Spectroscopic Signatures of Low‐Barrier Hydrogen Bonding in Neutral Species

Proton-Tunneling Dynamics along Low-Barrier Hydrogen Bonds: A Full-Dimensional Instanton Study of 6-Hydroxy-2-formylfulvene

“…Given the manifest importance of proton-transfer processes in chemistry and biochemistry, significant attention has focused on species containing intramolecular LBHBs, and their ability to discern the most salient geometric and electronic features that govern hydron migration. Recently, 6-hydroxy-2-formylfulvene (HFF) has emerged as a prototypical model system for the study of low-barrier hydrogen bonding (LBHBing) and associated hydron-transfer dynamics in neutral molecules. − As shown in Figure , HFF is characterized by a seven-membered reaction site in which a strong O···H···O intramolecular interaction is stabilized by π-electron conjugation with a cyclopentadiene ring. An atypical quasilinear hydrogen bond spans the short distance connecting hydroxymethylene (proton-donating) and formyl (proton-accepting) moieties, with a small potential-energy impediment for proton migration of ∼800 cm –1 giving rise to a vibrational ZPE that putatively straddles the barrier crest .…”