Discrete Ru(Sn)₆ Octahedra Encapsulated in Oxoindate Channels: RuSn₆In₆O₁₆ with Highly Ordered In/Sn Sites

A new transition metal–mixed main group element cluster compound, RuSn6In6O16, was prepared via the tin-flux method. Single-crystal structure refinements show that RuSn6In6O16 crystallizes in a monoclinic crystal system with a centrosymmetric C2/m space group. It shows a unique structure type reminiscent of metal–organic framework (MOF) structures. The structure exhibits a highly positive [Ru(Sn)6]14+ metallic cluster (guest) encapsulated in an oxoindate framework (host) formed by a combination of corner- and edge-sharing InO6/InO7 polyhedra. The oxidation states were experimentally and theoretically determined to be Ru2+ and Sn2+ in the metallic cluster and In3+ in the oxide layers. The cluster shows a direct band gap like that of semiconducting materials, which was also confirmed by band structure calculations. The photoluminescence spectrum exhibits a peak at 455 nm (blue emission), which may originate from oxygen vacancies in the microcrystalline powder. This indicates that RuSn6In6O16 has the potential to be used in light-emitting diodes (LEDs) and photovoltaic applications.