If there is evidence for anharmonic resonances affecting the OH stretching mode, the raw wavenumber value (`OHb raw´) for the dominant spectroscopic signal (upper graph) is complemented by another, deperturbed value (lower graph) which corresponds to the intensity centroid (`OHb deperturbed´), implying that resonance partners carry negligible intrinsic intensity (dark state approximation). Quoted uncertainties can be unsymmetric (error+, error-) and represent estimated uncertainties of the dominant signal position (raw) and of the intensity centroid position (deperturbed). The intensity fraction of the dominant signal (`fraction OHb character´) is given for predictive models which explicitly address the resonances. For all other (mean field) predictions, it is recommended to target the intensity centroid (`OHb deperturbed´). Currently, three types of OHb stretching vibrations are listed (`OHb class´):
`1´: hydrogen-bonded OH stretching vibration of a single water coordinating the target molecule in monohydrates.
`2d´: hydrogen-bonded OH stretching vibration of a directly coordinating water molecule in a dihydrate.
`2i´: OH stretching vibration of the second water molecule when it primarily coordinates the 2d water molecule and only indirectly the target molecule.

All information refers to the global minimum structures of the mono- and dihydrates in the sense that there is no other known arrangement of the water molecules around the target molecule with a lower energy. The target molecule in the hydrate complexes may be in a different conformation than in vacuum isolation, but configurational adaptions involving high barriers (such as cis/trans isomerism in carboxylic acid or ester groups) are not expected to occur in the experiments. The DOI of a key reference for the experimental results is given. Other relevant literature is provided in the `Comment´ section, together with additional useful information.

The database may serve as a training platform for future HyDRA blind challenges. Hydrogen bond-induced redshifts from the water monomer symmetric stretching vibration may be calculated by subtracting the OH stretching fundamental wavenumber from 3657cm^-1.