Aggregation-Induced Fluorescence of Carbazole and o-Carborane Based Organic Fluorophore

Abstract

Carbazole based fluorophores 9-butyl-3,6-bis-(phenylethynyl)-9H-carbazole (1) and 9-butyl-3,6-bis-(2-phenyl-o-carborane)-9H-carbazole (2) were synthesized via Sonogashira type cross-coupling reaction and followed by insertion with decaborane. Compound 1 exhibited far more intense fluorescence than 2 in THF solution, while in solid state 2 exerted stronger fluorescence than 1. The fluorescence quenching behavior of 2 in THF solution could be attributed to the intramolecular charge transfer of donor-acceptor system in 2, which was confirmed by electrochemical experiments and DFT calculations. The fluorescence enhancement of 2 in solid state can be ascribed to aggregational induced packing which was evidenced by crystallographic study. In addition, compound 2 showed typical aggregation induced emission (AIE) behavior.

Protonation-induced fluorescence modulation of carbazole-based emitters

“…In contrast to solution, the fluorescence quantum yield of L3 and L4 increases in solid state and L4 experiences a remarkable increase from 1% to 49% in the protonated form. 35,36 The bathochromic shift of the fluorescence maxima observed for all the protonated ligands (Fig. 6) in the solid state suggests J-type packing for these compounds.…”

“…However, in solid-state, protonation enhanced fluorescence quantum yield of all the compounds increasing the fluorescence quantum yield of L4 from 1% to a noteworthy 49%. 35,36 We envision this strategy to further enhance the development of purely organic emitter materials.…”

Synthetic Supramolecular Host for D‐(−)‐Ribose: Ratiometric Fluorescence Response via Multivalent Lectin‐Carbohydrate Interactions

“…[18] Also, carbazole based probes are known for their superior electron donating as well as charge transporting characteristics. [19] Meanwhile, a wide variety of π-conjugated carbazole-based fluorophores can be synthesized by functionalization at either nitrogen end or its 3-and 6-positions. [20] Considering such structural diversity, carbazoles have often been regarded as important scaffolds for the construction of supramolecular assembly of πfunctional materials.…”

Synthesis and Structure of an o‐Carboranyl‐Substituted Three‐Coordinate Borane Radical Anion

“…[77][78][79][80][81][82][83] The ortho-isomer is a rotation-dependent π-acceptor, accepting electron density into its C1À C2 σ*-anti-bonding orbital, often leading to aggregation-induced emission (AIE). [84][85][86][87][88][89][90][91][92][93][94][95][96][97][98] Both aspects provide opportunities for novel material design. Closerange conjugation of a carboranyl moiety to a 3-coordinate boron has rarely been studied.…”

“…They are unique building blocks in optoelectronic materials with high thermal stability due to their 3‐dimensional aromaticity [77–83] . The ortho ‐isomer is a rotation‐dependent π ‐acceptor, accepting electron density into its C1−C2 σ *‐anti‐bonding orbital, often leading to aggregation‐induced emission (AIE) [84–98] . Both aspects provide opportunities for novel material design.…”