A little while back, I wrote about anomeric-like effects in the sulfur ring S7.[1] I had started that exploration by retrieving the crystal structure from the ICSD (Inorganic crystal structure database) and then optimising these coordinates using a DFT method (MN15L/Def2-TZVPP to be precise). In demonstrating this effect to a student, I decided to create an initial guess for the molecule coordinates not from the crystal structure but by drawing and then minimising using a simple molecular mechanics force field – and only then subjecting it to DFT re-optimisation.[2] It turns out the result was quite surprising in one respect and so here I tell the rest of the story.
References
- H. Rzepa, "Cyclo-Heptasulfur, S<sub>7</sub> – a classic anomeric effect discovered during a pub lunch!", 2025. https://doi.org/10.59350/rzepa.28407
- H. Rzepa, "Anomeric isomerism in cyclo-heptasulfur.", 2026. https://doi.org/10.14469/hpc/15924