Photoconversion of Ag-31 to Ag-42 Initiated by Solvated Electrons

Light-matter interactions, especially in atomically precise nanomaterials, belong to an unexplored realm of research with potential benefits for the synthesis of materials. Here, we present an interesting light-activated expansion process of an Ag-31 nanocluster to an Ag-42 analogue, both clusters being protected with 6-(dibutylamino)-1,3,5-triazine-2, 4-dithiol (shortly, TRZ-H-2) ligands. The conversion process was initially monitored through UV-vis, revealing that the violet-colored Ag-31 got converted to greenish Ag-42, exhibiting their characteristic absorption features. High-resolution mass spectrometric studies confirmed that the as-synthesized [Ag-31(TRZ)(10)] with coexisting di- and monoanionic charged species in dichloromethane solution got converted to [Ag-42(TRZ)(13)] with a dipositive charge state. Electrochemical studies revealed the photoresponsive nature of Ag-31, and light illumination resulted in transient intermediate clusters covered with solvated electrons, which contributed to the core expansion. Ag-31 is NIR-emitting, while Ag-42 is red-emitting. The ultrafast transient absorption studies reveal that Ag-42 has strikingly short excited-state carrier dynamics than Ag-31. The stable excited-state carriers for Ag-31 upon photoexcitation also underline the unique electronic characteristics responsible for such light-activated structural evolution.