Unveiling the structure-property relationship of X-shaped pyrazine-based D-A type luminophores with tunable aggregation-induced emission

Abstract

Tetraphenylpyrazine is an attractive species that has received intense research interests for its notable aggregation-induced emission (AIE) properties. Herein, we present elaborate syntheses of pyrazine derivatives with pendant donor-acceptor groups using modular approach. Their photophysical properties, thermal stability, and electrochemical behaviours are thoroughly investigated. Both the acidochromic and solvatochromic behaviour caused dynamic shifts in their absorption and emission spectra, providing evidence for intramolecular charge-transfer manifested by either bathochromic or hypsochromic shifts. Solvatochromic studies revealed that 3d and 3e exhibit dual emission. Investigation of fluorescence response profiles showed that 3a, 3b and 3f display aggregation-induced emission (AIE) behaviour, 3c, 3d and 3g exhibit aggregation-enhanced emission (AEE), while 3e is emissive in solution but quenched in the solid state. Restricted intramolecular rotation is the key factor deciding the AIE effect and the difference in their optical properties can be ascribed to the substituent effects. This work provides useful structure-property relationship insights for the further development of efficient luminescent materials and sensors.