Probing the Aggregation and Signaling Behavior of Some Twisted 9,9′-Bianthryl Derivatives: Observation of Aggregation-Induced Blue-Shifted Emission

Abstract

With an aim to understand the photophysical behavior of twisted organic fluorescent molecules in their aggregated state, two twisted biaryl molecules, namely, 9,9′-bianthryl and 10,10′-dicyano-9,9′-bianthryl, have been synthesized and characterized by conventional spectroscopic methods. To understand the role of C–C bond twisting on the photophysical response of biaryl aggregates, monoaryl counterparts (anthracene and 9-anthracenecarbonitrile) of the biaryl systems are also investigated. Photophysical behaviors of these systems along with their monoaryl counterpart are investigated in both solution and aggregated state. Investigations reveal that fluorescence spectra of the biaryl compounds show blue-shifted emission upon aggregation. Interestingly, no blue shift of the emission has been observed for monoaryl aggregates. Photophysical data of biaryl systems compared to monoaryl unit reveal that change in geometry, during self-assembly process, disfavors the formation of charge-transfer state, which eventually causes blue shift in the emission upon aggregation. In addition to this, potential of these systems toward signaling of nitroaromatic explosive has also been explored. Among all of the nitroaromatics, the highest fluorescence quenching is observed for nitrophenols (say picric acid (PA)). The investigation also reveals that compared to monoaryl systems, biaryl systems are more responsive to fluorescence quenching by nitroaromatics. Perrin’s model of quenching sphere action has been attributed to nitrophenol (PA) selective signaling behavior of biaryl systems.

Photophysical Characteristics of Polarity‐Sensitive and Lipid Droplet‐Specific Phenylbenzothiadiazoles

“…The solvatochromic behavior was more modest with strong EWGs ( 8 – 10 ), except in aqueous environment. By contrast, 1 – 3 showed blue‐shifted emission in PBS buffer, further supporting our aggregation hypothesis [11j,p,15] . Compound 1 exhibits a unique behavior in the series: its fluorescence quantum yield gradually decreased with increased solvent polarity, and the emission efficiency was entirely quenched in DMSO, methanol and PBS solution (Φ F ≤0.01).…”

Photophysical Properties of Benzophenone Based TADF Emitters in Relation to Their Molecular Structure

“…From the results, it can be deduced that compounds with more rigid electron donating groups such as PXZ, PTZ and DMAC, possess a broadened band (~350-500 nm) appearing after the high intensity LE band (~300 nm), which can be ascribed to the presence of CT states. [63][64][65] Nevertheless, the reasonably rigid emitters of Group 4 also have blue-shifted absorption spectra, which is most likely due to the less efficient nature of the specific D-A type architecture. Indeed, the presence of a unique donor unit might be decreasing the CT character of the electronic transitions, coherently reduced T1-S1 upconversion efficiency has been previously reported for some D-A type emitters.…”

Facile approach to benzo[d]imidazole-pyrrolo[1,2-a]pyrazine hybrid structures through double cyclodehydration and aromatization and their unique optical properties with blue emission

“…The observed blue shi was interesting since a bathochromic shi in the aggregated state is more common. 35 With the addition of DMSO stock to water during sonication, moderately uniform nanoparticles were formed with a diameter of 198 nm (Fig. 5).…”