1. DOING THE LIMBO WITH A LOW BARRIER: Hydrogen Bonding and Proton Transfer in 6-Hydroxy-2-Formylfulvene
ZPE
Zero Point Energy
ZPE
Zachary N. Vealey, Deacon J. Nemchick, Lidor Foguel, & Patrick H. Vaccaro
Department of Chemistry, Yale University
225 Prospect St., New Haven, CT USA

2. Reaction Coordinate Potentials
Weak Bond
Intermediate Bonds
Strong Bond
A Spectroscopic Metric for Proton-Transfer Rate
A············H—D
A·············H—D
D—H············A
A·········H········A
D—H············A
D—H·············A
Symmetric Well
with High Barrier
Symmetric Well
with Low Barrier
Symmetric Well
with No Barrier
Asymmetric Well
HFF
6-Hydroxy-2-FormylFulvene

3. 6-Hydroxy-2-Formylfulvene (HFF)
No Barrier
Low Barrier
vs.
Symmetric EQ Structure
Asymmetric EQ Structure
Bulk-gas MW
Δ ≈ 150 ± 20 cm-1
Rapid 100 fs
proton-transfer rate
Liquid NMR/IR studiesb
Bulk-gas XPSc
Supports discrete
proton-transfer dynamics a
b C. L. Perrin and B. K. Ohta., Bioorg. Chem. 30(1), 3-15 (2002).
a H. M. Pickett, J. Am. Chem. Soc. 95(6), (1973).
c R. S. Brown, et. al, J. Am. Chem. Soc. 101 (12), (1979).

4. Experimental Setup
Trot << 5 K
Spectral Resolution ~ 0.06 cm–1

5. U.S. National Science Foundation
Summary & Conclusions
HFF affords a model system for exploring the synergism between proton transfer and low-barrier hydrogen bonding.
Vibronically-resolved information has been obtained for the ground and (π*π) excited states of HFF and HFF-d.
LIF spectra show extensive excited-state progressions built upon modes that modulate the reaction site.
DF spectra reveal evidence of ground-state tunneling dynamics characterized by and
Multiple-resonance spectroscopy (FHB, SEP, RFWM) will be deployed to elucidate vibrational landscapes and tunneling dynamics.
Weakly bound complexes formed with hydrogen-bonding and inductively-coupled ligands will be interrogated to explore incipient solvation effects.
Supported by:
U.S. National Science Foundation