Thymine-Induced Dynamic Switching of Self-Assembled Nanofibers in Diaminotriazine-Functionalized Tetraphenylethylene Derivatives: Implications for One-Dimensional Molecular Devices.

Abstract

One-dimensional (1D) supramolecular polymers of aggregation-induced emission (AIE)-active chromophores belong to an in-demand group of functional materials because of their potential applications in optoelectronic devices like optical waveguides, lasers, displays, photodetectors, field-effect transistors, and solar cells. Herein, we report the hydrogen (H)-bondingdirected self-assembly of diaminotriazine-appended tetraphenylethylene derivatives (TPE-DAT) into 1D-fibers, hierarchical organogels and their thymine-induced structural transitions. The intermolecular H-bonding ability of diaminotriazine (−DAT═DAT−) leads to the formation of TPE dimers, which upon subsequent cooperative self-assembly via π–π stacking forms micrometer-long, blue-emissive, bundled nanofibers. Further, we exploit the molecular recognition property of thymine nucleobase toward the diaminotriazine unit to tune the properties of this 1D assembly. In the presence of a thymine derivative (T-C12), the blue-emissive, bundled nanofibers of TPE-DAT having a width of 70–80 nm changes to green-emissive nanofibers of TPE-DAT≡T-C12 with 30–40 nm width. This transition from blue- to green-emissive nanofibers and hierarchical gels was ascribed to the change in monomeric units, their molecular planarity, and packing in the self-assembly, which was further probed by UV–visible absorption, atomic force microscopy (AFM), transmission electron microscopy (TEM), and fluorescence properties. In addition, to gain more insights into the mechanism of these 1D-assemblies, we explored the self-assembly properties of chiral and racemic derivatives of TPE-DAT and the gelation properties of TPE-DAT and TPE-DAT≡T-C12. In short, this work demonstrates the use of the molecular recognition property of nucleobase and nucleobase analogues in constructing and controlling the formation of rarely reported 1D-assemblies of AIE-active TPE chromophores.