HyDRA II molecules
Below are the selected systems featured in the HyDRA II challenge. For comparison, free water has its symmetric stretching fundamental at 3657 cm-1. Note that in the challenge you will be asked to provide absolute wavenumbers for the complexes. If you directly calculate hydrogen bond induced downshifts, simply subtract those from the 3657 cm-1 experimental reference value for isolated water.
Challenge (test) set
The following are the main systems featured in the challenge. 1 stands for monohydrate OHb stretching wavenumbers, 2 for dihydrate OHb stretching wavenumbers. 2d for the water molecule directly coordinating the organic acceptor site and 2i for the second water molecule indirectly coordinating the organic acceptor site (see figures).| Molecule | Related works | abbreviation | CAS-number | Challenge bands |
|---|---|---|---|---|
Diisopropylethylamine
|
DPA | 7087-68-5 | 1, 2i | |
Eucalyptol |
EUC | 470-82-6 | 1 | |
2,6-Difluorobenzoic acid |
FBA | 385-00-2 | 1 | |
1-Pyrrolidineethanol |
PYE | 2955-88-6 | 1 | |
1-Methyl-4-iodo-1H-pyrazole |
IMP | 39806-90-1 | 1, 2d, 2i | |
2-Methoxypyridine |
[1] | MOP | 1628-89-3 | 1 |
2,6-Difluorobenzonitrile |
DFB | 1897-52-5 | 1 |
Bonus set
For the following systems, an unambiguous assignment might not be attained by the end of the challenge.
| Molecule | Related works | abbreviation | CAS-number | Challenge bands |
|---|---|---|---|---|
Tempone
|
OTM | 2896-70-0 | 1 | |
Diethylhydroxylamine |
[2] | DHA | 3710-84-7 | 1 |
Please note that experimental results will be provided directly after the deadline of the blind challenge. In each case we will make an effort to provide the best experimental mean field values for the OHb stretching fundamentals, with any obvious anharmonic resonances removed. These are the target wavenumbers for any computational treatment which ignores such anharmonic resonances (e.g. scaled harmonic, learning strategies, anharmonically corrected...) and they represent the base submission of the blind challenge.
From an experimental point of view, advanced methods which are able to reliably predict explicit anharmonic resonance patterns (e.g. variational treatments, coupling models...) would be particularly welcome. For those, we optionally ask for the prediction of the dominant eigenstate carrying spectral intensity in monohydrates. Together with its wavenumber (which will be somewhat off the mean field value or resonance polyad centroid, see e.g. https://doi.org/10.1039/D5CP00332F), the fraction of the total bright state intensity P (square of the OHb stretching wavefunction coefficient in the eigenstate) will be requested.
Example: if the base submission (center of the resonance polyad) for a given system is 3500cm-1, a possible optional computational result of the dominant signal might be 3490cm-1 with P=0.8 (in the case of a single resonance partner, that would mean that this resonance partner is predicted to show up in the spectrum at 3540cm-1 with P=0.2, because 3540*0.2+3490*0.8=3500).
