Deep‐blue Fluorophores Based on Phenanthroimidazole Integrated with Benzo[d]thiazole: Experimental and Theoretical Investigation

Abstract

Three deep-blue emissive donor-acceptor (DÀ A) fluorophores, 2-(4'-(1-(4-(tert-butyl)phenyl)-1H-phenanthro [9,10-d] 10d]imidazol-1-yl)benzonitrile (m-CNPISN) based on benzothiazole with varying substituents at N1-position to tune the properties of the materials were designed and synthesized. The synthesized fluorophores were structurally confirmed by spectroscopic techniques. All the fluorophores exhibited good thermal properties with high thermal degradation temperatures. An optical study reveals that the fluorophores are capable of emitting in the blue spectral region in solution and solid. The quantum chemical investigations were also performed with the aim to understand the electronic structures of the fluorophores. Further, solution-processed OLED device was fabricated by using PTPISN as an emissive dopant and found that bright deep-blue electroluminescence with CIEy of (∼ 0.08). These results suggest that the introduction of benzothiazole moiety is a promising design strategy for obtaining new deep-blue emitters.

Design, Synthesis and Evaluation of Fluorescent Properties of Benzothiazole Derivatives

“…Our group identified some thiadiazole derivatives with inhibitory activities and fluorescence properties [32–34] . In recent years, it has been found that benzothiazole π‐conjugated moiety exhibits good photophysical properties and has attracted wide interest of researchers [35–36] . The novel pyrido[2,1‐ b ] benzothiazole derivatives 15 a – 15 d (shown in Figure 1) exhibited remarkable fluorescence intensity with considerably high quantum yields with anti‐bacterial and anti‐fungal activities [37] .…”

“…[32][33][34] In recent years, it has been found that benzothiazole πconjugated moiety exhibits good photophysical properties and has attracted wide interest of researchers. [35][36] The novel pyrido[2,1-b] benzothiazole derivatives 15 a-15 d (shown in Figure 1) exhibited remarkable fluorescence intensity with considerably high quantum yields with anti-bacterial and antifungal activities. [37] In 2020, a new fluorescent probe 2 based on conjugated benzothiazole (shown in Figure 1)showed high selectivity toward SO 3 2À /HSO 3 À in aqueous solution and achieved cells imaging.…”

An efficient blue electro-fluorescence material with high electron and balanced carrier mobilities based on effective π-stacking between acceptors

“…On the one hand, the introduction of materials with excellent electron transfer properties, such as triazole, 6,7 oxazole 8,9 etc ., is an effective way to improve the electron transfer ability. On the other hand, constructing blue emitters with a donor–acceptor (D–A) structure can provide molecular bipolarity to balance carrier transport, 10–12 and matching the energy levels of the luminescent layer with those of adjacent functional layers is also a key step to achieve balanced charge transmission. Additionally, effective π-stacking in molecules is of great importance to increase intermolecular interactions and accelerate charge transfer.…”

Highly efficient deep-blue organic light-emitting diodes (OLEDs) based on hot-exciton materials with multiple triplet exciton conversion channels

“…In recent years, many deep-blue fluorescent emitters based on hot-excitons have been reported. In order to regulate the balance between the LE state and charge transfer (CT) excited state to improve Φ PL and η r , while ensuring short wavelength emission, mild chromophore units such as phenanthroimidazoles, 12–15 carbazoles, 16–20 and triphenylamines 21–25 are usually chosen to construct hot-exciton deep-blue materials. Anthracene has a subtle energy level arrangement with a large T 1 –T 2 energy gap, which is very favorable for the hRISC process.…”