Strong Circularly Polarized Luminescence from Highly Emissive Terbium Complexes in Aqueous Solution

AbstractTwo luminescent terbium(III) complexes have been prepared from chiral ligands containing 2‐hydroxyisophthalamide (IAM) antenna chromophores and their non‐polarized and circularly‐polarized luminescence properties have been studied. These tetradentate ligands, which form 2:1 ligand/TbIII complexes, utilize diaminocyclohexane (cyLI) and diphenylethylenediamine (dpenLI) backbones, which we reasoned would impart conformational rigidity and result in TbIII complexes that display both large luminescence quantum yield (Φ) values and strong circularly polarized luminescence (CPL) activities. Both TbIII complexes are highly emissive, with Φ values of 0.32 (dpenLI‐Tb) and 0.60 (cyLI‐Tb). Luminescence lifetime measurements in H2O and D2O indicate that while cyLI‐Tb exists as a single species in solution, dpenLI‐Tb exists as two species: a monohydrate complex with one H2O molecule directly bound to the TbIII ion and a complex with no water molecules in the inner coordination sphere. Both cyLI‐Tb and dpenLI‐Tb display increased CPL activity compared to previously reported TbIII complexes made with chiral IAM ligands. The CPL measurements also provide additional confirmation of the presence of a single emissive species in solution in the case of cyLI‐Tb, and multiple emissive species in the case of dpenLI‐Tb.