Furan solvation

The challenge will have a double-blind character: The experimental results in test will not be available beforehand. Theoreticians and experimentalists alike will not be informed about the other groups’ data until the results are all jointly revealed. This will help in protecting the data and guaranteeing the independence of the results.

The systems considered in this challenge are the dimers of furan/methanol, 2-methylfuran/methanol and 2,5-dimethylfuran/methanol. The complex of methanol with 2,5-dimethylfuran provides a starting point. Our experiments indicate a slight preference for oxygen coordination (doi:10.1039/c6cp05413g). Rough DFT calculations (see the supplementary information) indicate a slight trend towards carbon (or π) coordination of the methanol OH group with stepwise de-methylation of the furan scaffold.

This is an invitation to theory groups to use their own (or any other available) methods to investigate this trend. The goal is to present the best possible predictions for the energy difference (at 0K) between the two possible modes of binding.

Rules

The rules are as follows:

  1. The challenge will officially start on 01/11/2016. From this date onward entries to the challenge will be accepted.
  2. An entry initially only consists of the written statement that relevant predictions have been obtained (a short general designation of the used methods is required, but can be changed at a later time). The registration is carried out at the GoeBench website (www.goebench.net). No submission is required at this time.
  3. The final entry date is set to 31/01/17.
  4. A participant can register more than one entry. This will correspond to different approaches to the calculation.
  5. Between 01/02/17 and 15/02/17, the data for each entry (submission) has to be delivered by the respective participant.
  6. Experimental data for the complex of methanol with 2,5-dimethylfuran has already been published and can be used by the participants as test (doi:10.1039/c6cp05413g).
  7. A submission consists of at least:
    1. a best structure (Cartesian coordinates) for both binding motives (O/ π-bound) of all three dimers
    2. an energy difference between the two motives (electronic + zero-point energy correction) in kJ/mol
    3. a precise description of the computational protocol used, enough to guarantee reproducibility
    participants may, however, also include:
    1. further minimum structures corresponding to O/π/otherwise bound dimers
    2. IR (an-)harmonic OH stretching wavenumber in cm-1 and absorption strength for the OH stretching fundamental in km/mol
    3. change in the energy spacing (and wavenumber and absorption strength) upon substitution of methanol by methanol-D1
    4. energy decomposition schemes trying to explain the predicted subtle preference in terms of different interaction energy types (e.g., polarization, dispersion)
    5. dipole components along the principal axes for microwave verification of the structures
    6. minimal barriers connecting the two lowest structures of O- and π-bound complexes
  8. The submission data will be subject to review. If any inconformity is found, the participant may be contacted.
  9. On the 01/02/17, all entries will be made public on the website. Also, the experiments on the furan/ and 2-methylfuran/methanol dimers will begin. These may face unexpected difficulties (band overlap, limited signal-to-noise, instrumental failure, excessive barriers between conformations) but should normally be completed successfully in February 2017. The submitted theoretical data will not be disclosed to the experimentalists before completion of the experiments.
  10. Upon completion of the experiments, all data will be made available at the GoeBench site and a joint publication will be prepared (including all participants with valid submissions in the spirit of the challenge).
  11. The small size of the system, of the sample, and of the targeted energy difference all discourage entries which profit from major error compensation or lack important physical ingredients. If the number of entries exceeds 10-15, the organizers reserve the right to select the most adequate submissions for joint publication and leave others for optional separate individual publication. However, method diversity in the joint publication is welcome in view of possible further rounds of this challenge including a broadened experimental data base.
  12. Any participant is free to remove their entry at any time, or even to exclude themselves from the joint publication.

In order to guarantee the double blind character, the registration and overview of the submissions will be handled by Ricardo Mata. Predictions of other suitable substituted furan-alcohol pairs for further rounds of this challenge are highly welcome, but will have to be screened for availability and expected experimental practicability, before they may eventually enter a next round.