Far-infrared signatures of hydrogen bonding in phenol derivatives
Researchers from the FELIX Laboratory and the University of Gothenburg have applied gas-phase far-infrared spectroscopy by using the free electron laser FELIX to directly probe the intramolecular hydrogen-bond interaction in a family of phenol derivatives. The Journal of Physical Chemistry Letters published their results in March 2016.
Intra- and intermolecular hydrogen bonding plays a crucial role in, for example, solvation science, molecular recognition, and structure determination of neutral biomolecules. One of the most direct ways to study the intrinsic properties of the hydrogen-bond interaction is by gas-phase far-infrared (far-IR) spectroscopy because the vibrational modes involving hydrogen-bond deformation are excited by wavelengths in this spectral region. However, the far-IR regime is often ignored in molecular structure identification in the gas-phase due to the absence of strong far-IR light sources and difficulty in assigning the observed modes by quantum chemical calculations.
By using the free electron laser FELIX, far-IR/UV ion-dip spectroscopy was applied to directly probe the intramolecular hydrogen-bond interaction in a family of phenol derivatives. Three vibrational modes have been identified, which are expected to be diagnostic for the hydrogen-bond strength: hydrogen-bond stretching and hydrogen-bond-donating and -accepting OH torsion vibrations. Their position is evaluated with respect to the hydrogen bond strength, that is, the length of the hydrogen-bonded OH length. This shows that the hydrogen bond stretching frequency is diagnostic for the size of the ring that is closed by the hydrogen bond, while the strength of the hydrogen bond can be determined from the hydrogen-bond-donating OH torsion frequency. The combination of these two normal modes allows the direct probing of intramolecular hydrogen-bond characteristics using conformation-selective far-IR vibrational spectroscopy.
Reference:
Far-Infrared Signatures of Hydrogen Bonding in Phenol Derivatives
Daniël J. Bakker, Atze Peters, Vasyl Yatsyna, Vitali Zhaunerchyk, and Anouk M. Rijs
Journal of Physical Chemistry Letters 2016, 7, 1238−1243
DOI: 10.1021/acs.jpclett.6b00016
More information?
Daniel Bakker: d.bakker@science.ru.nl
Anouk Rijs: a.rijs@science.ru.nl