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 as well as the absence of environment effects allow for a direct comparison between computed and experimental spectra. This provides potential benchmarking data which can be revisited to hone different computational techniques, and it allows for the critical analysis of procedures under the setting of a blind challenge. In the latter case, the final result is unknown to modellers, providing an unbiased testing opportunity for quantum chemical models. In this work, we present the spectroscopic and computational results for the first HyDRA blind challenge. The latter deals with the prediction of water donor stretching vibrations in monohydrates of organic molecules. This edition features a test set of 10 systems. Experimental water donor OH vibrational wavenumbers for the vacuum-isolated monohydrates of formaldehyde, tetrahydrofuran, pyridine, tetrahydrothiophene, trifluoroethanol, methyl lactate, dimethylimidazolidinone, cyclooctanone, trifluoroacetophenone and 1-phenylcyclohexane-cis-1,2-diol are provided. The results of the challenge show promising predictive properties in both purely quantum mechanical approaches as well as regression and other machine learning strategies.
Version notes
Updated supporting information for submissions PH5 and AC4.
Content

Supplementary material

Experimental Supplementary Material
The experimental spectroscopic results on the 10 test monohydrates of the first HyDRA blind challenge. These were kept confidential until the final deadline for submission and editing of theoretical predictions, without any prior knowledge of the computed results of theory submissions.

Theoretical Supplementary Material
Complete report on all submissions evaluated against the experimental results.

Supporting Information for Submission AC1
Supplementary information with computational details and values for the submission labeled AC1 in the main manuscript.

Supporting Information for Submission AC2
Supplementary information with computational details and values for the submission labeled AC2 in the main manuscript.

Supporting Information for Submission AC3
Supplementary information with computational details and values for the submission labeled AC3 in the main manuscript.

Supporting Information for Submission AC4
Supplementary information with computational details and values for the submission labeled AC4 in the main manuscript. Furthermore, computational details and results for the water dimer are provided. The latter results were provided after disclosing the experimental test set results.

Supporting Information for Submission FA1
Supplementary information with computational details and values for the submission labeled FA1 in the main manuscript.

Supporting Information for Submission FA2
Supplementary information with computational details and values for the submission labeled FA2 in the main manuscript.

Supporting Information for Submission FA3
Supplementary information with computational details and values for the submission labeled FA3 in the main manuscript.

Supporting Information for Submission FA4
Supplementary information with computational details and values for the submission labeled FA4 in the main manuscript.

Supporting Information for Submission FA5
Supplementary information with computational details and values for the submission labeled FA5 in the main manuscript.

Supporting Information for Submission LS1
Supplementary information with computational details and values for the submission labeled LS1 in the main manuscript.

Supporting Information for Submission LS2
Supplementary information with computational details and values for the submission labeled LS2 in the main manuscript.

Additional Supporting Information for Submission LS2
Further Supplementary information with computational details and values for the submission labeled LS2 in the main manuscript. These results were provided after disclosing the experimental test set results.

Supporting Information for Submission LS3
Supplementary information with computational details and values for the submission labeled LS3 in the main manuscript.

Supporting Information for Submission LS4
Supplementary information with computational details and values for the submission labeled LS4 in the main manuscript.

Supporting Information for Submission PH1
Supplementary information with computational details and values for the submission labeled PH1 in the main manuscript.

Supporting Information for Submission PH2
Supplementary information with computational details and values for the submission labeled PH2 in the main manuscript.

Supporting Information for Submission PH3
Supplementary information with computational details and values for the submission labeled PH3 in the main manuscript.

Supporting Information for Submission PH4
Supplementary information with computational details and values for the submission labeled PH4 in the main manuscript.

Supporting Information for Submission PH5
Supplementary information with computational details and values for the submission labeled PH5 in the main manuscript. Furthermore, computational details and results for the water dimer are provided. The latter results were provided after disclosing the experimental test set results.

Supporting Information for Submission PH6
Supplementary information with computational details and values for the submission labeled PH6 in the main manuscript.

Supporting Information for Submission PH7
Supplementary information with computational details and values for the submission labeled PH7 in the main manuscript.
Supplementary weblinks
Experimental Supplement to the HyDRA blind challenge
The experimental spectroscopic results on the 10 test monohydrates of the first HyDRA blind challenge. These were kept confidential until the final deadline for submission and editing of theoretical predictions, without any prior knowledge of the computed results of theory submissions.
Submitted data to the first HyDRA blind challenge
Collection of data submitted to the first HyDRA blind challenge. This includes the individual submissions in json format and the corresponding supplementary information files (pdf) with computational details and values.