Dual phosphorescent emissions from conformers of iridium complex rotors

Abstract

The chiral iridium rotors Ir(ppy)₂(pyX)Cl (X = CC–SiR₃, R = alkyl) remarkably contain two distinct rotational conformers in the ground (S₀) and excited (T₁) states that can be detected by NMR and emission measurements respectively at variable temperatures. The observed phosphorescent emissions, vibronic (involving L = ppy) and broad (L = pyX), arise from different triplet ligand to metal charge transfers from the two rotational conformers at distinct ³MLCT excited states. Both conformers exist in these Ir(ppy)₂(pyX)Cl rotors due to the electron-withdrawing, conjugated substituent X.