The reduced cohesion of homoconfigurational 1,2-diols

Beppo Hartwig (1) , Manuel Lange , Anja Poblotzki , Robert Medel , Anne Zehnacker (2, 3) , Martin Suhm

1 Institut für Physikalische Chemie [Göttingen]
2 ISMO - Institut des Sciences Moléculaires d'Orsay
3 SYSIPHE

By a combination of linear FTIR and Raman jet spectroscopy, racemic trans-1,2-cyclohexanediol is shown to form an energetically unrivalled S4-symmetric heterochiral dimer in close analogy to 1,2-ethanediol. Analogous experiments with enantiopure trans-1,2-cyclohexanediol reveal the spectral signature of at least three unsymmetric homochiral dimers. A comparison to signal-enhanced spectra of 1,2-ethanediol and to calculations uncovers at least three transiently homochiral dimer contributions as well. In few of these dimer structures, the intramolecular OHO contact present in monomeric 1,2-diols survives, despite the kinetic control in supersonic jet expansions. This provides further insights into the dimerisation mechanism of conformationally semi-flexible molecules in supersonic jets. Racemisation upon dimerisation is shown to be largely quenched under jet cooling conditions, whereas it should be strongly energy-driven at higher temperatures. The pronounced energetic preference for heterochiral aggregation of vicinal diols is also discussed in the context of chirality-induced spin selectivity.

Domaines: Chimie théorique et/ou physique

Beppo Hartwig, Manuel Lange, Anja Poblotzki, Robert Medel, Anne Zehnacker, et al.. The reduced cohesion of homoconfigurational 1,2-diols. Physical Chemistry Chemical Physics, 2020, 22 (3), pp.1122-1136. ⟨10.1039/c9cp04943f⟩. ⟨hal-02473832⟩