Tailoring Superatomic Stability with Transition Metals in Silicon Cages: Shrinking to M@Si<sub>15</sub> (M = Re, Os, Ir)
Takumi Ichikawa, Kazuya Terasaka, Ayaka Sasaki, Atsushi Nakajima
Abstract
High Resolution Image Download MS PowerPoint Slide The design of materials with intriguing electronic properties is crucial for advancing nanoscale technologies, where precise control over atomic structure and electronic behavior is essential. Metal-encapsulating silicon cage superatoms (SAs) provide a new paradigm for molecular-scale material design, allowing fine-tuning of both structure and electronic characteristics. The formation of superatoms mimicking halogens, noble gases, and alkali metals has been well-studied, particularly with M@Si 16, where early transition metals from groups 3 to 5 stabilize within a Si 16 cage, achieving a 68-electron configuration. For late transition metals with excess electrons, a Si 15 cage offers enhanced stability by fulfilling the 68-electron rule with one fewer Si atom. This research synthesizes Si 15 cage-SAs with rhenium (Re) from group 7 and iridium (Ir) from group 9 on p -type and n -type organic substrates. The stability of Re@Si 15 and Ir@Si 15 is evaluated via oxidative reactivity with X-ray photoelectron spectroscopy and theoretical calculations, including osmium (Os) from group 8. Re@Si 15 –, Os@Si 15 0, and Ir@Si 15 + exhibit superatomic behaviors similar to halogens, noble gases, and alkali metals due to the 68-electron shell closure. Among them, Re@Si 15 – on p -type organic substrates shows superior electronic and geometric properties. These findings advance our understanding of M@Si n systems for transition metals, addressing longstanding questions about their properties at n = 15 and 16.