The development of mechanoluminescence from organic compounds: breakthrough and deep insight

Abstract

The organic mechanoluminescence (ML) happens at the crack surface under force, and the ML composition is becoming more complicated, extending from the normal fluorescence to phosphorescence, persistent room temperature phosphorescence and the photo-sensitive ML.

Organic luminescent materials: The concentration on aggregates from aggregation‐induced emission

“…With time going on, it was found that not all emission phenomena can be explained by molecular structure, especially for the polymorphisms with different emissive properties. [21] On the other hand, AIE was a typical F I G U R E 1 (A) The molecular structure, packing, and aggregation-caused quenching (ACQ) behavior of perylene; [1] (B) the molecular structure, packing, and aggregation-induced emission (AIE) behavior of HPS; [1] (C) the expanded AIE family based on the mechanisms of restriction of intramolecular rotation and vibration [10][11][12][13][14][15] F I G U R E 2 Some typical luminescent behaviors in aggregate heavily related to aggregation-induced emission (AIE) [22][23][24][25][26][27] solid state luminescence behavior, and the main origin for the transition from ACQ to AIE was also the changed molecular packing from intense π-π stacking to the suppressed one. Thus, scientists began to turn their attention from molecular structure to molecular packing.…”

“…On the other hand, the research of some other solid state luminescence behaviors that were derived from or parallel to AIE were carried out, such as aggregation-induced delayed fluorescence (AIDF), room temperature phosphorescence (RTP), mechanoluminescence (ML), nonaromatic fluorescence, and phosphorescence, through-space conjugation (TSC) and so on ( Figure 2). [22][23][24][25][26][27] For almost all of them, heavily packing-dependent emission could be observed, showing the interesting "Molecular Uniting Set Identified Characteristic (MUSIC)"-the evolution from a single molecule to a molecular aggregate, similar to real music in our lives: Basic atoms correspond to notes, and a melody with alignment of notes is similar to molecules constructed by atoms with specific sequences. Correspondingly, the MUSICs, which are heavily dependent on the aggregated states with various packing modes, resemble a symphony with the coming together of music produced by different instruments.…”

“…Some typical luminescent behaviors in aggregate heavily related to aggregation‐induced emission (AIE) [ 22–27 ] …”

Diversifying the luminescence of phenanthro-diimine ligands in zinc complexes

“…Organic platforms, which offer a range of molecular materials with versatile solid-state photophysical behavior without tedious synthetic modifications, are particularly attractive systems for the development of tunable and stimuli-responsive luminophores. [1][2][3][4][5][6][7][8] An efficient and straightforward approach to influence the electronic structures of π-conjugated chromophores and to modulate intermolecular interactions is the employment of coordination bonding. In this respect, readily available Zn(II) salts are considered as attractive and inexpensive modifiers of organic emitters decorated with nitrogen and oxygen donor functions.…”

Linking triptycene to silole: a fruitful association

“…[10][11][12][13][14] Moreover, with the growing number of AIE materials described in the literature, rather new and uncommon phenomena such as reversible mechanofluorochromism have started to be reported since their first observation with tetraphenylethene (TPE) and diphenyldibenzofulvene (DPDBF) derivatives. [15][16][17][18][19][20] In small molecules-based organic electronics, besides the device efficiency, the thermal and structural stabilities of the used organic materials are an important concern. 21,22 Indeed, for instance, an operating OLED releases heat that may alter quickly its efficiency.…”