Inverse Solid-State Photoluminescence and Electrochemiluminescence of Isostructural Nanoclusters: Unveiling the Critical Role of Intermolecular Charge Migration.

Atomically precise metal nanoclusters are promising electrochemiluminescent (ECL) materials. However, the correlation between their solid-state photoluminescence (PL) and ECL remains ambiguous, severely hindering the rational design of high-performance solid-state ECL materials. Herein, we report two nanoclusters, Au5Ag13(DPPP)4(C6F5S)10 and [AuxAg17-x ((DPPP)5(C6F5S)8]SbF6, which share an identical Au5Ag8 metal core but differ slightly in peripheral motifs, thus exhibiting a striking inverse solid-state PL-ECL relationship. Single-crystal structures and Hirshfeld surface analysis reveal that the stronger π-π interactions and higher molecular packing density in (AuAg)18 facilitate efficient intermolecular electron transfer and charge migration, which are more critical than excited-state generation and annihilation during the ECL process. This work demonstrates that charge transfer between nanoclusters and the electrode surface outweighs intrinsic excited-state annihilation and decay in solid-state ECL, providing a new mechanistic guideline for designing high-performance ECL materials beyond the traditional pursuit of strong PL.