Ln 3+ Induced Thermally Activated Delayed Fluorescence of Chiral Heterometallic Clusters Ln 2 Ag 28 .

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 ΔE(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.