High‐Contrast Polymorphic Luminogen Formed through Effect of Tiny Differences in Intermolecular Interactions on the Intramolecular Charge Transfer Process

Abstract

Polymorphic luminogens provide the opportunity to disclose relation between the packing patterns and performance of luminogen and facilitate design of high performance luminogens. However, the effect of intramolecular charge transfer (ICT) is seldom used to construct luminogens with polymorphs, though the ICT process is very sensitive to microenvironment. In this work, 2‐(3‐(diphenylamino)‐9H‐xanthen‐9‐ylidene)‐malononitrile (DPAXM, 1) with donor–acceptor structure exhibits high contrast polymorphism dependent emission due to the effect of tiny differences of intermolecular interactions on ICT process. Three crystals of 1 with nearly identical structures emit yellow, orange, and red light with sequentially decreased efficiency which is attributed to ICT process modulated by the tiny differences in intermolecular interactions. In addition to ground state study, excited state of the polymorphs is investigated by time‐resolved ultrafast transient mid‐IR spectroscopy and theoretical calculation. Nonemissive crystals of 1 can also be obtained. The modulation of ICT effect by intermolecular interactions may provide a reference for the molecular design of high‐performance luminogens.

A multifunctional luminescent material based on quinoxaline and triphenylamine groups: polymorphism, mechanochromic luminescence, and applications in high-efficiency fluorescent OLEDs

“…When the doping concentration is increased to 20 wt%, device D2 displays the best performance with maximum CE, PE, and EQE values of 17.1 cd A −1 , 16.3 lm W −1 , and 6.0%, breaking the 5% EQE limit for traditional fluorescent materials and disproving the statement that MCL materials possess poor EL performance due to their inherently loose molecular structures. 25,38 Upon further increasing the doping concentration to 30 wt%, the CE, PE, and EQE decreased to 14.9 cd A −1 , 13.0 lm W −1 , and 4.3%, respectively. The non-doped device achieves high performance, with a maximum luminance of 9709 cd m −2 , EQE of 5.2%, CE of 14.91 cd A −1 , and PE of 14.19 lm W −1 , exceeding the theoretical EQE limit of 5% for traditional fluorescent emitters.…”

Design of Stimuli‐Responsive Phenothiazine Derivatives with Triplet‐Related Dual Emission and High‐Contrast Mechanochromism Guided by Polymorph Prediction

“…Clearly, tiny differences of intermolecular interactions would significantly affect the charge transfer process, further affect their emission properties. [16] Concentration-dependent elec-tronic absorption spectra of P1 in toluene manifested that a small absorption tail around 420 nm appeared with the increase of the concentration (Figure S9). This band could be assigned to the intermolecular charge transfer absorption band, probably due to the formation of aggregates through intermolecular interactions.…”

Phenothiazine-Based Luminophores with AIE, Solvatochromism, and Mechanochromic Characteristics

“…AIEgens usually have a highly distorted molecular conformation coupled with a loose molecular stacking, making it an important candidate for a luminescent material that responds to mechanical force. , To evaluate the MC luminescence properties of two molecules, the fluorescence behaviors under different solid-state conditions were studied. As shown in Figure a,c, the pristine DPE-PTZ-Cl sample exhibited blue fluorescence with an emission peak at 462 nm.…”