Anomalous Diamagnetic Susceptibility in 13‐Atom Platinum Nanocluster Superatoms

We are used to being able to predict diamagnetic susceptibilities χ_D to a good approximation in atomic increments since there is normally little dependence on the chemical environment. Surprisingly, we find from SQUID magnetization measurements that the χ_D per Pt atom of zeolite‐supported Pt₁₃ nanoclusters exceeds that of Pt²⁺ ions by a factor of 37–50. The observation verifies an earlier theoretical prediction. The phenomenon can be understood nearly quantitatively on the basis of a simple expression for diamagnetic susceptibility and the superatom nature of the 13‐atom near‐spherical cluster. The two main contributions come from ring currents in the delocalized hydride shell and from cluster molecular orbitals hosting the Pt 5d and Pt 6s electrons.