IR, Raman, and Vibrational Optical Activity Spectra of Methyl Glycidate in Chloroform and Water: The Clusters‐in‐a‐liquid Solvation Model

Abstract

Solvent effects, in particular those involving water as the solvent, are of significant interest to the chemistry and physics communities. IR, vibrational circular dichroism (VCD), Raman, and Raman optical activity (ROA) spectra of methyl glycidate in two very different solvents, namely CCl and water, have been measured experimentally and simulated theoretically. The observed spectra in CCl could be well modelled using the polarizable continuum model for the solvent, whereas the situation is much different in water. The experimental VCD spectrum of methyl glycidate in water reveals strong induced VCD signatures in the water bending region, indicating the presence of the relatively long-lived methyl glycidate-water complexes. We applied the clusters-in-a-liquid approach to identify the dominant methyl glycidate-water complexes which are the long-lived species responsible for all the spectra observed in water. We examined the influences of solvent dielectric environment and the hydrogen-bonding interactions on the conformational distribution of methyl glycidate. The geometry optimizations, frequency calculations, IR, VCD, Raman and ROA intensity calculations were performed at the B3LYP/6-311++G(2d,p) and aug-cc-pVTZ levels of theory with D3BJ dispersion correction. It is particularly satisfying to note that the clusters-in-a-liquid approach has captured all main experimental features in IR, VCD, Raman and ROA spectra of methyl glycidate in water.

Competition between inter and intramolecular hydrogen bond evidenced by vibrational circular dichroism spectroscopy: The case of (1S,2R)‐(−)‐cis‐1‐amino‐2‐indanol

“…The effect of entropy can also be assessed by comparing the spectra of Figures 5 and 7, obtained from the weighted average of all the conformational variants obtained for each family, with those considering only the most stable geometry of each family (Figures S4 and S5). The latter approach was used successfully by Perera et al and Weirich et al, with the weights of the different clusters obtained by adjustment to the experimental VCD spectrum 63,64 …”

“…The latter approach was used successfully by the groups of Xu and Merten, with the weights of the different clusters obtained by adjustment to the experimental VCD spectrum. 63,64…”

Raman Optical Activity of N‐Acetyl‐L‐Cysteine in Water and in Methanol: The “Clusters‐in‐a‐Liquid” Model and ab Initio Molecular Dynamics Simulations

“…[18,51] It was recognized in some studies that the hydrated clusters, which contain water hydrogen bonded networks, tend to produce very large, multi-signated, induced water VCD features at the water bending region. [24] Such strong characteristic VCD signals were rarely detected experimentally, leading to doubt about the existence of the long-lived species with extensive water hydrogen bonded network. This is a point which we will address further later on.…”

“…For example, in a recent study, the chiral solute was treated at the quantum mechanical level while the solvent layer with a radius of 6 Å from the solute was considered at the molecular mechanical level to evaluate vibrational optical activity of pantolactone. [19] A somewhat simplified approach, i. e. the "clusters-in-aliquid" solvation model, [21] emphasizes the long-lived solutesolvent clusters [22][23][24] and embeds these clusters in a solvation continuum. The induced solvent chirality features have provided the experimental evidence of the existence of long-lived solute-solvent clusters, and thus the foundation of the "clusters-in-a-liquid" model.…”

Use of Raman and Raman optical activity to extract atomistic details of saccharides in aqueous solution

“…Although there exist other calculation protocols to simulate Raman/ROA spectra [ 17 ], most of the state-of-the-art protocols nowadays consist of ensemble averaging many structures, usually tens to hundreds [ 12 , 16 , 18 , 19 ], generated with MD simulations. The microscopic structure of the first solvation layer (3–3.6 Å cutoff) was found to be very important [ 10 – 12 , 14 , 18 – 22 ], while the long-range polarization can be modeled either with continuum solvation methods or using a larger shell of explicit water molecules (10–12 Å cutoff) [ 13 , 19 ]. The spectra are then calculated for solute-solvent clusters at the DFT level, usually using the B3LYP or BPW91 functionals, with a sufficiently large basis set [ 10 , 23 ], e.g., 6–311++G** or aug-cc-pVTZ.…”