Synthesis, Characterization, and Applications of Highly Efficient Far-Red to Near Infra-Red Emissive β-Dicyanodistyrylbenzene Derivatives

Abstract

In the last decades, the immense interest in highly fluorescent π-conjugated compounds which emit deep red to near infrared (NIR) in the solid state has been driven by their utilities toward advanced photonic applications such as organic light-emitting diodes, fluorescent chemosensors, organic solid-state lasers. However, most of organic red emitting fluorophores suffer from aggregation-caused quenching due to their characteristics of strong π–π stacking, dipole-dipole interaction or donor (D)-acceptor (A) charge transfer interaction. Thus, the development of strongly far-red to NIR emitting materials in the solid state is still challenging. Recently, highly fluorescent solid-state emitters based on 2Z,2'Z-3,3'(or2,2)-(2,5-dimethoxy-1,4-phenylene)bis(2(or3)-phenylacrylonitrile (MODCS) have been explored and contributed to establish the relationship between the molecular arrangement and the corresponding fluorescence features on aggregation-induced enhanced emission (AIEE) depending on the position of the pendant cyano group on the stilbene. As an extended work for further development of β-MODCS exhibiting strong deep red-NIR fluorescence, I herein report the synthesis of the D-A-D-A-D type β-dicyanodistyrylbenzene (β-DCS) derivatives that have various N-amine moieties (β-MODEADCS, β-MODBADCS, β-MODPADCS, β-EODEADCS) with emission maximum peaks in the range of 650 nm and 718 nm. Among them, β-MODEADCS especially exhibits emission in the Near Infra-Red region with quite good quantum efficiency (ФFL = 0.42). These unique highly emissive properties in the solid-state were thoroughly investigated by UV-Vis spectroscopy, photoluminescence spectroscopy, fluorescence lifetime measurement, electrochemical measurement, and single crystal X-ray analysis. Furthermore, we also present β-dicyanodistyrylbenzene based highly red fluorescent amphiphilic molecules β-EODEADCS and β-wedge DEADCS. Their optical properties and intriguing nanostructures in water were obtained by DLS, SEM, cryo-TEM experiments and UV-Vis spectroscopy. Based on the understanding of their optoelectrical characteristics, we demonstrated p-type single crystal organic field-effect transistors (SC-OFETs) using high crystalline β-MODEADCS and bio-imaging with self-assembled nanoparticles of β-EODEADCS.