Aggregation‐Induced Emission‐Active Carbazolyl‐Modified Benzo[4,5]thiazolo[3,2‐c]oxadiazaborinines as Mechanochromic Fluorescent Materials

Abstract

Two highly emissive donor-acceptor type organoboron dyes, based on carbazole donor and benzothiazole-fused oxadiazaborinine acceptor, were designed and synthesized. The compounds demonstrated high positive solvatofluorochromism in solutions, caused by intramolecular charge transfer. Such carbazolyl-containing N,O-chelated organoboron dyes exhibited aggregation-induced emission properties: in tetrahydrofuran/ water mixture with a high water amount, they formed highly emissive nanoaggregates. Both materials demonstrated efficient solid-state emission in the crystalline and thin film state (PLQY of up to 48 %), as well as significant mechanofluorochromic properties (Δλ em = 30-38 nm). Moreover, a compound with unsubstituted carbazole unit was isolated as two distinct crystalline polymorphs with different photophysical properties.

Recent advances in the synthesis of luminescent tetra-coordinated boron compounds

“…From these results it was concluded that the cyano group plays an important role in acquiring strong ICT behavior and AIE and mechanochromic properties. Among the seven BF 2 -compounds (186)(187)(188)(189)(190)(191)(192) studied by Lu and co-workers 176 186 and 189 exhibited the AIE phenomenon and mechanochromism, respectively. In 2017, Gao et al 178…”

“…In an analogous fashion benzothiazole, pyrazoline, oxadiazole, benzimidazole, benzoxazole, thiadiazole, imidazole, thiazole, imidazole-pyridine and phenanthroimidazole based B-N coordinated tetra-coordinated boron compounds were synthesized and studied for their optical properties. [170][171][172][173][174][175][176][177][178][179][180][181][182][183][184][185][186][187][188][189] Among the different boron-compounds reported: 180, 181, 188 184, 185, 177 186-192, 176 and 193 178 (Fig. 20) exhibited aggregation induced emission (AIE) and reversible mechanochromic properties.…”