We report a joint experimental and theoretical study of two luminescent molecular quantum clusters of silver, Ag7(H2MSA) 7 and Ag8(H2MSA)8 (H2MSA is the dicarboxylic acid of mercaptosuccinic acid in thiolate form). Global optimizations and property calculations are performed in the framework of density-functional theory (DFT-PBE) to search for the leading candidates with the lowest energy. The simulated excitation spectra of these two clusters are in good agreement with the corresponding experimental spectra. The presence of -RS-Ag-RS- as a stable motif has been confirmed in all of the lowest energy structures. © 2011 American Chemical Society.