A Theoretical Perspective on the Bond Length Rule of Grochala, Albrecht, and Hoffmann

Grochala, Albrecht, and Hoffmann have recently observed that, for many organic and inorganic molecules, the bond lengths in the cation (R +), neutral system (R gs), first triplet excited state (R es), and anion (R -) approximately satisfy R + + R - − R gs − R es ≈ 0. This paper shows how the Fukui function, a concept from the density functional theory of chemical reactivity, can be used to rationalize the Grochala−Albrecht−Hoffmann rule. The treatment also suggests which types of chemical systems will be best described by the Grochala−Albrecht−Hoffmann rule.