High‐Resolution Absorption and Electronic Circular Dichroism Spectra of (R)‐(+)‐1‐Phenylethanol. Confident Interpretation Based on the Synergy between Experiments and Computations

Abstract

Using density functional theory and its time-dependent extension for excited states, the S →S high-resolution vibronic absorption and electronic circular dichroism spectra of (R)-(+)-1-phenylethanol are computed and compared to experimental spectra measured in jet-cooled conditions in the region within 1000 cm of the 0-0 transition. The agreement between theory and computation is satisfactory and allows a confident assignment of several experimental bands in terms of fundamentals of different modes. Cases are documented for which the analysis of optical anisotropy factors, owing to their signed nature, remarkably enhances the possibility of a robust assignment of the experimental absorption bands. Computational analysis shows that the experimental spectra are dominated by Herzberg-Teller contributions and that the electronic circular dichroism spectrum and the anisotropy factors are also strongly modulated by the effect of Duschinsky mixings.

Spectroscopy for model heterogeneous asymmetric catalysis

“…In the course of the latter work, theoretical calculations predicted the presence of a vibronic band which was originally not resolved in the experiments. Based on those predictions, the experiments were recorded with a higher resolution and, interestingly, the predicted band could be resolved, and its anisotropy factor was shown to be correctly predicted, as demonstrated in Figure …”

“…In an exemplary fruitful work between theoreticians and experimentalists, together with Santoro, we revealed another benefit of CD‐REMPI‐MS studies on jet‐cooled molecules . Based on vibronically resolved spectra of 1‐phenylethanol, the anisotropy factors of the molecule were calculated, and it was found that the assignment of vibronic transitions could be done with higher confidence when experimental anisotropy factors are also taken into account .…”

“…In other words, the actual catalyst (eg, the metal cluster supported on a chiral support) needs to uptake a sense of handedness which can be utilized during the reaction. Inducing chirality from a chiral molecule into an originally achiral compound was reported around six decades ago, among others, in interactions of achiral solutes and chiral solvents . It was observed that the UV bands of the solute molecules show circular dichroism as the result of complexation with the chiral solvent.…”

“…Consequently determining the performance of the catalyst requires highly sensitive chiroptical spectroscopic techniques that are capable of revealing the enantiomeric excess (ee) of the products quickly and reliably in the gas phase. In our group, we have taken steps in both directions and have developed a set of sensitive chiroptical techniques that are suitable for the study of surfaces [58][59][60][61][62] and dilute gas samples [63][64][65][66] chiroptically.…”

“…Inducing chirality from a chiral molecule into an originally achiral compound was reported around six decades ago, among others, in interactions of achiral solutes and chiral solvents. [66][67][68][69][70] It was observed that the UV bands of the solute molecules show circular dichroism as the result of complexation with the chiral solvent. Since not all the optical transitions are always monitored, the absence of optical activity in optical transitions that unambiguously belong to the catalyst does not necessarily equate to lack of chirality transfer.…”