Theoretical investigation on green emitting heteroleptic cyclometalated iridium(III) complexes with fluorinated 2-phenylpyridine ligands

In this work, we studied the geometrical structures, optical properties, UV-vis spectra and phosphorescence properties of three cyclometalated heteroleptic iridium complexes : (ppy-tfm)(2)Ir(pico) (Ir1), (dFppy- tfm)(2)Ir(pico) (Ir2), and (tFppy- tfm)(2)Ir(pico) (Ir3) with tfm = trifluoromethyl and pico = picolinate, dF = difluoro and tF = trifluoro by mean DFT and TD-DFT methods. Di- and tri-fluorination substitutions on phenyl rings of ppy ligands affect the metal-ligand bonds, decrease the HOMO energies of the studied complexes and increase the energy gaps. The weak and intense observed bands have been assigned in term of natural transition orbitals. Phosphorescence wavelengths were calculated according to vertical and adiabatic procedures. Simulated phosphorescence spectra agree finely with the experimental ones. Main normal modes contributing to the intense band were identified in term of shift vector.