Quantum Crystallography Refinement of [18]-Annulene Structure

Henry Rzepa from Imperial College London re-refined the crystal structure of [18]-annulene using quantum crystallography methods. The dataset likely contains refined atomic coordinates and thermal parameters derived using the Def2-SVP basis set and wB97X-V method within the OLEX2 program. The published structure was found to be disordered with two molecular orientations in an approximately 84:16 ratio.

Use Cases

• Benchmarking quantum crystallography refinement protocols based on the described staged refinement process.
• Analyzing molecular disorder and occupancy ratios in planar macrocycles based on the described 84:16 disorder.
• Studying the stability of hydrogen atom positions during anisotropic refinement based on the described 'wandering off' behavior.

Strengths

• Structure is based on a published CCDC entry (refcode ANULEN03), providing a known reference point.
• Refinement details are explicitly documented, including the basis set (Def2-SVP) and method (wB97X-V).
• Describes a specific methodological solution to a refinement instability problem.

Limitations

• Column-level documentation is absent; field semantics must be inferred after download.
• Row count is unknown, which may limit suitability assessment.
• Last update date is unknown; freshness unverified.

Provenance

Source

Imperial College London

Collection Method

Re-refinement of a published crystal structure using quantum crystallography techniques in OLEX2.