Chirality transfer through hydrogen-bonding: Experimental and ab initio analyses of vibrational circular dichroism spectra of methyl lactate in water

Abstract

The infrared vibrational absorption (VA) and vibrational circular dichroism (VCD) spectra of methyl lactate were measured in the 1000-1800 cm(-1) region in the CCl(4) and H(2)O solvents, respectively. In particular, the chirality transfer effect, i.e. the H-O-H bending bands of the achiral water subunits that are hydrogen-bonded to the methyl lactate molecule exhibit substantial VCD strength, was detected experimentally. A series of density functional theory calculations using B3PW91 and B3LYP functionals with 6-311++G(d,p) and aug-cc-pVTZ basis sets were carried out to simulate the VA and VCD spectra of the methyl lactate monomer and the methyl lactate-(H(2)O)(n) complexes with n = 1, 2, 3. The population weighted VA and VCD spectra of the methyl lactate monomer are in good agreement with the experimental spectra in CCl(4). Implicit polarizable continuum model was found to be inadequate to account for the hydrogen-bonding effect in the observed VA and VCD spectra in H(2)O. The methyl lactate-(H(2)O)(n) complexes with n = 1, 2, 3 were used to model the explicit hydrogen-bonding. The population weighted VA and VCD spectra of the methyl lactate-H(2)O binary complex are shown to capture the main spectral features in the observed spectra in aqueous solution. The theoretical modeling shows that the extent of chirality transfer depends sensitively on the specific binding sites taken by the achiral water molecules. The observation of chirality transfer effect opens a new spectral window to detect and to model the hydrogen-bonding solvent effect on VCD spectra of chiral molecules.

Chirality Recognition between Neutral Molecules in the Gas Phase

“…In all three cases, chirality information is transferred from the chiral object to the molecule and may be detected at the molecule itself for example, by electronic [153] or vibrational circular dichroism techniques. [154,155] Vibrational circular dichroism is difficult to study for clusters in the gas phase, [156] but it may be applied to matrix-isolated systems, [157] where complexes can be investigated. Chirality induction is at the heart of modern asymmetric organic synthesis.…”

Adenine versus guanine quartets in aqueous solution: dispersion-corrected DFT study on the differences in π-stacking and hydrogen-bonding behavior

“…The continuum solvent model performs adequately for the determination of geometries as has been done in this work. However, for the calculation of spectra of molecules in a solvent, it is essential to take into account the first shell of solvent molecules explicitly [63][64][65][66][67][68][69]. For instance, Nicu et al [63] showed that the VCD spectrum of 2-benzoic acid is influenced by the hydrogen bonding with the solvent due to the donor-acceptor interaction (which of course is not taken into account by continuum solvent models).…”

Signatures of counter-ion association and hydrogen bonding in vibrational circular dichroism spectra

“…[7][8][9][10][11] Specific solute-solvent interactions (e.g. hydrogen-bonding or counter-ion complexation) need to be entered explicitly in the quantum mechanical calculations.…”