Probing the Structural and Electronic Properties of Dirhenium Halide Clusters: A Density Functional Theory Study

Dirhenium halide dianions received considerable attention in past decades due to the unusual metal-metal quadruple bond. The systematic structural evolution of dirhenium halide clusters has not been sufficiently studied and hence is not well-understood. In this work, we report an in-depth investigation on the structures and electronic properties of doubly charged dirhenium halide clusters Re₂X₈^2- (X = F, Cl, Br, I). Our computational efforts rely on the well-tested unbiased CALYPSO (Crystal structure AnaLYsis by Particle Swarm Optimization) method combined with density functional theory calculations. We find that all ground-state Re₂X₈^2- clusters have cube-like structures of D_4h symmetry with two Re atoms encapsulated in halogen framework. The reasonable agreement between the simulated and experimental photoelectron spectrum of the Re₂Cl₈^2- cluster supports strongly the reliability of our computational strategy. The chemical bonding analysis reveals that the δ bond is the pivotal factor for the ground-state Re₂X₈^2- (X = F, Cl, Br, I) clusters to maintain D_4h symmetric cube-like structures, and the enhanced stability of Re₂Cl₈^2- is mainly attributed to the chemical bonding of 5d orbital of Re atoms and 3p orbital of Cl atoms.