Strategic Approach to Pyrazinoquinoxaline Molecular Design for Enhanced Performance

The availability of affordable organic compounds with thermally activated delayed fluorescence (TADF) properties represents a unique class of materials for addressing key challenges in organic electronics. In this context, we have successfully designed and synthesised three novel hybrid molecules 2-(4-(3,6-di-tert-butyl-9H-carbazol-9-yl)phenyl)-3,7,8-triphenylpyrazino[2,3-g]quinoxaline (tCz-PyrQx), 4-(tert-butyl)-N-(4-(tert-butyl)phenyl)-N-(4-(3,7,8-triphenylpyrazino[2,3-g]quinoxalin-2-yl)phenyl)aniline (tDPA-PyrQx), and 2-(4-(9,9-dimethylacridin-10(9H)-yl)phenyl)-3,7,8-triphenylpyrazino[2,3-g]quinoxaline (Ac-PyrQx) comprising electron-donating 3,6-di-tert-butyl-9H-carbazole, bis(4-(tert-butyl)phenyl)amine, and (9,9-dimethyl-9,10-dihydroacridine) with electron-accepting pyrazinoquinoxaline groups. The incorporation of highly planar and rigid pyrazinoquinoxaline electron-accepting moieties holds significant importance due to their unique properties like efficient charge transfer, and reduced steric hindrance. Their planar structure facilitates strong π-π stacking interactions and efficient charge transfer within the molecular framework, leading to improved exciton formation and enhanced reverse intersystem crossing (RISC) rates, which are critical for TADF processes. The three different electron-donating groups with pyrazinoquinoxaline were synthesised with the view of tuning the photophysical and electrochemical properties of the hybrids.