Zachary N. Vealey, Lidor Foguel, & Patrick H. Vaccaro Proton Transfer and Low-Barrier Hydrogen Bonding: Shifting Vibrational Landscapes Dictated by Large Amplitude Tunneling Zachary N. Vealey, Lidor Foguel, & Patrick H. Vaccaro Department of Chemistry, Yale University 225 Prospect St., New Haven, CT 06520 USA

Proton Transfer and Tunneling Deceptively simple migration of hydron between donor and acceptor sites Tunneling Coordinate Relative Intensity MA Unimolecular transformation represents a prototypical chemical reaction 6-Hydroxy-2-Formylfulvene (HFF) Model systems provide valuable insight for dynamics in much larger entities TrOH Tunneling-mediated pathways promoted by the small mass of labile proton Proton-Transfer Rate: Continuum of Hydrogen Bonding and Tunneling Dynamics Low-Barrier Hydrogen Bond

Calculated Barriers and Structures M06-2X/aug-cc-pVDZ H or D CCSD/aug-cc-pVDZ Global Minimum Transition State CCSD/aug-cc-pVDZ

Experimental Setup

U.S. National Science Foundation Summary & Conclusions ~ PROBED A1B2 LOWEST-LYING SINGLET ELECTRONIC STATE OF HFF LIF spectra show extensive excited-state progressions of rxn-modulating modes Small (~24°) out-of-plane distortion predicted for transition-state geometry Rotational band-contour analyses reveal dramatic quenching of proton transfer INTERROGATED X 1A1 GROUND ELECTRONIC STATE OF HFF DF spectra reveal largest-ever reported vibrationless tunneling splitting Large magnitude tunneling reflected in mode-specific dynamics DKIE highlight continuum between tunneling and barrierless reaction dynamics ~ ONGOING AND FUTURE WORK Deploy multiple resonance techniques (SEP & RFWM) to elucidate ground state Investigate proton-transfer channels in neighboring electronic states of HFF Explore dynamics in weakly bound complexes built on the HFF scaffold WD02 Supported by: U.S. National Science Foundation