The Importance of Polymorphism Dependent Aggregation Induced Enhanced Emission of the Acrylonitrile Derivative: Helical J Type and Antiparallel H Type Stacking Modes

Abstract

In this study to analyze the structure-property relationship of synthesized π-conjugated acrylonitrile derivative in terms of polymorphism dependent emission and conformational polymorphism, single crystal x-ray diffraction method, photophysical and theoretical studies were performed. The fluorescent molecule with two polymorphic structure were presented to demonstrate the effect of the molecular conformation and stacking type on the polymorphism dependent emission in aggregate state. According to results of crystallography and photophysical studies, both form of the molecule displayed aggregation induced enhanced emission (AIEE) property in the solid phase due to the restricted intramolecular rotation (RIR) and favourable stacking interactions including the antiparallel H type, J type stacking modes and intramolecular charge transfer (ICT) process. As a result, J type and antiparallel H type stacking mode with the restricted intramolecular rotation make the crystals higly emissive in solid phase. We believe that, studied two polymorphs will be best candidates for the π-conjugated acrylonitrile derivatives in the optoelectronic field. Moreover, this study will provide an overview of the importance of conformational polymorphism, stacking type on fluorescence properties of the polymorphic structures and propose new ways for targeted polymorphic molecular design strategies in acrylonitrile derivatives.