Tracking of tuning effects in bis-cyclometalated iridium complexes: a combined time resolved infrared spectroscopy, electrochemical, and computational study.

Electronic structure and photophysical properties have been investigated for a new series of fluorinated iridium complexes with the parent Ir(ppy)2(deeb) (deeb is 4,4'-diethylester-2,2'-bipyridine). Time resolved infrared spectroscopy (TRIR) has been used to observe the long-lived triplet excited state of each complex confirming its mixed charge transfer character. Supplementary evidence of charge transfer in the triplet state is provided via emission spectroscopy, transient absorption spectroscopy, and density functional theory (DFT) calculations. Both computational and spectroscopic assignments reveal consistency in the first excitation throughout the series of complexes. Electrochemical measurements meanwhile show that increasing fluorination still induces expected shifting of frontier orbitals. Excited states beyond the lowest lying triplet are probed for the complexes via UV-vis spectroscopy which reveals three distinct features. These features are assigned via time-dependent DFT (TD-DFT) to build a broader understanding of electronic structure.