Vibrational specificity of proton-transfer dynamics in ground-state tropolone.
The vibrational dependence of large-amplitude proton transfer taking place in the ground electronic state (X1A1) of tropolone has been explored by implementing a coherent variant of the stimulated emission pumping (SEP) technique within the framework of two-color resonant four-wave mixing (TC-RFWM) spectroscopy. The lowest 1700 cm(-1) portion of this potential surface has been interrogated under ambient bulk-gas conditions, enabling rotationless term energies (Tv+) and tunneling-induced bifurcations Delta(v)X to be extracted for 43 assigned vibrational features of a1 and b2 symmetry. The resulting values of Delta(v)X reflect the state-specificity long attributed to the hydron-migration pathways of tropolone and range in magnitude from 0.0 cm(-1) to 17.8 cm(-1), where the former implies essentially complete quenching of unimolecular dynamics whilst the latter represents nearly a twenty-fold increase in reaction rate over that of the zero-point level. This vibrational mediation of tunneling behavior is discussed in terms of attendant atomic displacements and permutation-inversion symmetries, with choreographed motion of the five-member reaction site (C-O-H...O=C) found to exert the most significant influence on the efficacy of proton transfer.
Murdock
Daniel
D
Department of Chemistry, Yale University, P. O. Box 208107, New Haven, CT 06520-8107, USA.
Burns
Lori A
LA
Vaccaro
Patrick H
PH
D011522:Protons; D011789:Quantum Theory; D013816:Thermodynamics; D014334:Tropolone / Q000737:chemistry*; D014732:Vibration
D011522:Protons; D014334:Tropolone