3,14‐Bis(p‐nitrophenyl)‐17,17‐dipentyltetrabenzo[a,c,g,i]‐fluorene: A New Fluorophore Displaying Both Remarkable Solvatochromism and Crystalline‐Induced Emission

Abstract

A series of 17,17-dialkyl-3,14-diaryltetrabenzofluorenes were efficiently prepared by using Suzuki-Miyaura cross-coupling reactions of the corresponding 3,14-dibromo derivatives. Studies of the unique fluorescence properties of these compounds showed that they display intense blue to yellow fluorescence with high quantum yields in the solution state and blue to orange fluorescence with moderate quantum yields in the solid state. In addition, the fluorescence wavelength of the bis(p-nitrophenyl) derivative is remarkably solvent-dependent in a manner that correlates with the solvent polarity parameter E(T)(30). The results of density function theory calculations suggest that the intramolecular charge-transfer character of the HOMO-LUMO transition is responsible for the large solvent effect. Moreover, addition of water to a tetrahydrofuran (THF) solution of this compound leads to quenching of the yellow fluorescence owing to an increase in the solvent polarity. However, when the amount of water fraction exceeds 70%, a new fluorescence band appears at the same orange-red emission wavelength as that of the solid-state fluorescence. This observation suggests the occurrence of a crystallization-induced emission (CIE) phenomenon in highly aqueous THF.

Revisiting the non-fluorescence of nitroaromatics: presumption versus reality

“…In contrast to 23 , dye 24 85 fluoresces predominately in solvents of low polarity, reaching the highest value of Φ f in toluene (0.37) (Fig. 13 and 14).…”

Deciphering the unusual fluorescence in weakly coupled bis-nitro-pyrrolo[3,2-b]pyrroles

“…Studies of disubstituted benzenes 29 , bis-ethynobenzenes 30 , disubstituted naphthalenes 31 , and fused nitro-fluorenes 32,33 demonstrate these design principles for organic branched fluorescent nitro-aromatics. In these examples, an increase in solvent polarity increases the fluorescence efficiency, which indicates that radiative deactivation occurs from states with a pronounced CT character 8,34 .…”

The solvatochromism and aggregation-induced enhanced emission based on triphenylamine-propenone

“…Xu et al reported a new D-p-A system OZA-SO, which also displayed the AIE phenomenon by the restriction of ICT. 29 Besides, several materials with ICT and AIE properties were reported, for example, tetrabenzofluorene derivatives, 30 dicarbazolyl triphenylethylene derivatives. 31 The investigations on the D-p-A molecules may help to reveal the intrinsic process of the fluorescence enhancement and spectral shifts in their molecular aggregates.…”