Recent Advances in the Application of Vibrational Circular Dichroism Spectroscopy for the Characterization of Asymmetric Catalysts

Abstract

In this Minireview, we summarize our recent efforts to use vibrational circular dichroism (VCD) spectroscopy, the chiroptical version of IR spectroscopy, for the characterization of conformational preferences of asymmetric catalysts and complexes, formed upon the respective interactions or reactions of catalysts with substrates. After giving a brief overview of the general aspects of the technique, we showcase how VCD spectra of a chiral ion-pairing catalyst could be used to confirm a conformational shifting mechanism that determines the enan-[a]

Double Hydrogen Bonding Dimerization Propensity of Aqueous Hydroxy Acids Investigated Using Vibrational Optical Activity

“…The information about the structure and behavior of both acids provided by vibrational spectroscopies can be extended by their chiral variants: vibrational circular dichroism (VCD) − and Raman optical activity (ROA). , VCD and ROA detect small differences in, respectively, absorption and scattering of left- and right-circularly polarized light by chiral molecules. Both methods have proven their efficiency in providing unique fingerprint information about conformational behavior, higher-order structural arrangement, intermolecular interactions, and solvation that cannot be obtained from the corresponding unpolarized methods. − Nevertheless, works focusing on chiroptical features of carboxylic acids are rather rare. Merten et al studied the effect of solvation on conformation, hydrogen bonding, and dimerization propensities of several chiral, mostly aromatic, carboxylic acids using a combination of experimental and theoretical VCD. − Furthermore, there are two publications on ROA of tartaric acid (refs and ) but no reports of either VCD or ROA of malic acid and only few of lactic acid, − , including one structural study of polylactic acid .…”

Solvation of the Boc–Val–Phe–nPr peptide characterized by VCD spectroscopy and DFT calculations

“…3 As a chiroptical version of infrared (IR) spectroscopy, VCD spectroscopic signatures can be affected by intermolecular interactions. While this sensitivity can be exploited to characterize interactions in asymmetric catalysis [8][9][10][11][12][13] and biomolecules, 14,15 solute-solvent hydrogen bonding may cause unforeseen effects on the VCD spectra. 16,17 During an AC assignment, such solvent-influences are often discovered by accident; that means when the spectra calculations on the isolated target molecule do not match with the experimental signatures.…”

Anion-binding of a chiral tris(2-aminoethyl)amine-based tripodal thiourea: a spectroscopic and computational study

“…Crystallography and NMR spectroscopy are the most frequently used methods to characterize anion binding to thioureas. In the context of our work on asymmetric organocatalysts, 10 we recently used vibrational circular dichroism (VCD) spectroscopy, the chiroptical version of infrared spectroscopy, to gain more detailed insights into the solution phase conformational preferences of chiral thioureas and their hydrogen bonded complexes. [11][12][13] These and other studies demonstrated that VCD spectroscopy is very sensitive to interaction induced conformational changes.…”