Excited-State Switching in Rhenium(I) Bipyridyl Complexes with Donor–Donor and Donor–Acceptor Substituents

The optical properties of two Re(CO)3(bpy)Cl complexes in which the bpy is substituted with donor (triphenylamine, TPA, ReTPA2) as well both (TPA) and acceptor (benzothiadiazole, BTD, ReTPA-BTD) groups are presented. For ReTPA2 absorption spectra show intense intraligand charge-transfer (ILCT) bands at 460 nm small solvatochromic behavior; for ReTPA-BTD ILCT transitions weaker. These assigned TPA → supported by resonance Raman data TDDFT calculations. excited-state spectroscopy shows presence emissive states complexes. intensity these emission signals modulated solvent. Time-resolved infrared definitively assigns excited present CH2Cl2 to be MLCT nature, MeCN nature. DFT calculations indicated this switching solvent governed access controlled spin-orbit coupling, sufficiently different solvents, allowing select out each states.