[Ag23Pd2(PPh3)10Cl7]0: A new family of synthesizable bi-icosahedral superatomic molecules.

Icosahedral noble-metal 13-atom nanoclusters (NCs) can form connected structures, which can be regarded as superatomic molecules, by vertex sharing. However, there have been very few reports on the superatomic molecules formed using silver (Ag) as the base element. In this study, we synthesized [Ag23Pd2(PPh3)10Cl7]0 (Pd = palladium, PPh3 = triphenylphosphine, Cl = chloride), in which two icosahedral 13-atom NCs are connected, and elucidated its geometric and electronic structures to clarify what type of superatomic molecules can be synthesized. The results revealed that [Ag23Pd2(PPh3)10Cl7]0 is a synthesizable superatomic molecule. Single crystal x-ray diffraction analysis showed that the metal-metal distances in and between the icosahedral structures of [Ag23Pd2(PPh3)10Cl7]0 are slightly shorter than those of previously reported [Ag23Pt2(PPh3)10Cl7]0, whereas the metal-PPh3 distances are slightly longer. On the basis of several experiments and density functional theory calculations, we concluded that [Ag23Pd2(PPh3)10Cl7]0 and previously reported [Ag23Pt2(PPh3)10Cl7]0 are more stable than [Ag25(PPh3)10Cl7]2+ because of their stronger superatomic frameworks (metal cores). These findings are expected to lead to clear design guidelines for creation of new superatomic molecules.