Supramolecular polymeric nanowires: preparation and orthogonal modification of their photophysical properties

Abstract

A series of three-dimensional shape-persistent molecules with three conjugated arms perpendicular to a planar core were developed to self-assemble into supramolecular polymeric nanowires through multiple hydrogen-bonding interactions. After introducing bulky functional groups, aggregation of the nanowires was inhibited, and single molecular nanowires were obtained in concentrated solutions. Therefore, these nanowires had large surface areas with functional groups appended on the surface. Moreover, the photophysical properties of the functional groups including emission peaks and fluorescent lifetime were not changed after self-assembly. Some nanowires emitted high fluorescence after incorporating various chromophores on the side chains of the three-dimensional skeleton through effective fluorescence resonance energy transfer. For example, 1-BTHex showed a quantum efficiency of about 7.9% in solution, similar to the model compound DHBT. However, in the solid state the fluorescence of DHBT was almost quenched with a quantum efficiency lower than 1% due to π–π interactions, but 1-BTHex also gave much higher quantum efficiency, about 6%, which was close to that in solution.