Relativistic Effects Stabilize the Planar Wheel-like Structure of Actinide-Doped Gold Clusters: An@Au7 (An = Th to Cm).

Abstract

Despite the chemistry of actinide-ligand bonding is continuing and of burgeoning interest, investigations of the chemical bonding of bimetallic complexes involving transuranics remain relatively less, and there are rarely studies on the bonding features between actinide and coinage metals (CM). We present a systematic research on the series of An@Au7 (An = Th to Cm), UCM7 (CM = Cu, Ag, Au), and WAu7 clusters to investigate the unique geometries, electronic structures, and chemical bonding between An 5f6d orbitals and CM ns orbitals, and to find their periodicity across the actinides and within the group of transition metals. A unique planar wheel-like structure for An@Au7 clusters with the help of actinide metals encapsulation via spin-orbit coupling, resulting in An(III). Instead, the transition-metal (TM) element W retains its usual six-gold-coordination structure in WAu7, thus forcing the seventh Au out of plane. The An-CM interactions, depending on the ion radii, become stronger with the increase of the atomic number of the actinide metals, as well as the CM. These results show that the presence of actinides in clusters can lead to unique electronic and geometrical structures.