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Large amplitude motion within molecules trapped in solid parahydrogen


Molecules of the β-diketone and β-dialdehyde families were trapped in solid parahydrogen (pH2) to investigate the vibrational behavior of systems including an intramolecular hydrogen bond (IHB). In the simplest β-diketone, acetylacetone (AcAc), the H transfer related to the IHB is coupled with methyl torsions. In pH2, the study of the nuclear spin conversion (NSC) in methyl groups allows the characterisation of the influence of these large amplitude motions on the vibrational modes. The deuteration of the OH group involved in the IHB has important consequences on the vibrational spectrum of the molecule and evidence of NSC in methyl groups is difficult to get. In the chlorine derivative (3-chloroacetylacetone), the H-transfer is not anymore coupled with methyl torsion, and NSC has undetectable effects on the IR spectrum. A search of H tunneling splitting in the IR spectrocopy of β-dialdehydes trapped in pH2 was performed. A few modes of 2-chloromalonaldehyde appear as doublets and were assigned to tunnelling levels. The spectroscopic results related to large amplitude motions are detailed and discussed, highlighting puzzling effects.

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Publication details

The article was received on 23 Apr 2018, accepted on 23 May 2018 and first published on 23 May 2018

Article type: Paper
DOI: 10.1039/C8FD00080H
Citation: Faraday Discuss., 2018, Accepted Manuscript
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    Large amplitude motion within molecules trapped in solid parahydrogen

    A. Gutierrez-Quintanilla, M. Chevalier, J. Ceponkus, R. R. Lozada Garcia, J. Mestdagh and C. CREPIN, Faraday Discuss., 2018, Accepted Manuscript , DOI: 10.1039/C8FD00080H

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