Effects of complexation with sulfuric acid on the photodissociation of protonated Cinchona alkaloids in the gas phase

Abstract

The complex formed between Cinchona alkaloids and sulphuric acid consists of a doubly protonated Cinchona alkaloid strongly bound to a bisulphate HSO4− anion. This structure explains the lack of photo-reactivity of the complex upon UV irradiation.

Chiral discrimination between tyrosine and β-cyclodextrin revealed by cryogenic ion trap infrared spectroscopy

“…IR-UV double resonance spectroscopy is not possible for the complexes of -MCD studied here because they are stable upon UV irradiation due to the cage effect of -MCD, already observed in other systems. [35][36][37] The reported spectra are obtained by IRPD of the H2-tagged complexes. Figures 3c and d show the vibrational spectra of the L-TyrH + --MCD and D-TyrH + --MCD complexes, respectively.…”

Setting up the HyDRA blind challenge for the microhydration of organic molecules

“…Ultimately, one must hope for a number of systematically successful models which connect theory and experiment on multiple observables, not only the vibrational wavenumber. Meaningful approximations such as elaborate scaling techniques, 22,23 local mode models, 24,25 parameterised harmonic DFT predictions, 26 ab initio molecular dynamics, 27 polarisable force fields 28 or hierarchical models building on high level treatments of the smallest systems or subgroups 29 may be identified or we may even witness the victory of machine-learning approaches 30 towards such challenges.…”

Do Stereochemical Effects Overcome a Charge-Induced Perturbation in Isolated Protonated Cyclo(Tyr-Tyr)?

“…Also, the bound ν­(OH + ) frequency is calculated at different frequencies for c-LLH + and c-LDH + , reproducing the lower frequency observed for c-LDH + , which in turn reflects a stronger OH + ···π interaction. The downshift of the bound ν­(OH + ) frequency is underestimated for both diastereomers, which is a deficiency of the currently used method for modes involved in strong hydrogen bonds. , However, the D3­(BJ) correction performs slightly better in this respect by shifting the calculated value further down in energy, thus closer to the experimental value. With both D3 and D3­(BJ) corrections, the smaller redshift of ν­(OH) in c-LLH + relative to c-LDH + correlates well with the strength of the OH + ···π interaction, as reflected by the distance between the proton and the center of the aromatic ring mentioned above.…”