Published in Henry Rzepa's Blog

In the earlier post on the topic of anomeric effects, I identified a number of outliers associated with large differences in the lengths of two carbon-oxygen bonds sharing a common carbon atom. Here is another of these outliers (MUZZIS[cite]10.1107/S2056989016002899[/cite]) which shows equally unusual properties.

References

Condensed Matter PhysicsGeneral Materials ScienceGeneral Chemistry

Bis(benzyltrimethylammonium) bis[(4SR,12SR,18RS,26RS)-4,18,26-trihydroxy-12-oxido-13,17-dioxaheptacyclo[14.10.0.03,14.04,12.06,11.018,26.019,24]hexacosa-1,3(14),6,8,10,15,19,21,23-nonaene-5,25-dione] sesquihydrate: dimeric structure formationvia[O—H—O]negative charge-assisted hydrogen bonds (–CAHB)with benzyltrimethylammonium counter-ions

Published in Acta Crystallographica Section E Crystallographic Communications
Authors Ravell Bengiat, Maayan Gil, Asne Klein, Benny Bogoslavsky, Shmuel Cohen, Joseph Almog

The reaction between bis-ninhydrin resorcinol and benzyltrimethylammonium fluoride in ethanol has produced the title compound, 2C10H16N+·2C24H13O8−·1.5H2O, which contains a unique centrosymmetric supramolecular dimeric entity, where two deprotonated ligands are held togetherviatwo strong and short [O...O = 2.4395 (13) Å] [O—H—O]−bonds of the typenegative charge-assisted hydrogen bonds (–CAHB). The central aromatic rings of the ligands create parallel-displaced π–π stacking at an interplanar distance of 3.381 (1) Å, which helps stabilize the dimer. In the crystal, two symmetry-related solvent water molecules with a site occupancy of 0.75 are attached to the carbonyl groups of the dimer by weaker O—H...O hydrogen bonds, forming chains along [101].