Solid state magic angle spinning13C and31P NMR of organic ligand stabilized high nuclearity metal clusters

13C and31P solid state NMR measurements on the organic ligands in ligated Au55, Ni8, Pt309, Cu36 and Cu70 clusters are reported. The ligands behave like diamagnetic organic molecules, giving rise to relatively narrow lines with excellent cross-polarization efficiency. The resonance lines of the nuclei directly bound to the metal core are systematically broadened in the conducting compounds. No pronounced Knight shifts or evidence of metallic-like relaxation were observed. These results support a model for the electrical conduction involving tunneling between metal cores with the ligands playing the role of a tunneling barrier.