A versatile color tuning strategy for iridium(III) and platinum(II) electrophosphors by shifting the charge-transfer states with an electron-deficient coreElectronic supplementary information (ESI) available: X-Ray crystal structures and relevant data. PL spectra at 77 K. EL spectra of OLEDs. J–V–Land efficiency–current density curves for OLED devices. CCDC reference numbers 698299 (Pt-1), 698300 (Ir-1) and 639792 (Pt-2). For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/b814507e

By fusing an electron-deficient ring system with the phenyl ring of a 2-phenylpyridine (ppy)-type ligand, a new and synthetically versatile strategy for the phosphorescence color tuning of cyclometalated iridium(III) and platinum(II) metallophosphors has been established. Two robust red electrophosphors with enhanced electron-injection/electron-transporting features were prepared by using an electron-trapping fluoren-9-one chromophore in the ligand design. The thermal, photophysical, redox and electrophosphorescent properties of these complexes are reported. These exciting results can be attributed to a switch of the metal-to-ligand charge-transfer (MLCT) character of the transition from the pyridyl groups in the traditional IrIIIor PtIIppy-type complexes to the electron-deficient ring core, and the spectral assignments corroborate well with the electrochemical data as well as the time-dependent density functional theory (TD-DFT) calculations. The electron-withdrawing character of the fused ring results in much more stable MLCT states, inducing a substantial red-shift of the triplet emission energy from yellow to red for the IrIIIcomplex and even green to red for the PtIIcounterpart. Electrophosphorescent organic light-emitting devices (OLEDs) doped with these red emitters fabricated by using vacuum evaporation technique have been realized with reasonable performance. [ABSTRACT FROM AUTHOR]