Ln3+ Induced Thermally Activated Delayed Fluorescence of Chiral Heterometallic Clusters Ln2Ag28

A series of TADF‐active compounds: 0D chiral Ln−Ag(I) clusters L ‐/ D ‐Ln 2 Ag 28 ‐0D (Ln=Eu/Gd) and 2D chiral Ln−Ag(I) cluster‐based frameworks L ‐/ D ‐Ln 2 Ag 28 ‐2D (Ln=Gd) has been synthesized. Atomic‐level structural analysis showed that the chiral Ag(I) cluster units {Ag 14 S 12 } in L ‐/ D ‐Ln 2 Ag 28 ‐0D and L ‐/ D ‐Ln 2 Ag 28 ‐2D exhibited similar configurations, linked by varying numbers of [Ln(H 2 O) x ] 3+ ( x =6 for 0D, x =3 for 2D) to form the final target compounds. Temperature‐dependent emission spectra and decay lifetimes measurement demonstrated the presence of TADF in L‐ Ln 2 Ag 28 ‐0D (Ln=Eu/Gd) and L ‐Gd 2 Ag 28 ‐2D . Experimentally, the remarkable TADF properties primarily originated from {Ag 14 S 12 } moieties in these compounds. Notably, {Ag 14 S 12 } in L ‐Eu 2 Ag 28 ‐0D and L ‐Gd 2 Ag 28 ‐2D displayed higher promote fluorescence rate and shorter TADF decay times than L ‐Gd 2 Ag 28 ‐0D . Combined with theoretical calculations, it was determined that the TADF behaviors of {Ag 14 S 12 } cluster units were induced by 4 f perturbation of Ln 3+ ions. Specially, while maintaining Δ E (S 1 –T 1 ) small enough, it can significantly increase k (S 1 →S 0 ) and reduce TADF decay time by adjusting the type or number of Ln 3+ ions, thus achieving the purpose of improving TADF for cluster‐based luminescent materials.