Experimental and theoretical investigation of long-wavelength fluorescence emission in push–pull benzazoles: intramolecular proton transfer or charge transfer in the excited state?

Abstract

ESIPT is disfavoured and charge-transfer emission, prior to ESIPT, seems to be responsible for long-emission wavelengths.

Solvatochromism and pH effect on the emission of a triphenylimidazole-phenylacrylonitrile derivative: experimental and DFT studies

“…This behaviour has attracted considerable attention because of the charge transfer nature (intra/inter molecular); it could be used as sensors of solvent polarity as well as volatile organic compounds. 17,18 Among heteroaromatic compounds, the imidazole scaffold exhibits electron attracting or mild donating nature which displayed unique optical, thermal, electronic and biological properties. 19 Especially, 2,4,5-triphenyl-1H-imidazole, (lophine, Scheme 1), exhibited uorescence and chemiluminescence properties when reacted with oxygen in the presence of strong basic conditions.…”

LC-BLYP Calculations of the Structures and Photophysical Properties of [1,3]Thiazolo[4,5-b]pyrazine Derivatives in Cyclohexane and Methanol

“…Introducing both an EDG and an EWG to the parent compound can lead to an intramolecular charge transfer (ICT) process, yielding a large Stokes shift. [1][2][3][4][5][6]8,15 Apart from that, the solvent polarity much affects the fluorescence spectra since some solvents can promote or hinder the emission at a long wavelength. [1][2][3]5,8 Recently, 11 TPy derivatives (Figure 1) were newly designed and synthesized using different kinds of substituents and varying the number of substituents.…”

“…[1][2][3][4][5][6]8,15 Apart from that, the solvent polarity much affects the fluorescence spectra since some solvents can promote or hinder the emission at a long wavelength. [1][2][3]5,8 Recently, 11 TPy derivatives (Figure 1) were newly designed and synthesized using different kinds of substituents and varying the number of substituents. 1−3 As shown in Figure 1, PBT, TPy-1, TPy-1_NMe 2 , TPy-1_OMe, and TPy-1_CN are classified as the small-sized compounds, whereas TPy-2, TPy-3A, TPy-3B, TPy-3C, TPy-4A, TPy-4B, and TPy-4C are the medium-sized compounds.…”

“…Bioluminescence and organic fluorophores have become more attractive due to their fluorescence functions and applications in the fields of life science, analytical science, and materials science. − Some fluorophores can be applied as fluorescent probes and fluorescent sensors for tract tracing or labeling target molecules for biological imaging. − , Nowadays, the fluorescence performance of some organic compounds has been developed, and it has become one of the main subjects for the involved experimental and theoretical studies. Several scientists have paid attention to the design and synthesis of new fluorescent compounds from the naphthalene- or benzo-fused compounds such as benzothiazole (PBT) and thiazolo­[4,5- b ]­pyrazine (TPy). − ,,− …”

“…A well-known method for designing new fluorophores is introducing the substituents to the parent compound. − ,,,− The substituents with a strong electron-donating ability and the number of substituents are significant for the photophysical properties of the fluorophores. − The electron-donating group (EDG) and electron-withdrawing group (EWG) are usually used as substituents to induce the fluorescence character or to increase the fluorescence yields. − ,,,,− Furthermore, one EDG attached to a parent compound can promote the long-wavelength fluorescence emission, and two EDG can also enhance the fluorescence brightness. Introducing both an EDG and an EWG to the parent compound can lead to an intramolecular charge transfer (ICT) process, yielding a large Stokes shift. − ,, Apart from that, the solvent polarity much affects the fluorescence spectra since some solvents can promote or hinder the emission at a long wavelength. − ,, Recently, 11 TPy derivatives (Figure ) were newly designed and synthesized using different kinds of substituents and varying the number of substituents. − As shown in Figure , PBT, TPy-1, TPy-1_NMe 2 , TPy-1_OMe, and TPy-1_CN are classified as the small-sized compounds, whereas TPy-2, TPy-3A, TPy-3B, TPy-3C, TPy-4A, TPy-4B, and TPy-4C are the medium-sized compounds. Some of those compounds show high fluorescence performance such as having a redshifted maximum wavelength (λ max ) and/or increased fluorescence brightness. − …”