Benzannulation via the use of 1,2,4-triazines extends aromatic system of cyclometallated Pt(II) complexes to achieve candle light electroluminescence

This work describes an application of 1,2,4-triazine methodology for the synthesis of novel cyclometallated Pt (II) complexes of C^N type. It is shown that addition of a cyclopenteno unit into the complex structure not only facilitates the fabrication of efficient solution-processed OLED devices (EQE_max = 10.7%), but also imposes structural changes leading to even more soluble derivatives. Finally, it was shown that by varying the number of fused benzene rings in the C^N ligand it is possible to tune the emission from green-blueish (Φ_PL = 0.15–0.43) to yellow-orange (Φ_PL = 0.25). 1,2,4-Triazine methodology gives unique opportunity to fuse additional benzene ring into the pyridine ring and provided the ligand L5 that contained previously unexplored large aromatic system. It was shown that such benzannulation is an effective way to achieve redshift in emission and give rise to solution-processable, single dopant OLED device showing emission spectrum resembling candle light.