Ligand-protected gold nanoclusters probed by IRMPD spectroscopy and quantum chemistry calculations

•Structures of isolated kilodalton ligand-protected gold nanoclusters are studied.•By means of gas-phase InfraRed Multiple Photon Dissociation spectroscopy compared to quantum chemistry calculations.•Nanocluster complexes consist of ten or eleven gold atoms that are bound to glutathione or phosphine ligands.•Theoretical calculations are able to reproduce well the experimental IR spectra, although the size of such species makes difficult a precise assignment among the many possible molecular arrangements.