The first HyDRA challenge for computational vibrational spectroscopy

Abstract

Vibrational spectroscopy in supersonic jet expansions is a powerful tool to assess molecular aggregates in close to ideal conditions for the benchmarking of quantum chemical approaches. The low temperatures achieved...

Gauging ambiphilicity of pseudo-halidesviaberyllium-trispyrazolylborato compounds

“…The harmonic frequency calculations generally overestimate the experimental values. 41 Thus, the respective bands are calculated at 2291 ([TpBe(CN)]), 2240 ([TpBe(N 3 )]), 2358 ([TpBe(NCO)]) and 2165 cm −1 ([TpBe(NCS)]). These bands are hypsochromically shifted compared to those computed for free pseudo halides (Table 4).…”

Investigating the Spectroscopy of the Gas Phase Guanine–Cytosine Pair: Keto versus Enol Configurations

“…To this aim, we employ vibrational spectroscopy because the effects of hydrogen bonding can be easily detected through it, and non-trivial information can be extracted when the vibrational spectra of hydrogen-bonded species are compared to the corresponding non-bonded species. − Therefore, the experimental vibrational spectra of nucleobase dimers are interesting and well-known in the gas phase, where the hydrogen bond contribution to the pair formation and stability can be isolated from the π stacking and hydrophobic interaction. The hydrogen-bonded structure is observed only in the gas phase, because in aqueous solution, the bases prefer the stacked disposition. , The vibrational spectra could also help to clarify if any proton hopping is taking place, in particular in the guanine–cytosine pair, by inspecting if specific features of the proton-hopped tautomer are present in the spectra. ,− The main current limitation of these experiments is the absence of a solid and thorough assignment of the main spectral features, which would allow one to clearly identify the corresponding tautomer.…”

“…The QCT spectrum is able to include the potential energy surface anharmonicity, but it cannot collect any quantum effect. Nonetheless, it provides affordable and important data and has been applied with success to several systems. ,, …”

Microhydration of Tertiary Amines: Robust Resonances in Red-Shifted Water

“…15 Some of the signals observed there might actually be due to mixed trimers, similar to the situation for water clusters. 9,22 This invites a direct comparison of the two techniques for the same species in future work. One should also revisit an interpretation of matrix-isolated water − trimethylamine spectra, 29 which invoked a cluster of two amine and four water units to explain a triplet similar to the one observed in this work, together with some absorptions in the CH region.…”

“…This forms an excellent playground for anharmonic models of hydrogen-bonded water molecules, bridging the regular dynamics of weaker hydrogen bonds of water, e.g., to alcohols or ketones and the heavily coupled dynamics of carboxylic acid complexes . It also defines an interesting challenge for the reliable prediction of OHb frequencies when the hydrogen bonding becomes stronger. Other than for phenol–amine complexes that can be accessed via truly size-selective methods, there is a clear separation of the OH vibrations from CH vibrations in the 1:1 complexes, which helps in the assignment.…”