Structural relaxation chirality transfer enhanced circularly polarized luminescence in heteronuclear Ce^III–Mn^II complexes

Circularly polarized luminescence (CPL) materials have developed rapidly in recent years due to their wide application prospects in fields like 3D displays and anti-counterfeiting. Utilizing energy transfer processes to transfer chirality has been proven as an efficient way to obtain CPL materials. However, the physics behind energy-transfer induced CPL is still not clear. Herein, in a well-designed heteronuclear Ce^III-Mn^II complex system [(Ce((R/S)-L)Br(μ-Br))₂]MnBr₄ [(R/S)-L = (2<i>R</i>,3<i>R</i>)- or (2<i>S</i>,3<i>S</i>)-2,3-dimethyl-1,4,7,10,13,16-hexaoxacyclooctadecane] with intra energy transfer from Ce^III to Mn^II, the luminescence dissymmetry factor of Mn^II obtained by excitation of Ce^III is around 10 times higher than that obtained by direct excitation of Mn^II, while the Ce^III center itself shows an almost negligible CPL. To address this unusual phenomenon, we proposed a new mechanism named structural relaxation chirality transfer (SRCT) where structural relaxation of the excited chiral donor amplified chirality transfer to the acceptor by intramolecular interactions. As an assistant proof, a mixture of Ce^III-Zn^II and La^III-Mn^II complexes with inter energy transfer showed no CPL amplification. These results will inspire more breakthroughs in the physics nature and development of energy-transfer induced CPL.