Domino Tunneling

Peter R. Schreiner, J. Philipp Wagner, Hans Peter Reisenauer, Dennis Gerbig, David Ley, János Sarka, Attila G. Császár, Alexander Vaughn, Wesley D. Allen

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

Matrix-isolation experiments near 3 K and state-of-the-art quantum chemical computations demonstrate that oxalic acid [1, (COOH)2] exhibits a sequential quantum mechanical tunneling phenomenon not previously observed. Intensities of numerous infrared (IR) bands were used to monitor the temporal evolution of the lowest-energy O-H rotamers (1cTc, 1cTt, 1tTt) of oxalic acid for up to 19 days following near-infrared irradiation of the matrix. The relative energies of these rotamers are 0.0 (1cTc), 2.6 (1cTt), and 4.0 (1tTt) kcal mol-1. A 1tTt → 1cTt → 1cTc isomerization cascade was observed with half-lives (t1/2) in different matrix sites ranging from 30 to 360 h, even though the sequential barriers of 9.7 and 10.4 kcal mol-1 are much too high to be surmounted thermally under cryogenic conditions. A general mathematical model was developed for the complex kinetics of a reaction cascade with species in distinct matrix sites. With this model, a precise, global nonlinear least-squares fit was achieved simultaneously on the temporal profiles of nine IR bands of the 1cTc, 1cTt, and 1tTt rotamers. Classes of both fast (t1/2 = 30-50 h) and slow (t1/2 > 250 h) matrix sites were revealed, with the decay rate of the former in close agreement with first-principles computations for the conformational tunneling rates of the corresponding isolated molecules. Rigorous kinetic and theoretical analyses thus show that a "domino" tunneling mechanism is at work in these oxalic acid transformations. (Graph Presented).

Original languageEnglish
Pages (from-to)7828-7834
Number of pages7
JournalJournal of the American Chemical Society
Volume137
Issue number24
DOIs
Publication statusPublished - Jun 24 2015

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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    Schreiner, P. R., Wagner, J. P., Reisenauer, H. P., Gerbig, D., Ley, D., Sarka, J., Császár, A. G., Vaughn, A., & Allen, W. D. (2015). Domino Tunneling. Journal of the American Chemical Society, 137(24), 7828-7834. https://doi.org/10.1021/jacs.5b03322