Doping the cage. Re@Au11Pt and Ta@Au11Hg, as novel 18-ve trimetallic superatoms displaying a doped icosahedral golden cage

Abstract

Expanding the versatility of well defined clusters is a major concern in the design of building blocks towards functional nanostructures. W@Au₁₂ is a prototypical binary bare superatomic cluster involving an icosahedral symmetry, which has been discussed in the literature, precluding the proposal of several endohedral d-block and f-block element structures within a golden cage. Here we pursue the construction of related trimetallic clusters, which has been explored to a lesser extent. Our results expose the great advantages of involving heterocages in the superatom approach, unraveling Re@Au₁₁Pt and Ta@Au₁₁Hg as novel trimetallic candidates. Re@Au₁₁Pt exhibits an electron-deficient element in the cage, and an endohedral atom with an extra electron. In contrast, Ta@Au₁₁Hg is conceived as having an icosahedral cage with an extra electron, and an electron-deficient endohedral element. These new clusters follow the eighteen valence electron principle, with similar characteristics to their W@Au₁₂ parent. This leads to stable clusters with an electronic structure formally described by the 1s²1p⁶1d¹⁰ closing shell order, showing an interesting approach to design ternary superatoms, where the variation of valence electrons occurs in both cage and endohedral sites. Moreover, the cage doping appears as a useful approach to further evaluate the formation of magnetic superatoms, and also the construction of larger clusters by fusing different icosahedral structures.