhibited piezochromism and acidchromism properties. Under external mechanical force stimuli, CDMPA showed a red-shift of 20 nm in its fluorescence emission and the mechanically induced luminescence color could return to the original state via heating or solvent vapor treatment. Powder X-ray diffraction (XRD) and fluorescence lifetime experiments indicated that the piezochromic luminescence could be attributed to the transformation from the crystalline to the amorphous phase. Additionally, the fluorescence color changed from blue to yellow with a red-shift of 33 nm using the stimulus of protonation. The emission color was recovered upon fuming with dimethyl formamide (DMF) vapor. Infrared (IR) spectra of CDMPA powder and theoretical calculation of the frontier molecular orbitals showed that protonation of the amino moieties in CDMPA had a significant effect on the frontier molecular orbitals and, thus, caused the acidchromism phenomenon. This study provides comprehensive insight into the stimuli-responsive luminescent mechanisms within this type of compound and the reversible switching of emission color may enable discovery of novel applications of CDMPA for detection and sensing devices.