Resilient aromaticity in lead–indium clusters

The electronic structure of two particularly stable lead–indium clusters, namely PbIn 3 - and Pb2In2, has been studied by photoelectron spectroscopy and first-principles electronic structure calculations. Our studies reveal an enhanced stability of both PbIn 3 - and Pb2In2 clusters that can be classified within ‘all-metal aromaticity’. These clusters possess large gaps between the highest occupied and lowest unoccupied molecular orbitals (1.34 and 1.45 eV, respectively). Further, we show that despite the difference in electronegativities for lead and indium, the aromatic behavior is retained, and in the case of Pb2In2, aromaticity remains even after changes to the atomic arrangement of the planar cluster.