Objective:

To resolve the structure of a phosphoric acid dimer involved in proton transport and understand its hydrogen-bonding arrangement, which is crucial for its high proton conductivity.

Key Findings:

• A previously unreported structure for the phosphoric acid dimer was identified, termed A1, which is significant for understanding proton transport.
• The A1 structure features three hydrogen bonds across five oxygen atoms, including a unique motif with two hydroxyl groups coordinating to the same oxygen.
• Experimental spectra consistently supported the A1 structure over an alternative arrangement, reinforcing its relevance.

Interpretation:

The findings highlight the critical role of experimental validation in structural assignments, particularly when theoretical predictions yield closely related energy states.

Limitations:

• The study focused on a specific dimer and may not represent all phosphoric acid systems, potentially limiting the applicability of the findings.
• The reliance on spectral signatures may not capture all structural nuances, which could affect the interpretation of results.

Conclusion:

The identified structure A1 could serve as a benchmark for future quantum chemical models and enhance understanding of proton transfer in phosphoric acid systems, with implications for both biological processes and energy technologies.