A luminescent Ag₈(DPPY)₆(PhCC)₆ cluster with a triangular superatomic Ag₈ core

We have synthesized single crystals of a highly stable Ag₈ nanocluster protected by six ligands of diphenyl-2-phosphinic pyridine (DPPY) plus six ligands of phenylacetylene (PhCC). This Ag₈(DPPY)₆(PhCC)₆ cluster bears a triangular superatomic Ag₈ core, with the vertex and edge Ag atoms (quasi-triangle Ag₆) being protected by both P and N bidentate coordination of the six DPPY ligands; meanwhile, the six PhCC ligands via μ₃-C coordination form coordination on the two central Ag atoms capped on both sides of the triangle facet. Apart from the well-organized coordination of the two ligands pertaining to the balanced interactions with the Ag₈ core, this Ag₈ nanocluster exhibits superatomic stability with two delocalized valence electrons (1S²||1P⁰), assuming that the six PhCC ligands fix 6 localized electrons from the Ag atoms. Interestingly, the Ag₈(DPPY)₆(PhCC)₆ NCs display temperature-dependent dual emissions at 330 and 535 nm under deep ultraviolet excitation. TD-DFT calculations reproduced the experimental spectrum, shedding light on the nature of excitation states and metal-ligand interactions in such a superatomic metal cluster.