Self-Assembly Solid-State Enhanced Red Emission of Quinolinemalononitrile: Optical Waveguides and Stimuli Response

Abstract

The fluorescence of luminescent emitters is often quenched in the solid state, because of the typical aggregation-caused quenching (ACQ) effect, which is a thorny obstacle to high-performance organic optoelectronic materials. The exploration of solid-state enhanced long wavelength, red-emitting chromophores, especially possessing one-dimensional (1D) assembly features, is of great importance. Interestingly, an excellent solid-state enhanced red emission system (denoted as ED) based on quinolinemalononitrile has been developed via the delicate modification of the conventional ACQ dicyanomethylene-4H-pyran (DCM) derivative (denoted as BD) through crystal engineering. ED exhibits extraordinary self-assembly property in a variety of solvents, even realizing the "waving ribbons" with a length of 6 mm and a diameter of 10 μm. Crystal analysis shows that the CH···π and CH···N supramolecular interactions of ED contribute to the twisted self-assembly solid-state enhanced emission phenomenon. However, for BD, strong face-to-face stacking leads to fluorescence quenching in the solid state. Because of such easy assembly and strong solid-state emission properties, application for optical waveguides of ED is realized with a low optical loss. Stimuli-responsive behavior is also elaborated with color change between orange and red by grinding/fuming or pressing/heating.

Optical properties of amphiphilic copolymer-based self-assemblies

“…The resulted H-aggregation absorption spectra are blue shifted against the solution and exhibit low radiative rate constants k r due to the dipole-forbidden nature of the emitting state. H-aggregation may result in the aggregation-induced quenching (AIQ) effect, which is a thorny obstacle to high performance organic optoelectronic materials [66]. On the other hand, J-aggregation displays larger molecular displacement along the long molecular axis with higher k r which usually induces a red shifted absorption spectrum and the formation of an aggregation-induced emission enhancement (AIEE) system [67,68].…”

Tuning solid-state emission properties of pyrene-containing chalcone derivatives

“…5,9 However, the design of efficient organic fluorophores remains challenging since the chemical structure and the electronic properties of the individual molecules, although they are important factors in solution phase, do not allow reliable prediction of the emission behavior in the condensed phase. For instance, molecular assembly can lead to Jor H-aggregates that produce emissive or poorly emissive structures, respectively.…”

Morphology directing synthesis of 1-aminopyrene microstructures and its super quenching effect towards nitro aromatics

“…The extent of staking i.e. overlap of π orbitals become more and more until it reaches the thermodynamically stable larger crystal structures and it is responsible for red shift of emission band with increasing size of the aggregated structures within the hydrosol [49].…”