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Substituent Group Variations Directing the Molecular Packing, Electronic Structure, and Aggregation-Induced Emission Property of Isophorone Derivatives

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posted on 2013-04-05, 00:00 authored by Zheng Zheng, Zhipeng Yu, Mingdi Yang, Feng Jin, Qiong Zhang, Hongping Zhou, Jieying Wu, Yupeng Tian
A series of new isophorone derivatives (15), incorporating the heterocyclic ring or aza-crown-ether group, with large Stokes shifts (>140 nm), have been synthesized and characterized. 14 display aggregation-induced emission behaviors, while dye 5 is highly emissive in solution but quenched in the solid state. It was found that the tuning of emission color of the isophorone-based compounds in the solid state could be conveniently accomplished by changing the terminal substituent group. The photophysical properties in solution, aqueous suspension, and crystalline state, along with their relationships, are comparatively investigated. Crystallographic data of 14 indicate that the existence of multiple intermolecular hydrogen bonding interactions between the adjacent molecules restricts the intramolecular vibration and rotation and enables compounds 14 to emit intensely in the solid state. The size and growth processes of particles with different water fractions were studied using a scanning electron microscope, indicating that smaller globular nanoparticles in aqueous suspension are in favor of fluorescence emissions. The above results suggest that substituent groups have a great influence on their molecular packing, electronic structure, and aggregation-induced emission properties. In addition, fluorescence cell imaging experiment proved the potential application of 5.