Nonaromatic Lysine Supramolecular Nanotube Assemblies with Excitation-Dependent Circularly Polarized Phosphorescence
Wenchao Hao, Yuan Wang, Minghua Liu
Abstract
Nonaromatic phosphorescence has burgeoned into a new frontier of luminescent materials. Herein, nonaromatic chiral lysine amphiphiles with long alkyl chains connected via urea or amide bonds are designed, and their self-assembly as well as chiroptical properties are investigated. The C18 derivative with a urea bond self-assembles into a nanotube and shows an excitation-dependent (ExD) circularly polarized phosphorescence (CPP). Under varied excitations, the CPP can be tuned from violet to blue, with a lifetime up to 32.0 ms, a quantum yield of 63.0%, and a dissymmetry factor of 5.4 × 10 –3 . In comparison, the amide bonded derivative self-assembles into a microfiber showing conventional CPP. It is suggested that the multiple noncovalent bonded clustering of the amphiphilic molecules is responsible for the CPP. Moreover, when fluorescent dyes are doped, circularly polarized luminescence with longer lifetime is obtained. The work demonstrates that self-assembled gel materials of nonaromatic chiral amphiphiles can show ExD-CPP, which opens the scope of CPP materials.