Probing the Aggregation and Signaling Behavior ofSome Twisted 99′-Bianthryl Derivatives: Observation of Aggregation-InducedBlue-Shifted Emission

摘要

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 tothis, potential of these systems toward signaling of nitroaromaticexplosive has also been explored. Among all of the nitroaromatics,the highest fluorescence quenching is observed for nitrophenols (saypicric acid (PA)). The investigation also reveals that compared tomonoaryl systems, biaryl systems are more responsive to fluorescencequenching by nitroaromatics. Perrin’s model of quenching sphereaction has been attributed to nitrophenol (PA) selective signalingbehavior of biaryl systems.