Synthesis, Photophysics, and Reverse Saturable Absorption of transBis-cyclometalated Iridium(111) Complexes (CANAC)Ir(R-tpy)(+) (tpy=2,2 ':6 ',2 ''-Terpyridine) with Broadband Excited -State Absorption

Extending the bandwidth of triplet excited-state absorption in transition-metal complexes is appealing for developing broadband reverse saturable absorbers. Targeting this goal, five bis-terdentate iridium(III) complexes (Ir1-Ir5) bearing trans-bis-cyclometalating ((CNC)-N-boolean AND-C-boolean AND) and 4'-R-2,2':6',2?-terpyridine (4'-R-tpy) ligands were synthesized. The effects of the structural variation in cyclometalating ligands and substituents at the tpy ligand on the photophysics of these complexes have been systematically explored using spectroscopic methods (i.e., UVvis absorption, emission, and transient absorption spectroscopy) and time-dependent density functional theory (TDDFT) calculations. All complexes exhibited intensely structured 1p,p* absorption bands at Ir1 > Ir5 > Ir3. The RSA trend corresponded well with the strength of the excited-state and ground-state absorption differences (?OD) at 532 nm for these complexes.