Synthesis, physical properties and OLED performance of azatetracenes

•Two new azatetracenes were synthesized and fully characterized.•The monoazatetracene showed higher fluorescence than rubrene, while diazatetracenes show very low fluorescence.•The OLED devices have been fabricated for the high fluorescent monoazatetracene dye.

Two novel azatetracenes: 5,7,8,9,10,12-hexaphenyl-2-azatetracene (2) and 1,4,6,11-tetraphenyl-2,3-diazatetracene (3), were synthesized and characterized. Comparing to Rubrene, 2 and 3 show blue-shifted absorptions. Interestingly, 2 displays stronger emission than rubrene in CH2Cl2, while the fluorescence of 3 is almost quenched. The electrochemical studies suggested that inserting sp2 N atoms into the backbone of tetracene could decrease both HOMO and LUMO orbital energies and more sp2 N atoms would result in lower HOMO orbital energy level. Since 2 has stronger fluorescence than rubrene, organic light emitting devices with 2 as emitters have been fabricated and the as-fabricated devices show a maximum current efficiency as high as 6.6 cd A−1. Our results indicated that the number of sp2 N atoms in the backbone of parent oligoacenes did have strong effect on the properties of as-resulted azaoligoacenes and this research could provide some guides to design and synthesize novel larger azaacenes.

Graphical abstractTwo novel azatetracenes have been synthesized through [4 + 2] cycloaddition reaction and shown different emission properties.Figure optionsDownload full-size imageDownload as PowerPoint slide