Abstract

Size and shape determination of ultrasmall gold superatoms passivated by protecting ligands, is a fundamental concern towards the obtention of efficient tunable building blocks. In this report, we pursue a further understanding of the energetic terms ruling the core-shape determination in the first two 2-cluster electron gold selenido clusters reported to date. Our results show that the ultrasmall [Au8Se2(L)(4)](2+) series featuring an Au-4 tetrahedron with two separated exo Au2Se units (core type a), and a Au-4 tetrahedron with two connected Au2Se units resulting in a distorted hexagonal Au-6 ring (core type b), obtained for L = PPh2CH2PPh2 (dppm) and L = PPh2(CH2)(2)PPh2 (dppe), respectively. The more favorable a(dPPm) arrangement by 5.7 kcal.mol(-1) over b(dPPm), by the less repulsive Pauli repulsion term by 13.9 kcal.mol(-1), and the more stabilizing electrostatic character (29.4 kcal.mol(-1)), and London dispersion (12.4 kcal.mol(-1)), despite the more favorable contribution from orbital interactions and solvation (-46.4 kcal.mol(-1), and, -3.6 kcal.mol(-1), respectively) in the later. For b(dPPe )arrangement, a more favorable situation is found by 11.5 kcal.mol(-1) in comparison to a(dPPe), determined by the leads to a more stabilizing contribution from electrostatic (31.5 kcal.mol(-1)), orbital (1.8 kcal.mol(-1)), London dispersion (11.9 kcal.mol(-1)) contributions, despite to offer a more steric hindered situation. Such structural preference is in line with experimental findings, allowing comparison of the relative stability of clusters bearing different ligand layers, enabling further shape-property relationship exploration in gold clusters. In addition, optical spectrum features are evaluated. Lastly, sulfido and tellurido hypothetical counterparts denote similar structural preferences.