Vibrational Signatures of Chirality Recognition Between α‐Pinene and Alcohols for Theory Benchmarking

Abstract

Chirality recognition between largely rigid molecules can be applied as ab enchmark for the description of intermolecular forces by theoretical methods,b ecause one constituent is merely mirrored, so other deficits of the methods such as neglect of anharmonicity should mostly cancel. To test this approach, mixed OH···p-bridged dimers between the enantiomers of the bicyclic monoterpene a-pinene and the chiral secondary alcohols borneol, a-fenchol, isopinocampheol, and 1-phenylethanol were formed in as upersonic jet and probed by linear FTIR spectroscopy. With borneol and afenchol, pronounced shifts in the hydroxyl stretching frequencies upon exchange of the handedness are observed. From three tested density functionals,only B3LYP-D3(BJ) is able to predict these diastereomeric shifts in as atisfactory manner, while M06-2X and wB97X-D fall short.Chirality recognition, the ability of chiral objects to distin-Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

The reduced cohesion of homoconfigurational 1,2-diols

“…Alternatively, one could use spectral fingerprints to detect such CISS effects, because spectral trends may be more sensitive to deficiencies in theory than some energetical trends. 5 For the clusters of CD and ED, we have not observed any systematic chirality-sensitive deviations of B3LYP-D3 spectral predictions from experiment, although the dispersion at least at long range is treated in a force-field and thus spin-insensitive manner.…”

“…It has recently been argued that there is a fundamental energetical contribution with preference for homochiral pairings in the contact area between the molecules due to chirality-induced spin selectivity (CISS), 3 although the size of this effect remains quite uncertain 4 and it has not been detected unambiguously in the gas phase, so far. 5 It is therefore questionable whether this systematic effect will distort the otherwise expected more or less random preference for homoor heterochiral aggregation due to the individual interplay of electrostatic, induction, dispersion and Pauli forces for different molecules. We note that empirical evidence at the level of macroscopic crystals actually points to an opposite preference for heterochiral assemblies, 6 although perhaps not as pronounced as previously thought.…”