Imaging an unsupported metal-metal bond in dirhenium molecules at the atomic scale.

Cao, Kecheng; Skowron, Stephen T; Biskupek, Johannes; Stoppiello, Craig T; Leist, Christopher; Besley, Elena; Khlobystov, Andrei N; Kaiser, Ute · Sci Adv · 2020

basic_science · Level V

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Abstract

Metallic bonds remain one of the most important and least understood of the chemical bonds. In this study, we generated Re<sub>2</sub> molecules in which the Re-Re core is unsupported by ligands. Real-time imaging of the atomic-scale dynamics of Re<sub>2</sub> adsorbed on a graphitic lattice allows direct measurement of Re-Re bond lengths for individual molecules that changes in discrete steps correlating with bond order from one to four. Direct imaging of the Re-Re bond breaking process reveals a new bonding state with the bond order less than one and a high-amplitude vibrational stretch, preceding the bond dissociation. The methodology, based on aberration-corrected transmission electron microscopy imaging, is shown to be a powerful analytical tool for the investigation of dynamics of metallic bonding at the atomic level.